Subtask2_4_HandHModelingReport

Subtask 2.4: Hydrologic and
Hydraulic Modeling Gap Analysis
North Carolina Flood Resiliency Blueprint
Prepared for the North Carolina Department of Environmental Quality by AECOM and
ESP Associates
October 2023
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | i
Table of Contents
Definitions ...................................................................................................................... iv
Acronyms ......................................................................................................................... v
1 Introduction ............................................................................................................... 1
2 State Agency Datasets ................................................................................................. 3
2.1 North Carolina Floodplain Mapping Program Regulatory Riverine Modeling .......................... 3
2.2 North Carolina Emergency Management Base Level Modeling .............................................. 13
2.3 North Carolina Emergency Management Dam Breach Modeling ............................................ 18
2.4 North Carolina Dam Safety and NCEM Dam Overtopping Modeling ....................................... 20
2.5 North Carolina Emergency Management Basin Mitigation Modeling ..................................... 24
2.6 North Carolina Dam Safety Emergency Action Plan Breach Modeling ................................... 26
2.7 North Carolina Department of Transportation Hydraulic Design Modeling ........................... 28
2.8 North Carolina Department of Transportation Resiliency Studies ......................................... 29
2.9 North Carolina Department of Environmental Quality Basin-wide Hydrologic Modeling ..... 31
2.10 North Carolina Department of Environmental Quality Water Quality Modeling .................... 33
2.11 North Carolina Floodplain Mapping Regulatory Coastal Modeling......................................... 35
3 Other North Carolina Models ..................................................................................... 37
3.1 County and Municipality Modeling ........................................................................................... 37
3.2 United States Army Corps of Engineers River Basin Feasibility Studies ................................. 38
3.3 Other Potential Modeling Sources ............................................................................................ 40
4 Nationwide/Regional Datasets .................................................................................. 42
4.1 NOAA Office of Water Prediction National Water Model .......................................................... 42
4.2 National Weather Service River Forecast Centers ................................................................... 44
4.3 Pacific Northwest National Laboratory Rapid Infrastructure Flood Tool ............................... 46
4.4 United States Geological Survey National Hydrologic Model ................................................. 48
4.5 United States Army Corps of Engineers South Atlantic Coastal Study ................................... 50
4.6 National Oceanic and Atmospheric Administration Sea, Lake, and Overland Surges
from Hurricanes Modeling ........................................................................................................ 51
4.7 University of North Carolina Renaissance Computing Institute ADCIRC Prediction
System Modeling ....................................................................................................................... 54

North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | ii
Figures
Figure 1: NCFMP Regulatory Modeling Age ................................................................................................. 5
Figure 2: NCFMP Regulatory Modeling Scale (Coverage) ............................................................................ 6
Figure 3: NCFMP Regulatory Modeling % Detailed Study ........................................................................... 6
Figure 4: NCEM Base Level Modeling Scale (Coverage) ............................................................................ 15
Figure 5: NCEM Dam Breach Modeling Spatial Extent .............................................................................. 19
Figure 6: NCEM Dam Overtopping Modeling Spatial Extent ..................................................................... 22
Figure 7: Completed NCEM River Basin Studies ........................................................................................ 25
Figure 8: NCDEQ Basin-wide Hydrologic Modeling Status ....................................................................... 32
Figure 9: The NWM provides statewide current and forecast streamflow estimates. ............................. 42
Figure 10: NWS River Forecast Regions across the Nation ....................................................................... 44
Figure 11: PNNL RIFT Modeling Output for Hurricane Florence ............................................................... 47

Tables
Table 1: NCFMP Regulatory Modeling Dataset Information ....................................................................... 4
Table 2: NCFMP Regulatory Modeling Gap Analysis Criteria Description .................................................. 4
Table 3: NCFMP Regulatory Modeling Gap Analysis Criteria ...................................................................... 7
Table 4: NCFMP Regulatory Modeling Data Gaps...................................................................................... 12
Table 5: NCEM Base Level Modeling Dataset Information ........................................................................ 13
Table 6: NCEM Base Level Modeling Gap Analysis Criteria Description ................................................... 14
Table 7: NCEM Base Level Modeling Gap Analysis Criteria ....................................................................... 15
Table 8: NCEM Base Level Modeling Data Gaps ........................................................................................ 17
Table 9: NCEM Dam Breach Modeling Dataset Information ..................................................................... 18
Table 10: NCEM Dam Breach Modeling Gap Analysis Criteria Summary ................................................. 19
Table 11: NCEM Dam Breach Modeling Data Gaps .................................................................................... 20
Table 12: NCEM Dam Overtopping Modeling Dataset Information .......................................................... 21
Table 13: NCEM Dam Overtopping Modeling Gap Analysis Criteria Summary ........................................ 21
Table 14: NCEM Dam Overtopping Modeling Data Gaps .......................................................................... 22
Table 15: NCEM Basin Mitigation Modeling Dataset Information ............................................................ 24
Table 16: NCEM Basin Mitigation Modeling Gap Analysis Criteria Summary ........................................... 24
Table 17: NCEM Basin Mitigation Modeling Data Gaps ............................................................................. 25
Table 18: NC Dam Safety Emergency Action Plan Breach Modeling Dataset Information ...................... 26
Table 19: NC Dam Safety Emergency Action Plan Breach Modeling Gap Analysis Criteria
Summary ................................................................................................................................. 27
Table 20: NC Dam Safety Emergency Action Plan Breach Modeling Data Gaps ...................................... 27
Table 21: NCDOT Hydraulic Design Modeling Dataset Information ......................................................... 28
Table 22: NCDOT Hydraulic Design Modeling Gap Analysis Criteria Summary ....................................... 28
Table 23: NCDOT Hydraulic Design Modeling Data Gaps .......................................................................... 29
Table 24: NCDOT Transportation Resiliency Modeling Dataset Information .......................................... 30
Table 25: NCDOT Transportation Resiliency Modeling Gap Analysis Criteria Summary ......................... 30
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | iii
Table 26: NCDOT Transportation Resiliency Modeling Data Gaps ........................................................... 31
Table 27: NCDEQ Basin-wide Hydrologic Modeling Dataset Information ................................................ 31
Table 28: NCDEQ Basin-wide Hydrologic Modeling Gap Analysis Criteria Summary .............................. 32
Table 29: NCDEQ Basin-wide Hydrologic Modeling Data Gaps ................................................................ 33
Table 30: NCDEQ Water Quality Modeling Dataset Information .............................................................. 33
Table 31: NCDEQ Water Quality Modeling Gap Analysis Criteria Summary ............................................. 34
Table 32: NCDEQ Water Quality Modeling Data Gaps ............................................................................... 34
Table 33: NCFMP Regulatory Coastal Modeling Dataset Information ...................................................... 35
Table 34: USGS NHM Modeling Gap Analysis Criteria Summary .............................................................. 35
Table 35: NCFMP Regulatory Coastal Modeling Data Gaps ...................................................................... 36
Table 36: County and Municipality Modeling Dataset Information.......................................................... 37
Table 37: County and Municipality Modeling Gap Analysis Criteria Summary ........................................ 37
Table 38: County and Municipality Modeling Data Gaps .......................................................................... 38
Table 39: USACE River Basin Feasibility Modeling Dataset Information .................................................. 39
Table 40: USACE River Basin Feasibility Modeling Gap Analysis Criteria Summary ................................ 39
Table 41: USACE River Basin Feasibility Modeling Data Gaps .................................................................. 40
Table 42: NOAA NWM Modeling Dataset Information ............................................................................... 42
Table 43: NOAA NWM Modeling Gap Analysis Criteria Summary ............................................................. 43
Table 44: NOAA NWM Modeling Data Gaps ................................................................................................ 43
Table 45: NWS River Forecast Centers Modeling Dataset Information .................................................... 44
Table 46: NWS River Forecast Centers Modeling Gap Analysis Criteria Summary................................... 45
Table 47: NWS River Forecast Centers Modeling Data Gaps ..................................................................... 45
Table 48: PNNL RIFT Modeling Dataset Information ................................................................................ 46
Table 49: PNNL RIFT Modeling Gap Analysis Criteria Summary ............................................................... 46
Table 50: PNNL RIFT Modeling Data Gaps ................................................................................................. 47
Table 51: USGS NHM Modeling Dataset Information ................................................................................ 48
Table 52: USGS NHM Modeling Gap Analysis Criteria Summary .............................................................. 49
Table 53: USGS NHM Modeling Data Gaps ................................................................................................ 49
Table 54: USACE SACS Coastal Modeling Dataset Information ................................................................ 50
Table 55: USACE SACS Coastal Modeling Gap Analysis Criteria Summary .............................................. 51
Table 56: USACE SACS Coastal Modeling Data Gaps................................................................................. 51
Table 57: NOAA SLOSH Modeling Dataset Information ............................................................................ 52
Table 58: NOAA SLOSH Modeling Gap Analysis Criteria Summary ........................................................... 52
Table 59: NOAA SLOSH Modeling Data Gaps ............................................................................................. 53
Table 60: RENCI ADCIRC Modeling Dataset Information .......................................................................... 54
Table 61: RENCI ADCIRC Modeling Gap Analysis Criteria Summary ......................................................... 55
Table 62: RENCI ADCIRC Modeling Data Gaps ........................................................................................... 55

North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | iv
Definitions
A comprehensive list of definitions applicable to multiple Flood Resiliency Blueprint documents is
provided in a separate document.

North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | v
Acronyms
2D – Two Dimensional
ADCIRC – Advanced Circulation (coastal surge
model)
AEP – Annual Exceedance Probability
APS – ADCIRC Prediction System
APSViz – APS visualization application
CERA – Coastal Emergency Risk Assessment
DFIRM - Digital Flood Insurance Rate Map
EAP – Emergency Action Plan
ERDC – United States Corps of Engineers
Engineering Research and Development
Center
FEMA – Federal Emergency Management
Agency
FIS - Flood Insurance Study
FRIS – Flood Risk Information System
HEC-HMS – Hydrologic Engineering Center
Hydrologic Modeling System; Open-source
model developed by the United States Army
Corps of Engineers
HEC-RAS – Hydrologic Engineering Center
River Analysis System; Open-source model
developed by the United States Army Corps of
Engineers
H&H – Hydrology and Hydraulics
HUC – Hydrologic Unit Code
ICM – Integrated Catchment Modeling;
Proprietary model developed by InfoWorks
ICPR – Interconnected Channel and Pond
Routing; Proprietary model developed by
Streamline Technologies
LiDAR - Light Detection and Ranging
MWBM - Monthly Water Balance Model
NA – Not Available
NC – North Carolina
NCDEQ – North Carolina Department of
Environmental Quality
NCDOT – North Carolina Department of
Transportation
NCEM – North Carolina Emergency
Management
NCFMP – North Carolina Floodplain Mapping
Program
NHC – National Hurricane Center
NHM – National Hydrologic Model
NOAA – National Oceanic and Atmospheric
Administration
NWM – National Water Model
NWS – National Weather Service
OASIS – Options Analysis in Irrigation Systems;
Open-Source model developed by Dr. Nicolas
Roost
P-Surge – Probabilistic Storm Surge model
PNNL – Pacific Northwest National Laboratory
PRMS - Precipitation-Runoff Modeling System
RENCI – Renaissance Computing Institute
RIFT – Rapid Infrastructure Flood Tool
SACS - South Atlantic Coastal Study
SDP - SLOSH Display Program
SFC – State Floodplain Compliance
SLOSH – Sea Lake and Overland Surges from
Hurricanes (coastal surge model)
SLR – Sea Level Rise
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SMS – Surface-water Modeling System;
Proprietary model developed by Aquaveo
SRH-2D – Sediment and River Hydraulics –
Two Dimension; Open-Source model
developed by the US Bureau of Reclamation
STWAVE – Steady-state spectral Wave model
SWAN – Simulated Waves Nearshore (coastal
wave model)
SWAT – Soil and Water Assessment Tool
UNC – University of North Carolina
US – United States
USACE – United States Army Corps of
Engineers
USGS – United States Geological Survey
WRF – Weather Research and Forecasting
XPSWMM – Stormwater Wastewater
Management Model; Proprietary model
developed by XP Software (additional versions
by Innovyze and Aqauveo)

North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 1
1 Introduction
Purpose: Subtask 2.4 – Report on Hydrology and Hydraulic (H&H) modeling studies: age, scale,
level of detail, modeling platform (e.g., open source or proprietary), flood hazards modeled, and
considerations for future risk.
The intent of this document is to identify and evaluate H&H modeling within North Carolina that could
be available for use in projects performed as part of the North Carolina Flood Resiliency Blueprint
(Blueprint). Specifically, this document is intended to provide a Gap Analysis for H&H modeling
available within the state, including those developed as part of resiliency assessments . Efforts were
made to capture all H&H modeling that could be made available through coordination with Blueprint
stakeholders and that either already had associated products that could support evaluation and
decision-making regarding proposed projects intended to reduce flood impacts projects or could be
used to develop such products . H&H modeling information is a critical component of a successful
flood resiliency effort. Results and data from H&H modeling provide valuable flood hazard
information that is necessary to perform risk assessments for events with known probability of
occurrence. Risk assessments link the flood hazards identified in the H&H modeling to estimated
damages enabling the evaluation of the effectiveness of mitigation and resiliency projects. Combined
with risk assessments, H&H modeling products, when presented correctly, also provide valuable
outreach opportunities to stakeholders for project understanding and buy-in.
For purposes of this document, H&H models can be broken down into the following categories:
• Hydrologic Models: Input-output models that simulate the water cycle using the water balance
equation. These models can focus on flow (quantity) as well as chemical/physical properties
(quality) of water. When used for flood studies, the models calculate runoff that occurs during a
precipitation event . Input parameters typically include precipitation (volume and timing
distribution) and runoff parameters based on soil and landcover data. The models use a variety of
methods to transform the rainfall into runoff and provide flow data (peak, volume, and timing) as
an output .
• Hydraulic Models: Input-output models that use flow data obtained from hydrologic models to
calculate streamflow characteristics including water surface elevation, depth and width of water,
and velocity. Hydraulic models rely heavily on accurate topographic data and hydraulic
parameters such as the Manning’s roughness coefficient, a value that represents a surface’s
resistance to flow. Hydraulic models can further be broken down into one- and two-dimensional
(2D). One-dimensional models assume flow only moves in one general direction (upstream to
downstream), whereas 2D models calculate flow in any lateral direction. One-dimensional models
are generally simpler and easier to use but limited in extent (most only model a single reach of a
stream). Two-dimensional models often cover a large area and can be setup to include all the
potential flooding sources within that area. Some 2D models have now integrated hydrologic
calculations with the hydraulic model which can reduce the effort of translating hydrologic model
output to a hydraulic model input. Two-dimensional models do require more intensive processing
and may take several hours to calculate depending on the size and level of detail.
Both hydrologic and hydraulic models may be open source (free to use) or proprietary (pay for license
to use). Proprietary models may provide enhanced features or products that some stakeholders find
valuable, but their use can be limited if licenses are required . In general, open-source models provide
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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 2
comparable features and products to proprietary models and are widely used/accepted within the
flood modeling community .
This document will overview the H&H modeling sources identified in this effort and note gaps that
exist within the dataset pertaining to the following criteria: age, scale (spatial extent), level of detail,
modeling platform availability, flood hazards modeled, and considerations for future risk.
North Carolina Flood Resiliency Blueprint

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2 State Agency Datasets
2.1 North Carolina Floodplain Mapping Program Regulatory
Riverine Modeling
Beginning in the year 2000, North Carolina became the first Cooperating Technical State with the
Federal Emergency Management Agency (FEMA) in the management of the National Flood Insurance
Program. This partnership resulted in one of the most well-known and pro-active statewide floodplain
mapping programs. The North Carolina Floodplain Mapping Program (NCFMP) has performed flood
insurance studies (FISs) to update digital flood insurance rate maps (DFIRMs) across the entire state
and is currently in a map maintenance phase.
Studies are performed with varying levels of detail including:
• Detailed - Multiple flood events with varying probability of occurrence (also known as flood
profiles) analyzed with regulatory floodway (the channel of a stream and the adjacent land area
that must be reserved in order to discharge the base flood with cumulatively increasing the water
surface elevation more than a designated height) and field survey of hydraulic structures (bridges,
culverts, dams, levees) and cross sections incorporated into model geometry. This is the highest
level of study performed for regulatory modeling for FEMA.
• Limited Detail – A 1-percent-annual-chance profile (also known as the 100-year flood or base
flood) only modeled with advisory non-encroachment area (the portion of the floodplain where
construction, placement of fill, or similar alteration of topography may be prohibited by a
community due to the effects such development would have on the conveyance of discharge) and
field or light detection and ranging (LiDAR) based measurements and photos of hydraulic
structures (no field survey). This level of study is less accurate than “detailed” but can be
performed at reduced effort/cost . The hydraulic structures (e.g., bridges, culverts) may be
somewhat crude due to the lack of survey data and the channel dimensions are typically
approximated.
• Approximate – A 1 percent-annual-chance (100-year or base flood) floodplain delineation with no
base flood elevations determined (also called unnumbered Zone A). Often these studies lack a
model entirely or depend on a model with no hydraulic structures or field survey incorporated.
These studies can be significantly out of date and inaccurate. They have largely been replaced but
can still be found in parts of the state. The original floodplain delineations may have been based on
soil maps or other information.
• Redelineation – Older detailed studies that used older models (typically HEC-2). These studies
include multiple flood events with varying probabilities whose model results have been re-mapped
on updated topographic data. Although originally based on detailed survey data available at the
time of model production, these studies can be significantly out of date and are gradually being
replaced with new models.
The NCFMP developed an enterprise database to house the supporting data associated with the flood
mapping efforts including field survey, H&H modeling and results, and mapping products necessary
for the development of the FISs and DFIRMs. This data is available through the Flood Risk Information
System (FRIS) website. Table 1 provides summary information for the NCFMP regulatory modeling
dataset.
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 4
Table 1: NCFMP Regulatory Modeling Dataset Information
NCFMP Regulatory Riverine Modeling
Source of Information North Carolina Emergency Management – Floodplain Mapping Program
Link to Online Data https://fris.nc.gov/fris/Home.aspx?ST=NC
Data Owner State of North Carolina
Date Created 2000
Date of Access February 2023
Frequency of Updates Annual funding for cyclical updates throughout the state
Update Needed Yes – Regular updates necessary to maintain reliable products

Table 2 below describes the criteria used to perform the gap analysis. The actual criteria are
presented in Table 3.
Table 2: NCFMP Regulatory Modeling Gap Analysis Criteria Description
Criteria Description
Age The average age of models available from currently effective studies.
Scale (Spatial Extent) The dataset is statewide. To better gauge modeling coverage, the total miles of
regulatory study within each hydrologic unit code (HUC) 8 is compared to the
total estimated miles of streams draining ½ square mile (considered to be a
minimum drainage area feasible for a regulatory H&H model) and calculated as
a %.
Level of Detail The % of study performed with each study type; Detailed, Limited Detail,
Approximate, and Redelineation.
Modeling Platform
Availability
Open source (free to use) or proprietary (pay for license) modeling software.
Flood Hazards
Modeled
Flood recurrence interval events analyzed.
Future Conditions The % of miles with future conditions compared to the total estimated miles of
streams draining ½ square mile . For purposes of this dataset, future conditions
are based on build-out conditions and do not include any climate change
considerations.

The requested gap analysis criteria were analyzed by summarizing the statewide H&H model
information available in the NCFMP enterprise database by 8-digit hydrologic unit code (HUC 8).
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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 5
Figure 1, Figure 2, and Figure 3 below present the regulatory modeling dataset’s age, scale (coverage),
and level of detail (percent detailed study) summarized by HUC 8. Table 3 summarizes the gap
analysis criteria by HUC 8.

Figure 1: NCFMP Regulatory Modeling Age
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Figure 2: NCFMP Regulatory Modeling Scale (Coverage)

Figure 3: NCFMP Regulatory Modeling % Detailed Study
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Table 3: NCFMP Regulatory Modeling Gap Analysis Criteria
HUC 8
Age
(yrs)
Scale
(%) Level of Detail (%)
Modeling
Platform
Availability
Flood
Hazards
Modeled
Future
Conditions
(%)
03010102 16 45% Detailed: 17.8%
Limited Detail: 82.1%
Redelineation: 0.1%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03010103 15 62% Detailed: 4.4%
Limited Detail: 89.3%
Redelineation: 6.3%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03010104 17 63% Detailed: 19.9%
Limited Detail: 73.3%
Redelineation: 6.8%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03010106 17 43% Detailed: 32%
Limited Detail: 52.6%
Redelineation: 15.4%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03010107 17 51% Detailed: 28.1%
Limited Detail: 64.8%
Redelineation: 6.5%
Approximate: 0.6%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03010203 16 51% Detailed: 2.6%
Limited Detail: 92.4%
Redelineation: 5%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03010204 16 68% Detailed: 16.2%
Limited Detail: 83.8%
Redelineation: 0%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03010205 15 10% Detailed: 24.8%
Limited Detail: 72.6%
Redelineation: 2.6%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03020101 17 55% Detailed: 44%
Limited Detail: 55.6%
Redelineation: 0.4%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03020102 18 46% Detailed: 8.8%
Limited Detail: 82.8%
Redelineation: 8.4%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 8
HUC 8
Age
(yrs)
Scale
(%) Level of Detail (%)
Modeling
Platform
Availability
Flood
Hazards
Modeled
Future
Conditions
(%)
03020103 17 50% Detailed: 47.5%
Limited Detail: 51.5%
Redelineation: 0.8%
Approximate: 0.2%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03020104 13 13% Detailed: 70.3%
Limited Detail: 27.8%
Redelineation: 1.9%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03020201 13 73% Detailed: 65.1%
Limited Detail: 34.4%
Redelineation: 0.5%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
16%
03020202 16 42% Detailed: 65.1%
Limited Detail: 33.6%
Redelineation: 1.3%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03020203 16 51% Detailed: 55.6%
Limited Detail: 44.4%
Redelineation: 0%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0.09%
03020204 17 22% Detailed: 19.7%
Limited Detail: 78.3%
Redelineation: 2%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03020301 21 22% Detailed: 6.8%
Limited Detail: 87.7%
Redelineation: 5.5%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03020302 19 40% Detailed: 30.9%
Limited Detail: 56.5%
Redelineation: 12.5%
Approximate: 0.1%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03030002 14 91% Detailed: 32.4%
Limited Detail: 52.2%
Redelineation: 15.4%
Approximate: 0%
Open: HEC-
RAS, SWMM
10%, 4%,
2%, 1%,
0.2%
4.7%
03030003 18 74% Detailed: 12.2%
Limited Detail: 76.3%
Redelineation: 10.5%
Approximate: 1%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 9
HUC 8
Age
(yrs)
Scale
(%) Level of Detail (%)
Modeling
Platform
Availability
Flood
Hazards
Modeled
Future
Conditions
(%)
03030004 18 65% Detailed: 13.6%
Limited Detail: 62.6%
Redelineation: 18.3%
Approximate: 5.5%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03030005 17 33% Detailed: 13.6%
Limited Detail: 62.6%
Redelineation: 18.3%
Approximate: 5.5%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03030006 16 48% Detailed: 18%
Limited Detail: 80.8%
Redelineation: 1.2%
Approximate: 0%
Open: HEC-
RAS.
Proprietary:
ICPR,
XPSWMM
10%, 4%,
2%, 1%,
0.2%
0%
03030007 18 50% Detailed: 18%
Limited Detail: 76.3%
Redelineation: 4.7%
Approximate: 1%
Open: HEC-
RAS.
Proprietary:
XPSWMM
10%, 4%,
2%, 1%,
0.2%
.9%
03040101 16 63% Detailed: 7.9%
Limited Detail: 76.1%
Redelineation: 16%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03040102 16 61% Detailed: 10.2%
Limited Detail: 85.7%
Redelineation: 4.1%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03040103 16 63% Detailed: 13%
Limited Detail: 60%
Redelineation: 27%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03040104 16 62% Detailed: 9.8%
Limited Detail: 86.7%
Redelineation: 3.3%
Approximate: 0.2%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03040105 14 84% Detailed: 42.9%
Limited Detail: 51.5%
Redelineation: 5.6%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
10.4%
03040201 16 57% Detailed: 9.4%
Limited Detail: 86.9%
Redelineation: 3.7%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 10
HUC 8
Age
(yrs)
Scale
(%) Level of Detail (%)
Modeling
Platform
Availability
Flood
Hazards
Modeled
Future
Conditions
(%)
03040202 16 94% Detailed: 0%
Limited Detail: 100%
Redelineation: 0%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03040203 18 52% Detailed: 23.2%
Limited Detail: 75.1%
Redelineation: 1.7%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03040204 20 63% Detailed: 9.5%
Limited Detail: 90.5%
Redelineation: 0%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03040206 17 40% Detailed: 25.8%
Limited Detail: 72.9%
Redelineation: 0%
Approximate: 1.3%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03040208 20 37% Detailed: 51.1%
Limited Detail: 45.7%
Redelineation: 0%
Approximate: 3.2%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03050101 16 65% Detailed: 19.8%
Limited Detail: 60.2%
Redelineation: 20%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
3.4%
03050102 17 70% Detailed: 12.8%
Limited Detail: 57.6%
Redelineation: 29.6%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
03050103 13 89% Detailed: 63.6%
Limited Detail: 34%
Redelineation: 2.4%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
47%
3050105 16 61% Detailed: 12.6%
Limited Detail: 84.4%
Redelineation: 0%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
3060101 15 61% Detailed: 9.3%
Limited Detail: 90.7%
Redelineation: 0%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 11
HUC 8
Age
(yrs)
Scale
(%) Level of Detail (%)
Modeling
Platform
Availability
Flood
Hazards
Modeled
Future
Conditions
(%)
3060102 15 28% Detailed: 0%
Limited Detail: 94.3%
Redelineation: 0%
Approximate: 5.7%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
5050001 15 51% Detailed: 25.6%
Limited Detail: 43%
Redelineation: 31.4%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
6010103 16 41% Detailed: 44.5%
Limited Detail: 44%
Redelineation: 11.5%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
6010105 16 48% Detailed: 20.7%
Limited Detail: 51.4%
Redelineation: 26%
Approximate: 1.9
Open: HEC-
RAS, HEC-2
10%, 4%,
2%, 1%,
0.2%
0%
6010106 15 27% Detailed: 46.3%
Limited Detail: 46.4%
Redelineation: 6.4%
Approximate: 0.9%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
6010108 15 43% Detailed: 9.3%
Limited Detail: 64.3%
Redelineation: 24.4%
Approximate: 2%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
6010202 14 36% Detailed: 17.7%
Limited Detail: 77.7%
Redelineation: 0%
Approximate: 4.6%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
6010203 15 35% Detailed: 18.4%
Limited Detail: 64%
Redelineation: 17.1%
Approximate: 0.5%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
6010204 12 66% Detailed: 6.3%
Limited Detail: 62.6%
Redelineation: 0%
Approximate: 31.1%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
6020002 16 39% Detailed: 13.9%
Limited Detail: 76.5%
Redelineation: 9.6%
Approximate: 0%
Open: HEC-
RAS
10%, 4%,
2%, 1%,
0.2%
0%
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 12
HUC 8
Age
(yrs)
Scale
(%) Level of Detail (%)
Modeling
Platform
Availability
Flood
Hazards
Modeled
Future
Conditions
(%)
Total
Average
16 52% Detailed: 23.8%
Limited Detail: 67.2%
Redelineation: 7.7%
Approximate: 1.3%
N/A N/A 3.3%

Table 4 presents gaps identified in the NCFMP regulatory modeling dataset.
Table 4: NCFMP Regulatory Modeling Data Gaps
Identified Gaps
Age • The average age of the currently effective regulatory models across the state is 16
years. Many models are therefore based on outdated data (LiDAR, gauge records,
hydraulic structures, etc.). Many models have already been updated and are
either preliminary or planned preliminary and subject to change during their
regulatory appeal period. These updated models may still be used as the best
available data . Additional coordination with the NCFMP and use of the North
Carolina Coordinated Needs Management Strategy Database would provide
insight on the extent of completed studies not yet effective that could be available
for use in the Blueprint.
Scale
(Spatial Extent)
• The average coverage of effective regulatory studies over streams draining at
least ½ sq mile is 52%.
Level of Detail • Many studies are based on redelineation (typically dated HEC-2 models),
approximate (model availability uncertain), or limited detail (no field survey).
• NCFMP has performed “Model Upgrades” to add missing profiles to models for
purposes of multi-return water surface elevation raster datasets needed for multi-
return flood risk assessments. These models are only available through specific
request to the NCFMP.
Modeling Platform
Availability
• None
Flood Hazards
Modeled
• Not all models have all noted frequency events. Approximate and Limited
Detailed studies are limited to the 1% annual chance event. Older Detail studies
do not include the 4% annual chance event. The 1%+ (statistical upper limit of 1%
annual chance event) could be added for awareness and conservatism.
Future Conditions • Only 3.3% of effective regulatory study mileage across the state includes
consideration for future conditions.

North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 13
NCFMP’s regulatory modeling dataset is one of the most complete statewide datasets of its kind in the
country. This modeling, where available, should be considered as a starting point for additional H&H
modeling efforts identified as part of the Blueprint. The primary gaps noted for age, scale, level of
detail, flood hazards modeled, and future conditions are all being incrementally addressed as annual
funding cycles from FEMA and the North Carolina (NC) Cooperating Technical Partners program allow.
2.2 North Carolina Emergency Management Base Level Modeling
During Hurricanes Matthew and Florence, the NCFMP located within NCEM, identified a large number
of buildings impacted by flooding that were not located in regulatory study areas. In 2020, NCFMP
undertook a new effort to use rain-on-grid 2D modeling with HEC-RAS to model entire HUC 10 basins.
The goal of this effort was to produce advisory flood hazard information in previously unmapped
areas to supplement the existing regulatory data. Unlike the regulatory modeling, which primarily
uses Detailed and Limited Detail study approaches as explained in the previous section, the advisory
modeling was performed using base-level methods. Base-level models are considered approximate
and use a relatively coarse grid cell (100-200 feet in most areas). The models do not include hydraulic
structures (bridges, culverts). In addition, flows along mainstems in non-headwater basins use
baseflow only and do not carry the modeled flow from the upstream basin. The NCFMP developed an
enterprise database to house the H&H modeling results and mapping products made available in the
Advisory Mapping Viewer. Table 5 provides summary information for the NCFMP advisory modeling
dataset.
Table 5: NCEM Base Level Modeling Dataset Information
NCEM Base Level Modeling
Source of Information North Carolina Emergency Management – Floodplain Mapping Program
Link to Online Data https://flood.nc.gov/advisoryflood/
Data Owner State of North Carolina
Date Created 2022
Date of Access February 2023
Frequency of Updates Annual funding for cyclical updates throughout the state
Update Needed No

North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 14
Table 6 below describes the criteria used to perform the gap analysis . The actual criteria are
presented in Table 7.
Table 6: NCEM Base Level Modeling Gap Analysis Criteria Description
Criteria Description
Age The average age of model is provided.
Scale (Spatial Extent) The total miles of advisory study within each HUC 8 is added to the regulatory
miles and compared to the total estimated miles of streams draining ½ square
mile (considered to be a minimum drainage area feasible for a regulatory H&H
model). Basins with no advisory mapping available receive a “0”. Note the %
may be greater than 100 if there are more advisory miles identified than
estimated miles of streams draining ½ square mile.
Level of Detail The study type – Base Level
Modeling Platform
Availability
Open source or proprietary modeling software.
Flood Hazards
Modeled
Flood recurrence interval events analyzed.
Future Conditions The % of miles with future conditions compared to the total estimated miles of
streams draining ½ square mile. For purposes of this dataset, future conditions
are increasing the 1% annual chance rainfall by 10, 20, and 30% to simulate
potential future climate change conditions .

The requested gap analysis criteria were analyzed by summarizing the advisory H&H model
information available in the NCFMP enterprise database by HUC 8. Figure 4 below presents the
advisory modeling dataset’s scale (coverage) summarized by HUC 8. Table 7 summarizes the gap
analysis criteria by HUC 8.
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 15

Figure 4: NCEM Base Level Modeling Scale (Coverage)
Table 7: NCEM Base Level Modeling Gap Analysis Criteria
HUC 8
Age
(yrs)
Scale
(%)
Level of
Detail
Modeling
Platform
Availability Flood Hazards Modeled
Future
Conditions
3010102 NA 0% NA NA NA 0%
3010103 NA 0% NA NA NA 0%
3010104 NA 0% NA NA NA 0%
3010106 NA 0% NA NA NA 0%
3010107 2 150% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
150%
3010203 2 140% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
140%
3010204 NA 0% NA NA NA 0%
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 16
HUC 8
Age
(yrs)
Scale
(%)
Level of
Detail
Modeling
Platform
Availability Flood Hazards Modeled
Future
Conditions
3010205 2 17% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
17%
3020101 2 121% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
121%
3020102 2 118% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
118%
3020103 2 191% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
191%
3020104 2 13% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
13%
3020201 2 117% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
117%
3020202 2 163% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
163%
3020203 2 239% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
239%
3020204 2 47% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
47%
3020301 NA 0% NA NA NA 0%
3020302 NA 0% NA NA NA 0%
3030002 NA 0% NA NA NA 0%
3030003 NA 0% NA NA NA 0%
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 17
HUC 8
Age
(yrs)
Scale
(%)
Level of
Detail
Modeling
Platform
Availability Flood Hazards Modeled
Future
Conditions
3030004 2 231% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
231%
3030005 2 62% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
62%
3030006 2 164% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
164%
3030007 2 125% Base Level Open: HEC-
RAS
20-, 10-, 4-, 2-, 1-, 1+, 0.5-, 0.2-,
0.1%, and 1% with 10-, 20-, and
30% increases in rainfall
125%
3040101 NA 0% NA NA NA 0%
3040102 NA 0% NA NA NA 0%
3040103 NA 0% NA NA NA 0%
3040104 NA 0% NA NA NA 0%
3040105 NA 0% NA NA NA 0%
Table 8 presents gaps identified in the NCEM base level modeling dataset.
Table 8: NCEM Base Level Modeling Data Gaps
Identified Gaps
Age • None currently, however, a maintenance cycle needs to be established to keep
current.
Scale
(Spatial Extent)
• Where advisory mapping exists, it provides particularly good coverage of flood
hazards up to and beyond ½ sq mile in many locations. The dataset is not yet
statewide although additional studies are ongoing.
Level of Detail • The models are base-level. No field survey of hydraulic structures.
• Downstream basins only include baseflow from upstream basins so mainstem
flooding can be unconservative. However, mainstem flooding is covered by
regulatory models in separate dataset.
Modeling Platform
Availability
• Modeling software is open source, but models are not readily available for
download. Coordination with NCEM needed.
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 18
Identified Gaps
Flood Hazards
Modeled
• None
Future Conditions • Climate change runs consider increases to 1% rainfall depth only. Future land use
depicting more development and increased runoff potential not analyzed.
North Carolina’s initial efforts at developing an advisory modeling dataset has provided awareness of
the capability of large-scale two-dimensional base-level modeling to improve flood hazard and risk
identification for flooding sources not covered by regulatory modeling. The primary gap in the dataset
at this time is the extent/scale across the state. Only a portion of the state has been modeled using
this approach. Once this dataset’s extent can be expanded to cover the state, it in addition to the
regulatory modeling will likely provide the necessary foundation to develop and expand H&H
modeling needs as identified as part of the Blueprint.
2.3 North Carolina Emergency Management Dam Breach Modeling
North Carolina Dam Safety maintains a hazard classification system including; “Class A (Low)” –
Failure may damage uninhabited low value non-residential buildings, agricultural land, or low volume
roads, “Class B (Intermediate)” - failure may damage highways or secondary railroads, cause
interruption of use or service of public utilities, cause minor damage to isolated homes, or cause
minor damage to commercial and industrial buildings, and “Class C (High)” - failure will likely cause
loss of life or serious damage to homes, industrial and commercial buildings, important public
utilities, primary highways, or major railroads. Following Hurricane Matthew in 2016, North Carolina
Emergency Management (NCEM) piloted base-level 2D hydraulic modeling of dam breaches for a
select group of dams. This pilot was later followed up by a much larger study intended to model the
majority of high and intermediate hazard dams across the state. Results of these models are used in
the State Emergency Response Application and DamWatch, a third-party remote monitoring
application for dams. Table 9 provides summary information for the NCEM dam breach modeling
dataset. Figure 5 below provides the spatial location of dams analyzed for this dataset.
Table 9: NCEM Dam Breach Modeling Dataset Information
NCEM Dam Breach Modeling
Source of Information North Carolina Emergency Management
Link to Online Data https://sera.nc.gov/SERA/*
Data Owner State of North Carolina
Date Created 2017
Date of Access February 2023
Frequency of Updates Uncertain
Update Needed No
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 19
NCEM Dam Breach Modeling
* Site is access restricted

Table 10 below summarizes the criteria used to perform the gap analysis.
Table 10: NCEM Dam Breach Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age 2-6 years
Scale (Spatial
Extent)
The dataset is statewide and includes dam breach modeling and inundation
mapping for over 1,500 dams out of the approximately 6,100 dams in the
statewide dam inventory (~25%). However, the majority of the unstudied dams
are low hazard and not anticipated to have significant impacts if breached.
Level of Detail Base-level/approximate. Single breach scenario modeled. No field survey or
modeling of hydraulic structures (bridges/culverts).
Modeling Platform
Availability
Open source (HEC-RAS 2D)
Flood Hazards
Modeled
Brim-up dam breach with 1% annual chance baseflow
Future Conditions None considered

Figure 5: NCEM Dam Breach Modeling Spatial Extent
Table 11 presents gaps identified in the NCEM dam breach modeling dataset.
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 20
Table 11: NCEM Dam Breach Modeling Data Gaps
Identified Gaps
Age • Existing analyses sufficient for studied dams. New or significantly
redesigned significant or high hazard dams would need analyzed.
Scale (Spatial Extent) • None
Level of Detail • Models are base-level and do not include field survey or modeling of
hydraulic structures.
Modeling Platform
Availability
• Modeling software is open source, but models are not readily available for
download. Coordination with NCEM needed.
Flood Hazards Modeled • Only a single breach scenario modeled. Additional analyses including
Probable Maximum Flood iterations could be added but would require
change in methodology.
Future Conditions • Increases in future rainfall and/or development could be considered but
would require a change in methodology.

NCEM’s dam breach modeling dataset provides significant awareness of dam breach flood hazards for
intermediate and high hazard dams (those most likely to cause significant impacts in the event of a
failure). Depending on how dam breach flooding is accounted for in the Blueprint, the models provide
a particularly good initial cut at identifying the hazard and impacts for a single hypothetical event. The
models may be improved with additional data collection and breach scenarios under different
conditions.
2.4 North Carolina Dam Safety and NCEM Dam Overtopping
Modeling
In coordination with North Carolina Dam Safety, NCEM expanded upon an effort to develop dam
overtopping modeling for a select group of dams, primarily in the western part of the state. Using the
HEC-HMS hydrologic model, a series of annual chance recurrence interval events were analyzed to
determine what event (if any) would overtop the dam. Results of these models are used in DamWatch,
a third-party remote monitoring application for dams, to set alert thresholds based on available
rainfall data sources from the National Weather Service (NWS).
Prior to this effort, NC Dam Safety had performed similar analyses in the Cape Fear and Neuse River
basins. In total an estimated 555 dams were analyzed to determine overtopping events with HEC-HMS
hydrologic models. Table 12 provides summary information for the NC Dam Safety and NCEM dam
overtopping modeling dataset. Figure 6 below provides the spatial location of dams analyzed for this
dataset.
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 21
Table 12: NCEM Dam Overtopping Modeling Dataset Information
NCEM Dam Overtopping Modeling
Source of Information North Carolina Emergency Management
Link to Online Data https://ncdps.damwatch.us/main/admin-login.html*
Data Owner State of North Carolina
Date Created 2020
Date of Access February 2023
Frequency of Updates Uncertain
Update Needed No
* Site is access restricted
Table 13 below summarizes the criteria used to perform the gap analysis.
Table 13: NCEM Dam Overtopping Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age 3-5 years
Scale (Spatial Extent) The dataset is statewide but limited to only 530 dams out of the
approximately 6,100 dams in the statewide dam inventory (~9%). Analyses
heavily weighted towards the western part of the state.
Level of Detail Limited. Existing datasets used for determination of critical dam and reservoir
characteristics (surface area, volume, height, etc.). No site-specific field survey
collected.
Modeling Platform
Availability
Open source (HEC-HMS)
Flood Hazards Modeled 4-, 2-, 1-, 0.5-, 0.2-, 0.1% annual chance
Future Conditions None considered

North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 22

Figure 6: NCEM Dam Overtopping Modeling Spatial Extent

Table 14 presents gaps identified in the NCEM dam overtopping modeling dataset.
Table 14: NCEM Dam Overtopping Modeling Data Gaps
Identified Gaps
Age • Existing analyses sufficient for studied dams. New or significantly
redesigned dams meeting analysis criteria would need analyzed.
Scale (Spatial Extent) • Only a relatively small % of dams are included. Many additional high and
significant hazard dams could be analyzed.
Level of Detail • Models are base-level using the best available remote data or engineering
plans/drawings. Additional/updated site-specific data could be collected
to improve analyses.
• Hydrologic parameters developed with simplified procedures and single-
basin approach.
Modeling Platform
Availability
• Modeling software is open source, but models are not readily available for
download. Coordination with NCEM needed.
Flood Hazards Modeled • None
Future Conditions • Increases in future rainfall and/or development could be considered but
would require a change in methodology.

In addition to its intended purpose to support the DamWatch monitoring application, NCEM’s dam
overtopping modeling provides a potentially valuable resource for accounting for flood storage
volume available in basins across the state. The available stage/storage/discharge data in the models
for the dams analyzed can be input into other more large-scale hydrologic models to better represent
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 23
flood storage and attenuation available within the basin being studied. The largest gap identified is
scale/extent of the completed modeling. Many other dams across the state could be analyzed.
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 24
2.5 North Carolina Emergency Management Basin Mitigation
Modeling
Following Hurricanes Matthew (2016) and Florence (2018) elevated attention was given to flood-prone
areas throughout eastern North Carolina. NCEM, in partnership with North Carolina Department of
Transportation (NCDOT) began funding flood mitigation studies to identify primary sources of
flooding and evaluate potential mitigation strategies to reduce flood impacts. These studies included
development and calibration of watershed-scale hydrologic models and use of existing hydraulic
models to support risk assessments used in benefit/cost analyses for proposed mitigation strategies.
Table 15 provides summary information for the NCEM basin mitigation modeling dataset. Figure 7
below provides the spatial location of basins analyzed by NCEM to date.
Table 15: NCEM Basin Mitigation Modeling Dataset Information
NCEM Basin Mitigation Modeling
Source of Information North Carolina Emergency Management
Link to Online Data https://www.rebuild.nc.gov/resiliency/river-basin-studies
Data Owner State of North Carolina
Date Created 2018
Date of Access February 2023
Frequency of Updates Uncertain
Update Needed No

Table 16 below summarizes the criteria used to perform the gap analysis.
Table 16: NCEM Basin Mitigation Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age 2-5 years
Scale (Spatial Extent) To date, the Tar, Neuse, Lumber, and Cape Fear watersheds have been
studied (along with the Cashie River Basin within the Roanoke watershed),
representing approximately 46% of the state. Within these watersheds, the
studies focused on the mainstem flooding sources (the primary river that
drains the total area of the watershed) and most significant tributaries.
Level of Detail Limited. Watershed hydrologic models are coarse due to size. Existing
regulatory hydraulic models used with limited adjustments.
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 25
Gap Analysis Criteria
Modeling Platform
Availability
Open source (HEC-HMS, HEC-RAS)
Flood Hazards Modeled 10%, 4%, 2%, 1%, 0.2%, 0.1% annual chance
Future Conditions None considered

Figure 7: Completed NCEM River Basin Studies
Table 17 presents gaps identified in the NCEM basin mitigation modeling dataset.
Table 17: NCEM Basin Mitigation Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • Not all basins within the state have been studied.
• Studies focused only on the mainstem flooding sources and significant
tributaries. Flooding impacts potentially receptive to mitigation strategies
may be present on smaller tributaries adjacent to dense development.
Level of Detail • None given scope of study.
• More detailed modeling could be performed for smaller areas of particular
interest.
Modeling Platform
Availability
• Modeling software is open source, but models are not readily available for
download. Coordination with NCEM needed.
Flood Hazards Modeled • None
Future Conditions • Increases in future rainfall and/or development could be considered in
modeling.
North Carolina Flood Resiliency Blueprint

Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 26

NCEM’s basin mitigation modeling provides valuable high-level hydrologic modeling that has been
calibrated to significant flooding events experienced within the watershed. These models were used
to analyze potential flood mitigation projects and could be used to analyze additional alternatives as
they are identified. The models can be manipulated to add more detail in areas of interest or to model
additional flooding scenarios including various future conditions. The largest gap identified is
scale/extent as not all basins in the state have been studied .
2.6 North Carolina Dam Safety Emergency Action Plan Breach
Modeling
The Coal Ash Management Act of 2014 requires that all owners of High (Class C) and Intermediate
(Class B) hazard dams in North Carolina develop an Emergency Action Plan. The plan must include
downstream inundation maps that are supported by and developed using engineering computer
models. NC Dam Safety reviews and inventories these models for potential use/reference during
emergency events. Table 18 provides summary information for the North Carolina Dam Safety
emergency action plan breach modeling dataset.
Table 18: NC Dam Safety Emergency Action Plan Breach Modeling Dataset Information
NC Dam Safety Breach Modeling
Source of Information North Carolina Emergency Management
Link to Online Data https://deq.nc.gov/about/divisions/energy-mineral-and-land-resources/dam-
safety
Data Owner Varies – Private landowners, HOAs, Municipalities, State Agencies, Federal
Agencies
Date Created Requirement for all high and intermediate hazard dams to have an Emergency
Action Plan (EAP) with dam breach modeling began in 2014 with the due date
of December 31, 2015. Annual updates to EAP (including insurance that dam
breach modeling/mapping is updated) is required.
Date of Access February 2023
Frequency of Updates Uncertain
Update Needed Annual reviews, modeling may not require update

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Table 19 below summarizes the criteria used to perform the gap analysis.
Table 19: NC Dam Safety Emergency Action Plan Breach Modeling Gap Analysis
Criteria Summary
Gap Analysis Criteria
Age 1-9 years
Scale (Spatial Extent) Statewide
Level of Detail Varies. High hazard dams, in particular, typically require high level of detail
Modeling Platform
Availability
Varies. Many are open source such as HEC-RAS however some may be
proprietary such as FLO-2D, GeoHECRAS, MIKE 11/21.
Flood Hazards Modeled Sunny-day and spillway design flood breach scenarios
Future Conditions None considered

Table 20 presents gaps identified in the North Carolina Dam Safety emergency action plan breach
modeling dataset.
Table 20: NC Dam Safety Emergency Action Plan Breach Modeling Data Gaps
Identified Gaps
Age None
Scale (Spatial Extent) None
Level of Detail Level of detail may vary significantly as the modeling is not performed in a
consistent manner.
Modeling Platform
Availability
Modeling software used may vary significantly and include the use of
proprietary models. Models are not readily available for download and may
not be public information. Coordination with Dam Safety needed.
Flood Hazards Modeled None
Future Conditions Increases in future rainfall and/or development could be considered.

NC Dam Safety’s Emergency Action Plan breach modeling could provide value to the Blueprint
depending on dam breach flooding’s place in the program. The modeling available from NC Dam
Safety is likely more detailed than the base-level dam breach modeling performed by NCEM. The
modeling and data consistency may vary significantly and pose complications in its use. If available,
dam breach modeling for the largest dams across the state in this dataset may be valuable to identify
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large areas of potential impacts during the most unlikely and conservative of events, the Probable
Maximum Flood.
2.7 North Carolina Department of Transportation Hydraulic Design
Modeling
NCDOT is responsible for management, maintenance, and replacement of a majority of roads and
bridges across the state. There are some roads and bridges that are owned by counties or cites.
Whenever NCDOT projects cross streams, a H&H modeling effort is undertaken to support the design
of the new road and/or bridge. The models typically include multiple iterations of potential storm
events of varying probabilities of occurrence (also known as design profiles) and if crossing a
regulatory study stream, the effective regulatory study’s modeled flood events as well. Projects
crossing regulatory study streams also require a specific version of the model for a State Floodplain
Compliance (SFC) review as part of a memorandum of agreement with the NCFMP. Since 2012 well
over 1,000 SFC models have been submitted and reviewed for NCDOT projects. Table 21 provides
summary information for the NCDOT hydraulic design modeling dataset.
Table 21: NCDOT Hydraulic Design Modeling Dataset Information
NCDOT Hydraulic Design Modeling
Source of Information North Carolina Department of Transportation
Link to Online Data https://connect.ncdot.gov/resources/hydro/Pages/FEMA-Interagency-
Design.aspx
Data Owner NCDOT
Date Created Varies
Date of Access February 2023
Frequency of Updates None – modeling performed per project during design phase
Update Needed No

Table 22 below summarizes the criteria used to perform the gap analysis.
Table 22: NCDOT Hydraulic Design Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age Varies
Scale (Spatial Extent) Statewide.
Level of Detail High
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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 29
Gap Analysis Criteria
Modeling Platform
Availability
Varies. Design models are typically open source (HEC-RAS) but may also be
proprietary. Associated SFC models are in format consistent with the effective
regulatory model.
Flood Hazards Modeled Design specific. SFC model versions include profiles from effective regulatory
model: 10-, 4-, 2-, 1-, 0.2% annual chance events.
Future Conditions Design specific. SFC model versions will include future conditions profiles if
the effective model had them.

Table 23 presents gaps identified in the NCDOT hydraulic design modeling dataset.
Table 23: NCDOT Hydraulic Design Modeling Data Gaps
Identified Gaps
Age None
Scale (Spatial Extent) Each model may have limited extent only covering the reach of the stream
affected by the project.
Level of Detail None
Modeling Platform
Availability
Modeling software used may vary significantly and include the use of
proprietary models. Models are not readily available for download.
Coordination with NCDOT needed.
Flood Hazards Modeled None
Future Conditions Increases in future rainfall and/or development could be considered.

NCDOT’s hydraulic design modeling provides a valuable dataset that can be used to update NCFMP
regulatory and/or advisory modeling in potentially a timelier manner than the typical flood study
maintenance updates may allow. This improves the accuracy of the modeling by ensuring the
hydraulic structures (bridges/culverts) in the model reflect current conditions with a high level of
detail.
2.8 North Carolina Department of Transportation Resiliency
Studies
NCDOT adopted an official resilience policy (NCDOT Policy F.35.0102) in September of 2021. As part of
NCDOT’s mission to create a more resilient transportation network, they have published and will
continue to publish studies and reports assessing the state’s current level of resilience, future needs,
and upcoming projects. This work is also being done in accordance with Executive Order 80, which
addresses climate change facing the state. NCDOT is currently developing climate adaptation
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strategies into planning and design. They consider sea level rise, rainfall, and extreme events when
designing critical infrastructure. NCDOT has performed a number of resiliency and vulnerability
studies for certain strategic highway corridors including US-74, NC-210, I-95, and I-40/US-17 that have
incorporated sea level rise, heat, future rainfall, and extreme events. Portions of these studies have
included both 1D and 2D (including rain on grid) H&H modeling to better understand current and
future flood risk. Table 24 provides summary information for the NCDOT transportation resiliency
modeling dataset.
Table 24: NCDOT Transportation Resiliency Modeling Dataset Information
NCDOT Transportation Resiliency Studies
Source of Information North Carolina Department of Transportation
Link to Online Data https://www.ncdot.gov/initiatives-policies/Transportation/transportation-
resilience/Pages/default.aspx
Data Owner NCDOT
Date Created Varies
Date of Access February 2023
Frequency of Updates Uncertain
Update Needed No

Table 25 below summarizes the criteria used to perform the gap analysis.
Table 25: NCDOT Transportation Resiliency Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age Varies
Scale (Spatial Extent) Statewide, focused on strategic highway corridors with known flood
vulnerabilities.
Level of Detail High
Modeling Platform
Availability
Typically, open source (predominantly HEC-RAS), although proprietary
models may be used. SRH2D is a preference of the Federal Highway
Administration and although it is technically open source, often SMS
(proprietary software developed by Aquaveo) is considered necessary for
model development.
Flood Hazards Modeled Uncertain
Future Conditions Yes, compliant with Executive Order 80 to address climate change.
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Table 26 presents gaps identified in the NCDOT hydraulic design modeling dataset.
Table 26: NCDOT Transportation Resiliency Modeling Data Gaps
Identified Gaps
Age None
Scale (Spatial Extent) The current extent of modeling is unknown. Additional data collection and
coordination needed.
Level of Detail None
Modeling Platform
Availability
None
Flood Hazards Modeled Uncertain. Additional data collection and coordination needed.
Future Conditions None

NCDOT’s transportation resiliency modeling, although limited in extent, provides valuable insight and
examples of how to integrate future conditions into H&H modeling to develop more flood resilient
alternatives in areas at risk of flooding.
2.9 North Carolina Department of Environmental Quality Basin-
wide Hydrologic Modeling
With a goal to improve water resources planning throughout the state, in 2010 the North Carolina
General Assembly directed the North Carolina Department of Environmental Quality (NCDEQ) to
develop basin-wide hydrologic models for all 17 river basins in the state. NCDEQ uses these models to
evaluate potential impacts of proposed projects that affect water withdrawals or inter-basin transfers.
The models are useful for growth planning and drought evaluations. Table 27 provides summary
information for the NCDEQ basin-wide hydrologic modeling dataset. Figure 8 below provides the
current status of basin-wide hydrologic modeling performed by NCDEQ.
Table 27: NCDEQ Basin-wide Hydrologic Modeling Dataset Information
NCDEQ Basin-wide Hydrologic Modeling
Source of Information North Carolina Department of Environmental Quality
Link to Online Data https://deq.nc.gov/about/divisions/water-resources/water-planning/modeling-
assessment/basinwide-hydrologic-modeling
Data Owner NCDEQ
Date Created Varies
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NCDEQ Basin-wide Hydrologic Modeling
Date of Access February 2023
Frequency of Updates Uncertain
Update Needed No

Figure 8: NCDEQ Basin-wide Hydrologic Modeling Status
Table 28 below summarizes the criteria used to perform the gap analysis.
Table 28: NCDEQ Basin-wide Hydrologic Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age Varies
Scale (Spatial Extent) Statewide
Level of Detail Uncertain
Modeling Platform
Availability
Uncertain. OASIS model is proprietary.
Flood Hazards Modeled Uncertain, if any. Model purpose is water use, not flooding.
Future Conditions Uncertain

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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 33
Table 29 presents gaps identified in the NCDEQ basin-wide hydrologic modeling dataset.
Table 29: NCDEQ Basin-wide Hydrologic Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • None
Level of Detail • Additional data collection, coordination needed.
Modeling Platform
Availability
• Uncertain. The OASIS model is proprietary. Additional data collection,
coordination needed.
Flood Hazards Modeled • Uncertain. Additional data collection and coordination needed.
Future Conditions • Uncertain. Additional data collection and coordination needed.

NCDEQ’s basin-wide hydrologic modeling is performed with a focus on water supply and long-term
planning, not flooding . Anticipated usefulness for the Blueprint is uncertain but expected to be
minimal. As noted in the NCDEQ’s documentation, “Modeling the Cape Fear and Neuse River Basins
Operations with OASIS” by Hydrologics (dated November 2013), “OASIS is a generalized type of mass
balance model used mainly in evaluating planning and management alternatives. It is not intended
for use in hydraulic routing nor flood management, although it can be linked to other models for
those purposes.” As the OASIS model is proprietary, its availability for use in support of the Blueprint
is uncertain.
2.10 North Carolina Department of Environmental Quality Water
Quality Modeling
The NCDEQ Division of Water Resources uses water quality models for a variety of reasons including
evaluation of waste-water discharges, analysis of pollutant load and reduction to water bodies, and
support of nutrient management strategies or total maximum daily load allocations. Table 30
provides summary information for the NCDEQ water quality modeling dataset.
Table 30: NCDEQ Water Quality Modeling Dataset Information
NCDEQ Water Quality Modeling
Source of Information North Carolina Department of Environmental Quality
Link to Online Data https://deq.nc.gov/about/divisions/water-resources/planning/modeling-
assessment/water-quality-monitoring
Data Owner NCDEQ
Date Created Varies
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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 34
NCDEQ Water Quality Modeling
Date of Access February 2023
Frequency of Updates Uncertain
Update Needed Uncertain

Table 31 below summarizes the criteria used to perform the gap analysis.
Table 31: NCDEQ Water Quality Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age Varies
Scale (Spatial Extent) Statewide
Level of Detail Varies
Modeling Platform
Availability
Uncertain. Models include WARMF, EFDC, GWLF, SWAT, and HSPF.
Flood Hazards Modeled Uncertain, if any. Model purpose is water quality, not flooding.
Future Conditions Uncertain

Table 32 presents gaps identified in the NCDEQ water quality modeling dataset.
Table 32: NCDEQ Water Quality Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • None
Level of Detail • Additional data collection, coordination needed.
Modeling Platform
Availability
• Uncertain if models are open source or proprietary. Additional data
collection and coordination needed.
Flood Hazards Modeled • Uncertain. Additional data collection and coordination needed.
Future Conditions • Uncertain. Additional data collection and coordination needed.

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NCDEQ’s water quality modeling is not focused on quantity or flooding. The anticipated usefulness for
the Blueprint is minimal.
2.11 North Carolina Floodplain Mapping Regulatory Coastal
Modeling
As part of the North Carolina Floodplain Mapping Program introduced earlier in this section, coastal
modeling has been performed using Advanced Circulation (ADCIRC) for storm surge and Simulating
Waves Nearshore (SWAN) for waves to identify coastal flood hazards. Results of the coastal modeling
are housed in the statewide enterprise FLOOD database along with the riverine modeling and can be
viewed on the FRIS website.
Table 33 provides summary information for the NCFMP Regulatory Coastal modeling.
Table 33: NCFMP Regulatory Coastal Modeling Dataset Information
NCFMP Regulatory Coastal Modeling
Source of Information North Carolina Emergency Management – Floodplain Mapping Program
Link to Online Data https://fris.nc.gov/fris/Home.aspx?ST=NC
Data Owner State of North Carolina
Date Created 2010-2016
Date of Access August 2023
Frequency of Updates Annual funding for cyclical updates throughout the state based on age of
existing study, need, and available data.
Update Needed Yes – Regular updates necessary to maintain reliable products

Table 34 below summarizes the United States Geological Survey (USGS) National Hydrologic Model
(NHM) criteria used to perform the gap analysis.
Table 34: USGS NHM Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age 7 – 13 years
Scale (Spatial Extent) Statewide along the coast
Level of Detail High – Detailed study with defined base flood elevations based on storm surge
and wave impacts. Combined probability of coastal and riverine impacts was
considered in some, but not all areas studied.
Modeling Platform
Availability
ADCIRC and SWAN are both open source; however, SMS (which is proprietary)
is widely considered necessary for model use.
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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 36
Gap Analysis Criteria
Flood Hazards Modeled 10-, 4-, 2-, 1-, 0.2% annual chance
Future Conditions None

Table 35 presents gaps identified in the NCFMP Regulatory Coastal modeling dataset.
Table 35: NCFMP Regulatory Coastal Modeling Data Gaps
Identified Gaps
Age • Modeling dataset is becoming dated and updated base data including new
lidar are now available.
Scale (Spatial Extent) • The coastal study was performed in parts by different contractors with
shared boundary conditions. Some of the modeling may not be fully tied
together.
Level of Detail • Not all of the areas covered by the coastal modeling included combined
probability for coastal/riverine interactions. In addition, combined
probability with pluvial flooding was not considered.
Modeling Platform
Availability
• Coastal modeling methodologies have not changed much and could be
considered for update based on newer technology and data. The coastal
models require supercomputers for computations.
Flood Hazards Modeled • More extreme events such as 0.5- and 0.1% annual chance could be
analyzed.
Future Conditions • Many sea level rise studies have been performed and could be used to
inform potential future conditions. In addition, Weather Research and
Forecasting (WRF) modeling is available to analyze future
climate/atmospheric conditions that may produce more extreme flooding
events.

The NCFMP Regulatory Coastal modeling is a foundational model dataset critical in awareness and
identification of coastal flooding hazards. However, there are several identified gaps that could be
addressed to improve the dataset’s usefulness in resiliency planning efforts. Coastal studies such as
what the NCFMP performed for the North Carolina coast take a significant amount of time and effort.
When used for regulatory and permitting purposes, significant outreach is also necessary.

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3 Other North Carolina Models
3.1 County and Municipality Modeling
Counties and municipalities have a personal stake in high quality, reliable hydrologic and hydraulic
modeling of the flooding sources that impact their residents and jurisdiction . Awareness of the extent
and severity of potential flood impacts provides community officials with valuable information to
ensure development is undertaken responsibly. Communities such as Raleigh, Durham, Charlotte,
Fayetteville, Wilmington, and many others routinely perform and update basin studies to support
planning, development, and design of capital improvement projects. Also of note, the Eastern Band of
Cherokee Indians maintains H&H modeling as well. Table 36 provides summary information for
county and municipality modeling.
Table 36: County and Municipality Modeling Dataset Information
County and Municipality Modeling
Source of Information Varies
Link to Online Data Varies. Examples include: https://raleighnc.gov/projects/pigeon-house-branch-
watershed-study
Data Owner Each community
Date Created Varies
Date of Access NA
Frequency of Updates Varies
Update Needed Yes

Table 37 below summarizes the criteria used to perform the gap analysis.
Table 37: County and Municipality Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age Varies
Scale (Spatial Extent) Varies. Not all communities statewide actively develop modeling and those
that do have different expectations and requirements. Studies are commonly
performed by basin, similar in size to a HUC 12.
Level of Detail Varies. Most are highly detailed to support capital improvement project
design.
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Gap Analysis Criteria
Modeling Platform
Availability
Varies. Different communities require different modeling software, including
some proprietary such as InfoWorks ICM and XPSWMM
Flood Hazards Modeled Varies by community.
Future Conditions Varies by community.

Table 38 presents gaps identified in the NC county and municipality modeling dataset.
Table 38: County and Municipality Modeling Data Gaps
Identified Gaps
Age Additional data collection and coordination with communities is needed.
Scale (Spatial Extent) Additional data collection and coordination with communities is needed.
Level of Detail Additional data collection and coordination with communities is needed.
Modeling Platform
Availability
Additional data collection and coordination with communities is needed.
Flood Hazards Modeled Additional data collection and coordination with communities is needed.
Future Conditions Additional data collection and coordination with communities is needed.

• Although variable across different municipalities, county and municipality modeling is anticipated
to be some of the most detailed modeling available. These models are often used in the design of
capital improvement projects and must therefore contain significant detail. The largest gap for this
dataset is awareness of the availability of the modeling. A significant outreach and coordination
effort may be required to collect and inventory available modeling across the state. If and when the
modeling becomes available, however, it could provide substantial value in evaluating flood
vulnerabilities and potential mitigation alternatives. Examples of additional county/municipality
modeling that may be available through additional outreach activities include: The Town of Cary
requires flood studies to be performed and submitted by developers for non-FEMA regulated
streams.
• Charlotte Mecklenburg is developing detailed 2-D modeling with structures incorporated .
• The City of Fayetteville has and is currently performing detailed 2-D modeling for several
watersheds.
3.2 United States Army Corps of Engineers River Basin Feasibility
Studies
Following the river basin mitigation studies performed by NCEM along the Tar, Neuse, and Lumber
noted above, North Carolina received funding through the 2019 Additional Supplemental
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Appropriations for Disaster Relief (H.R. 2157) for feasibility studies to assess and recommend actions
that reduce flood risk and increase resiliency throughout the Neuse and Tar-Pamlico Basins. The
USACE Wilmington District has released a report for the Neuse Basin while the Pittsburgh District is
currently working on the Tar-Pamlico Basin. The studies use a combination of existing and new H&H
models. Table 39 provides summary information for the USACE river basin feasibility modeling.
Table 39: USACE River Basin Feasibility Modeling Dataset Information
USACE River Basin Feasibility Studies
Source of Information USACE
Link to Online Data https://www.saw.usace.army.mil/Missions/Flood-Risk-Management/Neuse-
River-Basin/
https://www.lrp.usace.army.mil/Missions/Planning-Programs-Project-
Management/Key-Projects/Tar-Pamlico-Feasibility-Study/
Data Owner USACE
Date Created April 2022
Date of Access February 2023
Frequency of Updates Uncertain
Update Needed No

Table 40 below summarizes the criteria used to perform the gap analysis.
Table 40: USACE River Basin Feasibility Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age 1-2 years
Scale (Spatial Extent) Studies performed at a watershed level
Level of Detail Limited. Models are coarse due to size of project area.
Modeling Platform
Availability
Open. HEC-HMS, HEC-RAS
Flood Hazards Modeled 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, 0.2% annual chance
Future Conditions Future conditions are discussed in the report; however, the H&H modeling
does not appear to include any future conditions.

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Subtask 2.4: Hydrologic and Hydraulic Modeling Gap Analysis | 40
Table 41 presents gaps identified in the USACE River Basin Feasibility study modeling dataset.
Table 41: USACE River Basin Feasibility Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • Only two watersheds, Neuse (in Draft form) and Tar-Pamlico (in progress)
have been studied to date.
Level of Detail • None
Modeling Platform
Availability
• None
Flood Hazards Modeled • 1,000-yr (0.1% annual chance) not included as an extreme event
Future Conditions • Increases in future rainfall and/or development could be considered in
modeling.

The anticipated use and gaps for the USACE River Basin Feasibility modeling are similar to NCEM’s
basin mitigation modeling. The dataset provides valuable high-level hydrologic modeling that has
been calibrated to significant flooding events experienced within the watershed. These models were
used to analyze potential flood mitigation projects and could be used to analyze additional
alternatives as they are identified. The models are able to be manipulated to add more detail in areas
of interest or to model additional flooding scenarios including various future conditions. The largest
gap identified is scale/extent as not all basins in the state have been studied.
3.3 Other Potential Modeling Sources
As the Blueprint is implemented across each of the 17 basins, we will leverage the stakeholder
engagement process to identify additional sources of data within each basin that might add value to
the flood hazard identification and visualization as part of the flood resiliency process. Examples of
such datasets include:
• NC State University has completed flood mitigation studies in many watersheds including the
Cashie River basin.
• Duke Energy may have modeling for major hydroelectric dams.
• The Tennessee Valley Authority has H&H modeling for many streams and dams in the western
portion of the state .
• The Federal Energy Regulatory Commission may have available models for Dam Breach Analyses.
• USACE has Corps Water Management System models to support the regulation of flow through
reservoirs, locks, and other water control structures.
• USACE has performed H&H modeling for a portion of the Tar basin in support of a flood risk
management study for the Town of Princeville, NC. The study was conducted as a result of
Executive Order 13146 in February of 2000 which established the “President’s Council on the
Future of Princeville.” The study analyzed potential mitigation strategies such as raising roads,
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extending the existing levee, and installing culvert backflow devices to reduce flooding within the
Town.
• USGS has developed Soil and Water Assessment Tool (SWAT) water quantity models for the Yadkin-
Pee Dee and the Cape Fear watersheds.
• The Nature Conservancy is developing a SWAT model for the Cape Fear Basin.
• East Carolina University is developing a SWAT model of the Tar-Pamlico Basin .

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4 Nationwide/Regional Datasets
4.1 NOAA Office of Water Prediction National Water Model
The National Oceanic and Atmospheric Administration’s (NOAA’s) National Water Model (NWM)
simulates observed and forecast streamflow for over 3.4 million miles of streams and rivers across the
nation. The hydrologic model produces forecast streamflow for short (18 hours), medium (10 days),
and long (30 days) range. Output from the model is available in NetCDF format. Table 42 provides
summary information for the USACE river basin feasibility modeling. Figure 9 below provides a
representative view of the NWM at the North Carolina state scale.
Table 42: NOAA NWM Modeling Dataset Information
NOAA National Water Model
Source of Information NOAA
Link to Online Data https://water.noaa.gov/map
Data Owner NOAA
Date Created 2015
Date of Access February 2023
Frequency of Updates Uncertain. Data products are “live”
Update Needed No

Figure 9: The NWM provides statewide current and forecast streamflow estimates.
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Table 43 below summarizes the criteria used to perform the gap analysis.
Table 43: NOAA NWM Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age 2 years
Scale (Spatial Extent) Nationwide
Level of Detail Medium
Modeling Platform
Availability
Model not available, only model output/results . WRF-Hydro is the core model
used and is open source.
Flood Hazards Modeled Current observed and forecast stream flows provided are not tied to
probabilistic events.
Future Conditions Provides short, medium, and long-term forecasts out to 30 days. No “true”
future conditions that consider climate change are provided.

Table 44 presents gaps identified in the NOAA NWM modeling dataset.
Table 44: NOAA NWM Modeling Data Gaps
Identified Gaps
Age None
Scale (Spatial Extent) None
Level of Detail Streamflow estimates from NWM can vary from actual gauge readings at the
same location.
Modeling Platform
Availability
WRF-Hydro is open source, however, the NWM Model itself is not available,
only model products.
Flood Hazards Modeled Annual exceedance chance flows based on regression/gauge data for each
modeled reach added for reference could be particularly useful.
Future Conditions None

NOAA’s National Water Model provides estimates of real-time streamflow across the nation. As the
underlying model is not available for use/modification and the dataset does not include defined
annual exceedance flood events its usefulness in the Blueprint is anticipated to be minimal. However,
awareness of this tool, especially during flood events may be helpful and factor into decision-making
during emergency planning and response for flooding.
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4.2 National Weather Service River Forecast Centers
The NWS maintains 13 river forecast centers across the United States. North Carolina is primarily
covered by the Southeast River Forecast Center with the exception of the most western watersheds
that are within the Lower Mississippi River Forecast Center region. These centers provide river
forecasts that vary in time scale from hours to days to months. The most common product of
traditional flood forecasts is provided 5 days out to the general public, while as much as a yearly
outlook is provided for water management agencies. These centers are responsible for issuing flood
warnings for the protection of lives and property. Table 45 provides summary information for the NWS
river forecast centers modeling. Figure 10 below provides an overview of the river forecast centers
across the nation.
Table 45: NWS River Forecast Centers Modeling Dataset Information
National Weather Service River Forecast Centers
Source of Information National Weather Service
Link to Online Data https://water.weather.gov/ahps/rfc/rfc.php
Data Owner National Weather Service
Date Created 1971
Date of Access February 2023
Frequency of Updates Constant, in continuous operation.
Update Needed No

Figure 10: NWS River Forecast Regions across the Nation
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Table 46 below summarizes the criteria used to perform the gap analysis.
Table 46: NWS River Forecast Centers Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age NA – Forecast centers are in constant operation.
Scale (Spatial Extent) Statewide coverage, however actual forecast locations are fairly sparse and
limited to primarily large rivers. River Forecast Center site claims 217 sites
across the state (many not currently active).
Level of Detail High
Modeling Platform
Availability
Model not available, only model output/results.
Flood Hazards Modeled Current observed and forecast stream flows are not tied to probabilistic
(annual chance of exceedance) events.
Future Conditions Provides short, medium, and long-term forecasts but no “true” future
conditions that consider climate change are provided.

Table 47 presents gaps identified in the NWS River Forecast Centers modeling dataset.
Table 47: NWS River Forecast Centers Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • More forecast locations could be considered. The National Water Model
development may ultimately limit need for additional forecast points from
the River Forecast Centers.
Level of Detail • None
Modeling Platform
Availability
• Model not available, only model products.
Flood Hazards
Modeled
• None
Future Conditions • None

The NWS River Forecast Centers provide extremely valuable information for potential flood conditions
along major rivers across the country (including North Carolina). As the underlying models are not
available for use or modification outside of the NWS it is anticipated that their usefulness for the
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Blueprint will be minimal. Awareness of the forecast information provided by the river forecast
centers may however prove to be a valuable dataset to be considered in portions of the Blueprint.
4.3 Pacific Northwest National Laboratory Rapid Infrastructure
Flood Tool
Pacific Northwest National Laboratory (PNNL) developed the Rapid Infrastructure Flood Tool (RIFT) to
better prepare authorities, emergency responders, and communities prior to, during, and following
large-scale food events. The RIFT tool is a two-dimensional hydrodynamic model that estimates areas
that will be most impacted and aims to provide awareness to authorities to more effectively organize
and strategically place resources needed during flood response. Table 48 provides summary
information for the PNNL RIFT modeling. Figure 11 below provides a sample dataset from the RIFT
model output at the North Carolina state scale.
Table 48: PNNL RIFT Modeling Dataset Information
PNNL Rapid Infrastructure Flood Tool
Source of Information PNNL
Link to Online Data https://open-rift-pnnl.hub.arcgis.com/
Data Owner PNNL – United States Department of Energy
Date Created Varies – Event Specific
Date of Access February 2023
Frequency of Updates Uncertain. Data products are near “real-time.”
Update Needed No

Table 49 below summarizes the criteria used to perform the gap analysis.
Table 49: PNNL RIFT Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age Uncertain. Model runs are event specific.
Scale (Spatial Extent) Nationwide
Level of Detail Low. Approximately 300-ft model cell resolution stated in metadata, however,
smallest scale product cache appears to be ~2,500-ft cells.
Modeling Platform
Availability
Uncertain. Model not available, only model products.
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Gap Analysis Criteria
Flood Hazards Modeled Event-specific. Current and near-term forecast products are not tied to
probabilistic events.
Future Conditions None

Figure 11: PNNL RIFT Modeling Output for Hurricane Florence
Table 50 presents gaps identified in the PNNL RIFT modeling dataset.
Table 50: PNNL RIFT Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • None
Level of Detail • Model products are very coarse and largely unusable beyond identifying
areas to focus more refined modeling on. Products consistent with stated
model resolution (90-m) or refined post-processing of results could result
in data more actionable data for North Carolina.
Modeling Platform
Availability
• Model not available, only model products.
Flood Hazards Modeled • Model runs for annual exceedance chance events based on NOAA Atlas 14
rainfall intensity, duration, and frequency curves added for reference
could be particularly useful.
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Identified Gaps
Future Conditions • Model runs accounting for climate change for annual exceedance chance
events and/or past events could be performed.

The PNNL RIFT modeling is able to quickly provide a high-level understanding of where flooding is
anticipated to occur during major events. As the underlying model is not available for
use/modification and the dataset does not include defined annual exceedance flood events its
usefulness in the Blueprint is anticipated to be minimal. However, awareness of this tool, especially
during flood events may be helpful and factor into decision-making during emergency planning and
response for flooding. Although the model products are coarse, they can guide where to focus more
detailed modeling efforts using other datasets.
4.4 United States Geological Survey National Hydrologic Model
The USGS developed the National Hydrologic Model (NHM) to support efficient development of local-,
regional-, and national-scale hydrologic models across the nation. The NHM consists of three primary
parts: a geospatial fabric of modeling units (NHDPlus version 1 data), a model input data archive
(gridded climate datasets including Daymet and gridMET), and a repository of the physical model
code bases (Monthly Water Balance Model [MWBM] and Precipitation-Runoff Modeling System
[PRMS]) . Additional information regarding the use of the NHM can be found at the following links:
• http://pubs.er.usgs.gov/publication/tm6B9
• https://doi.org/10.1016/j.envsoft.2018.09.023
Table 51 provides summary information for the USGS NHM modeling.
Table 51: USGS NHM Modeling Dataset Information
USGS National Hydrologic Model
Source of Information USGS
Link to Online Data https://www.usgs.gov/mission-areas/water-resources/science/national-
hydrologic-model-infrastructure
Data Owner USGS
Date Created 2018
Date of Access February 2023
Frequency of Updates Daymet version is updated through 2019, GridMET version is updated annually
Update Needed Uncertain

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Table 52 below summarizes the criteria used to perform the gap analysis.
Table 52: USGS NHM Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age Supporting model last release date 2 years or less
Scale (Spatial Extent) Nationwide availability, but scalable with ability to extract subsets of the
national application to run locally for NC watersheds.
Level of Detail Flexible – Current NHM applications are to roughly a HUC 12 scale.
Modeling Platform
Availability
Open – MWBM: Monthly time step water balance model. McCabe and
Markstrom (2007)
PRMS: Daily time step process-based hydrologic model. Markstrom and others
(2015); Leavesley and others (1983).
Flood Hazards Modeled Flexible. No established model results available. NHM-PRMS temporal
resolution is daily timestep.
Future Conditions Yes. Ongoing work through USGS Southeast Climate Adaptation Science
Center is producing future simulations through the year 2100. NHM-PRMS and
MWBM are compatible with various downscaled General Circulation Model
outputs.

Table 53 presents gaps identified in the USGS NHM modeling dataset.
Table 53: USGS NHM Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • None
Level of Detail • Current applications to roughly a HUC 12 scale. Newer versions will
provide more detail and new tools will allow for different spatial unit
resolutions.
Modeling Platform
Availability
• None
Flood Hazards Modeled • Pre-determined model results for annual exceedance chance events of
interest not available but would be useful.
Future Conditions • Pre-determined model results for future conditions of interest not
available but would be useful.

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The USGS National Hydrologic Model is a support tool to help develop hydrologic models. This toolset
may be helpful for the development of new hydrologic models if needed as part of Blueprint.
4.5 United States Army Corps of Engineers South Atlantic
Coastal Study
Following the 2017 hurricane season, congress passed the Bipartisan Budget Act of 2018 which
provided funds for the South Atlantic Coastal Study (SACS). Based on the USACE report, the SACS is a
comprehensive study that applies watershed planning concepts to identify actions for advancing
coastal resilience. The SACS included a Tier 1 Risk Assessment for the coast of North Carolina that
included water levels for the 10% annual exceedance probability (AEP) from the USACE Engineering
Research and Development Center (ERDC), 1 percent AEP from FEMA’s National Flood Hazard Layer as
well as a Category 5 hurricane Maximum of Maximum from NOAA’s Sea, Land, and Overland Surges
from Hurricanes (SLOSH) model. In addition, the Coastal Hazards System provided refinements to the
Tier 1 hazard data with coupled hydrodynamic (ADCIRC) and wave (Steady-state spectral WAVE
[STWAVE]) models populated with the most up-to-date elevation data and calibrated based on
observed events. This modeling provided simulations for present-day mean sea level and two sea
level rise (SLR) scenarios based on USACE estimates for intermediate and high SLR.
Table 54 provides summary information for the USACE SACS modeling.
Table 54: USACE SACS Coastal Modeling Dataset Information
USACE SACS Coastal Modeling
Source of Information United States Army Corps of Engineers
Link to Online Data https://www.sad.usace.army.mil/SACS/
https://chs.erdc.dren.mil
Data Owner United States Army Corps of Engineers
Date Created October 2021
Date of Access August 2023
Frequency of Updates Unknown
Update Needed No

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Table 55 below summarizes the criteria used to perform the gap analysis.
Table 55: USACE SACS Coastal Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age 2 years
Scale (Spatial Extent) Southeast US Coast (including entire NC coast)
Level of Detail High
Modeling Platform
Availability
ADCIRC and STWAVE are both open source; however, SMS (which is
proprietary) is widely considered necessary for model use.
Flood Hazards Modeled 1% annual chance
Future Conditions Yes – 2 sea level rise scenarios

Table 56 presents gaps identified in the USACE SACS Coastal modeling dataset.
Table 56: USACE SACS Coastal Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • None
Level of Detail • None
Modeling Platform
Availability
• The coastal models require supercomputers for computations.
Flood Hazards Modeled • Uncertain but documentation indicates AEP data is available. Need to
confirm with additional research/coordination.
Future Conditions • None

The USACE SACS coastal modeling and associated study is a fairly recent, highly detailed resource
focused on increasing coastal resilience. This resource/dataset has the potential to provide valuable
input to Blueprint efforts within the coastal region.
4.6 National Oceanic and Atmospheric Administration Sea, Lake,
and Overland Surges from Hurricanes Modeling
The NWS developed the SLOSH model to estimate storm surge heights resulting from historical,
hypothetical, or predicted hurricanes. The model is used to perform simulation studies for hurricane
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evacuation planning by FEMA, USACE, and emergency managers. In addition, the model is run by the
National Hurricane Center (NHC) for real-time awareness when storms are threatening. To help
reduce potential error that may occur with a single deterministic model run, the Probabilistic Storm
Surge Model (P-Surge) relies on an ensemble of SLOSH runs based on past forecast performance.
NOAA displays SLOSH model results on an experimental interactive website for P-Surge which
includes past historic events. A SLOSH Display Program (SDP) is also available to display results of the
SLOSH model.
Table 57 provides summary information for the NOAA SLOSH modeling.
Table 57: NOAA SLOSH Modeling Dataset Information
NOAA SLOSH Coastal Modeling
Source of Information NOAA/NWS
Link to Online Data https://www.nhc.noaa.gov/surge/slosh.php
https://slosh.nws.noaa.gov/sdp/index.php
https://slosh.nws.noaa.gov/psurge/index.php
Data Owner NOAA
Date Created Model was developed in 1990s, but model runs are performed as needed and
real-time during NHC advisories.
Date of Access August 2023
Frequency of Updates SLOSH model coverage is divided into 32 regions/basins. Typically, 3-6 basins
are updated per year based on changes in topography/bathymetry from
storms, vulnerability to storm surge, new data availability, and changes to the
coast including the addition of engineered flood protection devices. Model
results are available real-time during coastal storm events.
Update Needed No

Table 58 below summarizes the criteria used to perform the gap analysis.
Table 58: NOAA SLOSH Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age Although the actual model is dated, model input for the 32 basins is updated
cyclically each year based on factors outlined above. Model runs are
performed as needed and real-time during NHC advisories.
Scale (Spatial Extent) Nationwide (including entire NC coast)
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Gap Analysis Criteria
Level of Detail High, but dependent upon base data (topography/bathymetry), used grid cell
size (which are smaller closer to shore), and inclusion of major barriers and
narrow canals/rivers. Accuracy of model results is estimated to be within
about 20% of actual conditions. Inundation mapping results available on P-
Surge website are coarse, however, experimental inundation mapping with
higher precision is made available during NHC advisory model runs.
Modeling Platform
Availability
SLOSH model results are publicly available through the P-Surge website and
by using the SDP.
Flood Hazards Modeled Coastal storm surge with probabilities of exceedance for various surge levels
(5 feet operationally and 2 through 10 feet experimentally)
Future Conditions None readily available, however, the SLOSH model can be used to model
storm surge for hypothetical events.

Table 59 presents gaps identified in the NOAA SLOSH Coastal modeling dataset.
Table 59: NOAA SLOSH Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • None
Level of Detail • None
Modeling Platform
Availability
• The coastal models require supercomputers for efficient computations.
Flood Hazards Modeled • Various probabilities of exceedance for storm surge associated with an
ongoing event are provided, however, AEP events do not appear to be
available.
• Model does not include wave action or interaction/influence of fluvial or
pluvial flooding from rivers and rainfall.
Future Conditions • No defined future conditions model runs are identified; however, the
model could be used to compute hypothetical future events if provided
with necessary input data from other sources that estimate future
atmospheric conditions.

The NOAA SLOSH coastal modeling provides an extremely valuable tool for hurricane evacuation
planning and real-time awareness of potential storm surge impacts from hurricanes and other
significant coastal storms. The probabilistic modeling approach is less vulnerable to prediction error
than a single deterministic model but can be more difficult to interpret. Model runs for typical AEP
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events based on previously completed computations for past storms and hypothetical future events
could provide valuable information for the Blueprint within the coastal region.
4.7 University of North Carolina Renaissance Computing Institute
ADCIRC Prediction System Modeling
ADCIRC was developed in the 1990s by Dr. Rich Luettich to model coastal circulation and storm surge
water levels and currents. The model is used today by the USACE ERDC (see SACS section above),
FEMA, and various universities including the University of North Carolina (UNC). UNC’s Renaissance
Computing Institute (RENCI) specifically uses the ADCIRC Prediction System (APS) to manage ADCIRC
model runs on High Performance Computing systems. Model runs are generated daily based on North
American Mesoscale Forecast System forecasts and when the NHC issues storm advisories. Although
ADCIRC models are also run by other entities including Louisiana State University for publication to
the Coastal Emergency Risk Assessment (CERA) web application, the model computed by RENCI uses
a more refined/detailed mesh for North and South Carolina. The ADCIRC model is certified by FEMA for
coastal surge analyses and has been used in many flood studies across the country, including North
Carolina. The model is typically regarded as more complex and capable, although more time
consuming and computational demanding than the SLOSH model.
Table 60 provides summary information for the RENCI ADCIRC modeling.
Table 60: RENCI ADCIRC Modeling Dataset Information
RENCI ADCIRC Coastal Modeling
Source of Information UNC RENCI/USACE
Link to Online Data https://apsviz-terria-map-dev.apps.renci.org
Data Owner UNC RENCI
Date Created The original model was developed in the 1990s but has had many updates
with the latest version (53) released in 2018. Model runs are performed as
needed with best available data and real-time during NHC advisories.
Date of Access August 2023
Frequency of Updates Recent model versions have been released roughly every two to five years.
Model results are available real-time during coastal storm events.
Update Needed No

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Table 61 below summarizes the criteria used to perform the gap analysis.
Table 61: RENCI ADCIRC Modeling Gap Analysis Criteria Summary
Gap Analysis Criteria
Age Most recent version (53) is 5 years old. Age of model runs/results are user
dependent, and some are available daily.
Scale (Spatial Extent) Nationwide (including entire NC coast)
Level of Detail High, but dependent upon accuracy of base data (topography/bathymetry)
and forcing factors such as storm track and wind intensity as well as used
mesh cell size (which are smaller closer to shore. Inundation mapping results
available on CERA and APS visualization system (APSViz) websites are coarse,
however, improved mapping is possible using the model results and high-
resolution topography.
Modeling Platform
Availability
ADCIRC is free; however, SMS (which is proprietary) is considered necessary
for computations. ADCIRC model results are publicly available through the
APSViz and CERA websites.
Flood Hazards Modeled Coastal storm surge. Also, can be paired with wave models such as SWAN or
STWAVE for wave simulations. Multiple AEP scenarios such as those used in
FEMA studies can be developed.
Future Conditions None readily available, however, the ADCRIC model can be used to model
storm surge for hypothetical events.

Table 62 presents gaps identified in the RENCI ADCIRC Coastal modeling dataset.
Table 62: RENCI ADCIRC Modeling Data Gaps
Identified Gaps
Age • None
Scale (Spatial Extent) • None
Level of Detail • None
Modeling Platform
Availability
• The coastal models require supercomputers for efficient computations.
• Proprietary software (SMS) is considered necessary for model use.
Flood Hazards Modeled • Model does not include interaction/influence of fluvial or pluvial flooding
from rivers and rainfall.
Future Conditions • No defined future conditions model runs identified; however, the model
could be used to compute hypothetical future events if provided with
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Identified Gaps
necessary input data from other sources that estimate future atmospheric
conditions.

The RENCI ADCIRC coastal modeling provides an extremely valuable tool for real-time awareness of
potential storm surge impacts from hurricanes and other significant coastal storms. Many coastal
studies performed by USACE and FEMA have used the ADCIRC model to develop coastal storm surge
hazard information at various AEPs for risk assessments and design considerations. Although
considered more complex and capable than the SLOSH model, it typically takes longer to run which is
a disadvantage during storm preparations/planning. In addition, as a deterministic model, it is more
susceptible to error with input data. Model runs for typical AEP events based on previously completed
computations for past storms (hindcasts) and hypothetical future events could provide valuable
information for the Blueprint within the coastal region.