ROWAN-007 Final Report

DAM HYDRAULIC CAPACITY
ASSESSMENT REPORT
(DRAFT)

LAKE KANNAPOLIS DAM

ROWAN-007

ROWAN COUNTY, NC

PREPARED BY:
HDR Engineering Inc. of the Carolinas
under contract with
WOOD E&I Solutions

2020

EXECUTIVE SUMMARY
A hydraulic capacity analysis was completed for the Lake Kannapolis Dam in Rowan County, North
Carolina. The purpose of the study was to analyze the existing potential of the dam for
overtopping during predetermined specified rainfall events using the North Carolina Dam Safety
defined process and templates. The analyses were completed using the United States Army Corps
of Engineers developed software Hydrologic Engineering Center – Hydrologic Modeling System
(HEC-HMS) in combination with Arc-GIS to develop required input parameters. The rainfall
events included in the analyses consist of 24-hour durations with return periods of 25 years, 50
years, 100 years, 200 years, 500 years and 1000 years. Results of the analyses indicate that this
structure is hydraulically adequate for 25 years, 50 years, 100 years, 200 years, 500 years, and
1000 years rainfall events. Data, input parameters, and final results can be found on the attached
summary sheets and in the appendices of this report as well as in the associated electronic file in
which all program files are stored.
Drainage Area (Sq. Mi.)=
Curve Number =
Lag Time (min.)=
Rainfall Distribution Methods =
12611.9
10421.6
10772.1
11128.6
11490.8
11858.8
12232.4
748.3
748.8
749.3
749.8
750.3
1076.8
1244.4
1415.7
ELEVATION
745.8
746.3
746.8
747.3
747.8
729.8
726.8
727.3
727.8
728.3
728.8
729.3
725.3
NA
ELEVATION
725.3
725.8
726.3
STORAGE (ACRE-FT)
9403.8
9737.5
10076.7
STORAGE (ACRE-FT)
0.0
144.9
291.9
441.4
594.7
751.9
912.6
69.26
149
SCS Type 2
SPILLWAY
Primary
Auxiliary
TYPE
Concrete Chute
NA
ELEVATION
SUMMARY OF INPUT PARAMETERS
10.51
SUMMARY SHEET OF HYDRAULIC CAPACITY RESULTS
LAKE KANNAPOLIS DAM, ROWAN-007
ANALYSIS PERFORMED BY: S. MURPHY, HDR
24 HOUR - 200 YEAR EVENT, 8.13 INCHES, ELEVATION 729.4 (3.6 FT FREE-BOARD)
24 HOUR - 100 YEAR EVENT, 7.35 INCHES, ELEVATION 728.9 (4.1 FT FREE-BOARD)
24 HOUR - 50 YEAR EVENT, 6.59 INCHES, ELEVATION 728.4 (4.6 FT FREE-BOARD)
24 HOUR - 25 YEAR EVENT, 5.85 INCHES, ELEVATION 727.9 (5.1 FT FREE-BOARD)
TOP OF DAM ELEVATION = 733
24 HOUR - 1000 YEAR EVENT, 10 INCHES, ELEVATION 730.6 (2.4 FT FREE-BOARD)
24 HOUR - 500 YEAR EVENT, 9.19 INCHES, ELEVATION 730.1 (2.9 FT FREE-BOARD)
ROWAN-007LAKE KANNAPOLIS DAM SEPTEMBER 10, 2020
26863.1
NOT TO SCALE
23530.8
24067.9
24612.9
25165.1
25724.2
26290.2764.8
765.3
9075.8
744.8
745.3
742.3
742.8
743.3
743.8
744.3
763.3
763.8
764.38124.1
20454.5
20949.7
21451.9
21961.0
22477.2
23000.5
17622.6
18078.8
18541.0
19009.5
19484.6
19966.2
15857.7
16289.9
16728.1
17172.4
12997.0
13388.1
13785.0
14187.7
14596.3
760.3
760.8
761.3
761.8
762.3
762.8
751.3
751.8
752.3
752.8
753.3
753.8
755.8
756.3
756.8
757.3
757.8
758.3
758.8
759.3
759.8
754.3
754.8
755.3
15010.9
15431.4
750.8
8436.2
8753.4
7220.8
7516.3
7817.4
2737.5
2947.0
3161.0
1590.8
1769.8
1953.1
6366.1
6645.9
6930.8
4790.6
5041.0
5296.1
5556.1
5821.1
6091.1
3380.4
3604.7
3833.2
4066.0
4303.1
4544.6
2140.6
2332.5
2532.3
741.8
738.8
739.3
739.8
740.3
740.8
741.3
735.8
736.3
736.8
737.3
737.8
738.3
734.3
734.8
735.3
730.3
730.8
731.3
731.8
732.3
732.8
733.3
733.8
ROWAN-007LAKE KANNAPOLIS DAM SEPTEMBER 10, 2020

APPENDIX A
Watershed Boundary

Sources: Esri, HERE, Garmin, USGS, Intermap, INCREMENT P,NRCan, Esri Japan, METI, Esri China (Hong Kong), Esri Korea,Esri (Thailand), NGCC, (c) OpenStreetMap contributors, and theGIS User Community
Lake Kannapolis Dam - ROWAN-007 - Watershed Boundary
Legend
LongestFlowPath
WatershedBoundary
0 1 20.5 Miles
Date: 8/30/2020
/Drainage Ar ea: 10.51 Square MilesFlowpath Length: 32500.9 feet

APPENDIX B

Lag Time Calculation
Dam No:ROWAN-007 Date:9/4/2020
Dam Name:Lake Kannapolis Dam Engineer:K. Trefzger
Maximum Potential Retention (inches):S =(1000/cn')-10
Time of Concentration (hours):Tc =l0.8*(S+1)0.7
1140*Y0.5
Basin Data:Input Values in yellow
Curve Number CN =69.2626 from NRCS CN Calculation
S =4.4378 in.
Mean Basin Slope Y =7.96714 %from Watershed Mean slope
Longest Flowpath:6.15547 mi.from Watershed Longest flowpath
Flow Length l =32500.9 ft.
Time of Concentration Tc =4.14 Hours Tc =248 mins
Lag Time TL =2.48 Hours TL =149 mins

APPENDIX C
NRCS Curve Number Summary Sheet

Change CN according to TR-55 (see tables below)
NLCD (2016) Landuse TR-55 Landuse HSG A (sq. ft.)CN HSG B (sq. ft.)CN HSG C (sq. ft.)CN HSG D (sq. ft.)CN
Open Water Not Available 0 100 0 636811 100 63681148 4199 100 419919 11053033 100 #########
Developed, Open Space Open space - Fair condition (grass cover 50% to 75%)0 49 0 53478513 69 3690017431 8194217 79 647343158 1498376 84 125863620
Developed, Low Intensity Residential districts by average lot size: 1/3 acre 0 57 0 12489033 72 899210368 2326085 81 188412917 348932 86 30008169
Developed, Medium Intensity Residential districts by average lot size: 1/8 acre 0 77 0 1127730 85 95857081 268120 90 24130771 126359 92 11625041
Developed, High Intensity Urban districts - Commercial and business 0 89 0 77765 92 7154402 19370 94 1820822 18999 95 1804927
Barren Land Newly graded areas 0 77 0 19371 86 1665869 0 91 0 0 94 0
Deciduous Forest Woods - Fair 0 36 0 68566419 60 4113985124 4718746 73 344468451 4761555 79 376162879
Evergreen Forest Woods - Fair 0 36 0 16042795 60 962567706 1523683 73 111228833 445502 79 35194650
Mixed Forest Woods - Fair 0 36 0 15061199 60 903671933 1187713 73 86703048 1091137 79 86199843
Shrub/Scrub Brush - Fair 0 35 0 4333498 56 242675863 13169 70 921815 31072 77 2392572
Herbaceuous Herbaceuous - Fair 0 60 0 3246774 71 230520984 67608 81 5476252 491926 89 43781432
Hay/Pasture Pasture - Fair 0 49 0 51707010 69 3567783679 4625865 79 365443299 2928420 84 245987301
Cultivated Crops Row crops (SR + CR) - Poor 0 71 0 15459400 80 1236752035 4621838 87 402099886 334079 90 30067112
Woody Wetlands Not Available 0 80 0 17108 85 1454163 0 90 0 60374 95 5735542
Emergent Herbaceuous Wetlands Not Available 0 80 0 0 85 0 0 90 0 0 95 0 Weighted CN=69.26
NOTE: Curve Numbers are from SCS TR-55 with the exception of assumed HSG A (CN=60) for Herbaceous,Open Water, Woody Wetlands, and Emergent Herbaceous
Wetlands.
NOTE: double-check all the land types are being calculated and texts are accurate
NOTE: double-check the exported attribute table has the same table format as the "Export_Output" table

APPENDIX D
Hyetograph Results Used for Analysis

0.0
2.0
4.0
6.0
8.0
10.0
12.0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Cumulative Depth (in)Time (hrs)
Hyetographs for 24-Hour SCS Type II Rainfall Distributions
25YR
50YR
100YR
200YR
500YR
1000YR

APPENDIX E
NOAA Atlas 14 Rainfall Table

Point precipitation frequency estimates (inches)
NOAA Atlas 14 Volume 2 Version 3
Data type: Precipitation depth
Time series type: Partial duration
Project area: Ohio River Basin
Location name (ESRI Maps): China Grove, North Carolina USA
Station Name: -
Latitude: 35.544999°
Longitude: -80.651957°
Elevation (USGS): 797.63 ft
PRECIPITATION FREQUENCY ESTIMATES
by
duration
for ARI
(years):1 2 5 10 25 50 100 200 500 1000
5-min:0.39 0.461 0.537 0.592 0.654 0.696 0.734 0.768 0.805 0.83
10-min:0.622 0.737 0.861 0.947 1.04 1.11 1.17 1.22 1.27 1.31
15-min:0.778 0.926 1.09 1.2 1.32 1.4 1.47 1.54 1.6 1.64
30-min:1.07 1.28 1.55 1.74 1.96 2.11 2.26 2.39 2.55 2.66
60-min:1.33 1.61 1.98 2.26 2.6 2.86 3.11 3.35 3.66 3.88
2-hr:1.54 1.86 2.31 2.66 3.1 3.43 3.76 4.09 4.52 4.84
3-hr:1.64 1.98 2.48 2.86 3.36 3.76 4.16 4.56 5.11 5.53
6-hr:2 2.41 3.01 3.48 4.11 4.61 5.11 5.63 6.34 6.89
12-hr:2.37 2.86 3.58 4.16 4.95 5.58 6.23 6.91 7.85 8.59
24-hr:2.8 3.38 4.25 4.93 5.85 6.59 7.35 8.13 9.19 10
2-day:3.27 3.94 4.91 5.67 6.7 7.52 8.35 9.21 10.4 11.3
3-day:3.47 4.18 5.18 5.97 7.04 7.89 8.76 9.65 10.9 11.8
4-day:3.68 4.41 5.45 6.26 7.37 8.26 9.16 10.1 11.4 12.3
7-day:4.24 5.06 6.16 7.03 8.23 9.18 10.1 11.1 12.5 13.6
10-day:4.85 5.77 6.94 7.85 9.07 10 11 12 13.3 14.3
20-day:6.52 7.7 9.08 10.2 11.6 12.8 13.9 15.1 16.7 17.9
30-day:8.04 9.46 11 12.2 13.7 14.9 16.1 17.2 18.8 19.9
45-day:10.1 11.8 13.5 14.8 16.4 17.7 18.9 20.1 21.7 22.8
60-day:12.1 14.1 15.9 17.3 19.1 20.4 21.7 23 24.6 25.8
Date/time (GMT): Tue Oct 13 19:27:11 2020
pyRunTime: 0.017315864563

APPENDIX F
Outlet Works Rating Curves

Total outlet discharge from the spillway system
Client:NCEM Date:9/4/2020
Project:Overtopping Study Engineer:E.Torrey
Dam:Lake Kannapolis Dam Dam No.ROWAN-007
Reservior Water
Level (RWS)
Elevation (ft)
Primary spillway
discharge (cfs)
Emergency spillway
discharge (cfs)
Total discharge from the
spillway system (cfs)
725.3 0.0 0.0 0.0
725.8 87.7 0.0 87.7
726.3 248.0 0.0 248.0
726.8 455.6 0.0 455.6
727.3 701.4 0.0 701.4
727.8 980.3 0.0 980.3
728.3 1288.6 0.0 1288.6
728.8 1623.9 0.0 1623.9
729.3 1984.0 0.0 1984.0
729.8 2367.4 0.0 2367.4
730.3 2772.7 0.0 2772.7
730.8 3198.9 0.0 3198.9
731.3 3644.8 0.0 3644.8
731.8 4109.8 0.0 4109.8
732.3 4593.0 0.0 4593.0
732.8 5093.8 0.0 5093.8
733.3 5611.6 0.0 5611.6
733.8 6145.8 0.0 6145.8
734.3 6696.0 0.0 6696.0
734.8 7261.7 0.0 7261.7
735.3 7842.4 0.0 7842.4
735.8 8437.9 0.0 8437.9
736.3 9047.8 0.0 9047.8
736.8 9671.6 0.0 9671.6
737.3 10309.2 0.0 10309.2
737.8 10960.2 0.0 10960.2
738.3 11624.3 0.0 11624.3
738.8 12301.3 0.0 12301.3
739.3 12991.0 0.0 12991.0
739.8 13693.2 0.0 13693.2
740.3 14407.5 0.0 14407.5
740.8 15133.8 0.0 15133.8
741.3 15872.0 0.0 15872.0
741.8 16621.8 0.0 16621.8
742.3 17383.0 0.0 17383.0
742.8 18155.5 0.0 18155.5
743.3 18939.1 0.0 18939.1
743.8 19733.7 0.0 19733.7
744.3 20539.1 0.0 20539.1
744.8 21355.2 0.0 21355.2
745.3 22181.8 0.0 22181.8
745.8 23018.8 0.0 23018.8
746.3 23866.1 0.0 23866.1
746.8 24723.5 0.0 24723.5
747.3 25590.9 0.0 25590.9
0.0
5000.0
10000.0
15000.0
20000.0
25000.0
30000.0
720.0 725.0 730.0 735.0 740.0 745.0 750.0Total discharge from the spillway system (cfs)Reservior Water Level (RWS) Elevation (ft)
The whole spillway system rating curve (cfs)