ROWAN-006 Final Report

DAM HYDRAULIC CAPACITY
ASSESSMENT REPORT
(DRAFT)

LANDIS WATER RESERVOIR DAM

ROWAN-006

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 Landis Water Reservoir 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 =
24 HOUR - 200 YEAR EVENT, 8.02 INCHES, ELEVATION 801.8 (5.2 FT FREE-BOARD)
24 HOUR - 100 YEAR EVENT, 7.26 INCHES, ELEVATION 801.4 (5.6 FT FREE-BOARD)
24 HOUR - 50 YEAR EVENT, 6.52 INCHES, ELEVATION 800.9 (6.1 FT FREE-BOARD)
24 HOUR - 25 YEAR EVENT, 5.79 INCHES, ELEVATION 800.5 (6.5 FT FREE-BOARD)
SUMMARY OF INPUT PARAMETERS
1.88
SUMMARY SHEET OF HYDRAULIC CAPACITY RESULTS
LANDIS WATER RESERVOIR DAM, ROWAN-006
ANALYSIS PERFORMED BY: S. MURPHY, HDR
TOP OF DAM ELEVATION = 807
24 HOUR - 1000 YEAR EVENT, 9.89 INCHES, ELEVATION 802.8 (4.2 FT FREE-BOARD)
24 HOUR - 500 YEAR EVENT, 9.07 INCHES, ELEVATION 802.3 (4.7 FT FREE-BOARD)
71.71
76
SCS Type 2
SPILLWAY
Primary
Auxiliary
TYPE
Concrete Chute
NA
ELEVATION
799.6
800.1
800.6
801.1
801.6
802.1
798.1
NA
ELEVATION
798.1
798.6
799.1
STORAGE (ACRE-FT)
1616.1
1687.0
1760.2
STORAGE (ACRE-FT)
0.0
17.2
35.7
54.8
74.6
95.1
116.2
802.6
ELEVATION
818.6
819.1
819.6
820.1
820.6
138.1
160.8
184.4
1835.6
1912.9
1992.0
2073.0
2155.9
2240.7
821.1
821.6
822.1
822.6
823.1 2327.3
ROWAN-006LANDIS WATER RESERVOIR DAM SEPTEMBER 10, 2020
807.1
807.6
808.1
803.1
803.6
804.1
804.6
805.1
805.6
806.1
806.6
814.6
811.6
812.1
812.6
813.1
813.6
814.1
808.6
809.1
809.6
810.1
810.6
811.1
1003.8
1057.0
1111.7
717.5
761.6
807.2
854.1
902.5
952.4
480.1
516.3
553.9
592.8
633.0
674.6
289.2
318.0
348.0
1414.0
1479.7
1168.2
1227.2
1287.7
379.1
411.5
445.1
209.0
234.7
261.4
2890.4
2993.0
823.6
833.1
833.6
834.1
834.6
835.1
835.6
824.1
824.6
825.1
825.6
826.1
826.6
828.6
829.1
829.6
830.1
830.6
831.1
831.6
832.1
832.6
827.1
827.6
828.1
3097.9
3205.1
3314.7
3426.9
2415.7
2506.1
2598.3
2692.6
2789.9
4278.7
4410.3
4544.3
4680.6
4819.8
4961.4
3541.6
3658.6
3777.9
3899.5
4023.5
4149.8
6027.6
NOT TO SCALE
5105.5
5251.9
5401.3
5553.7
5709.0
5866.9837.6
838.1
1547.0
817.6
818.1
815.1
815.6
816.1
816.6
817.1
836.1
836.6
837.11350.0
ROWAN-006LANDIS WATER RESERVOIR 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
Landis Water Reservior Dam - ROWAN-006 - Watershed Boundary
Legend
LongestFlowPath
WatershedBoundary
0 0.35 0.70.175 Miles
Date: 9/9/2020
/Drainage Area: 1.88 Square MilesFlowpath Length: 12038.2 feet

APPENDIX B
Lag Time Calculation

Dam No:ROWAN-006 Date:9/4/2020
Dam Name:Landis Water Reservoir 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 =71.7119 from NRCS CN Calculation
S =3.94469 in.
Mean Basin Slope Y =5.49974 %from Watershed Mean slope
Longest Flowpath:2.27997 mi.from Watershed Longest flowpath
Flow Length l =12038.2 ft.
Time of Concentration Tc =2.11 Hours Tc =126 mins
Lag Time TL =1.26 Hours TL =76 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 208669 100 20866917 5093 100 509319 1282931 100 128293069
Developed, Open Space Open space - Fair condition (grass cover 50% to 75%)0 49 0 6294522 69 434322024 230581 79 18215868 479601 84 40286488
Developed, Low Intensity Residential districts by average lot size: 1/3 acre 0 57 0 1316103 72 94759450 17586 81 1424505 187567 86 16130783
Developed, Medium Intensity Residential districts by average lot size: 1/8 acre 0 77 0 235885 85 20050247 0 90 0 19050 92 1752628
Developed, High Intensity Urban districts - Commercial and business 0 89 0 48427 92 4455240 0 94 0 0 95 0
Barren Land Newly graded areas 0 77 0 0 86 0 0 91 0 0 94 0
Deciduous Forest Woods - Fair 0 36 0 9618528 60 577111658 797806 73 58239821 804536 79 63558352
Evergreen Forest Woods - Fair 0 36 0 1877923 60 112675400 676203 73 49362790 78194 79 6177291
Mixed Forest Woods - Fair 0 36 0 1580534 60 94832020 292531 73 21354769 10571 79 835144
Shrub/Scrub Brush - Fair 0 35 0 145048 56 8122669 0 70 0 232 77 17879
Herbaceuous Herbaceuous - Fair 0 60 0 267502 71 18992660 166926 81 13520973 133901 89 11917212
Hay/Pasture Pasture - Fair 0 49 0 12490215 69 861824848 2164155 79 170968240 1257382 84 105620076
Cultivated Crops Row crops (SR + CR) - Poor 0 71 0 7008738 80 560699073 1550735 87 134913908 1212224 90 109100196
Woody Wetlands Not Available 0 80 0 3498 85 297362 0 90 0 35243 95 3348080
Emergent Herbaceuous Wetlands Not Available 0 80 0 566 85 48082 0 90 0 9120 95 866368 Weighted CN=71.71
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: 35.585°
Longitude: -80.634°
Elevation (USGS): 773.32 ft
PRECIPITATION FREQUENCY ESTIMATES
by
duration
for ARI
(years):1 2 5 10 25 50 100 200 500 1000
5-min:0.387 0.457 0.534 0.588 0.649 0.691 0.729 0.762 0.798 0.823
10-min:0.618 0.732 0.855 0.941 1.04 1.1 1.16 1.21 1.26 1.3
15-min:0.773 0.92 1.08 1.19 1.31 1.39 1.46 1.52 1.59 1.63
30-min:1.06 1.27 1.54 1.72 1.94 2.1 2.24 2.37 2.53 2.63
60-min:1.32 1.59 1.97 2.25 2.59 2.84 3.09 3.33 3.63 3.84
2-hr:1.53 1.85 2.3 2.64 3.08 3.41 3.74 4.06 4.48 4.79
3-hr:1.63 1.97 2.46 2.83 3.33 3.73 4.12 4.51 5.04 5.45
6-hr:1.98 2.39 2.98 3.45 4.07 4.56 5.06 5.57 6.27 6.8
12-hr:2.34 2.83 3.54 4.11 4.89 5.51 6.16 6.82 7.73 8.45
24-hr:2.77 3.34 4.2 4.87 5.79 6.52 7.26 8.02 9.07 9.89
2-day:3.23 3.89 4.84 5.59 6.61 7.41 8.22 9.06 10.2 11.1
3-day:3.43 4.12 5.11 5.89 6.94 7.78 8.63 9.5 10.7 11.6
4-day:3.63 4.36 5.38 6.18 7.27 8.14 9.03 9.93 11.2 12.1
7-day:4.19 5 6.09 6.95 8.12 9.05 10 11 12.3 13.3
10-day:4.79 5.7 6.85 7.75 8.95 9.89 10.8 11.8 13.1 14.1
20-day:6.44 7.61 8.97 10.1 11.5 12.6 13.8 14.9 16.5 17.7
30-day:7.96 9.37 10.9 12 13.6 14.7 15.9 17 18.5 19.7
45-day:10 11.7 13.4 14.6 16.3 17.5 18.7 19.9 21.4 22.5
60-day:11.9 13.9 15.7 17.1 18.8 20.2 21.4 22.7 24.3 25.5
Date/time (GMT): Fri Aug 28 16:03:56 2020
pyRunTime: 0.0444021224976

APPENDIX F
Outlet Works Rating Curves

Total outlet discharge from the spillway system
Client:NCEM Date:9/8/2020
Project:Overtopping Study Engineer:E.Torrey
Dam:Landis Water Reservoir Dam Dam No.ROWAN-006
Reservior Water
Level (RWS)
Elevation (ft)
Primary spillway
discharge (cfs)
Emergency spillway
discharge (cfs)
Total discharge from the
spillway system (cfs)
798.1 0.0 0.0 0.0
798.6 54.8 0.0 54.8
799.1 155.0 0.0 155.0
799.6 284.8 0.0 284.8
800.1 438.4 0.0 438.4
800.6 612.7 0.0 612.7
801.1 805.4 0.0 805.4
801.6 1014.9 0.0 1014.9
802.1 1240.0 0.0 1240.0
802.6 1479.6 0.0 1479.6
803.1 1733.0 0.0 1733.0
803.6 1999.3 0.0 1999.3
804.1 2278.0 0.0 2278.0
804.6 2568.6 0.0 2568.6
805.1 2870.6 0.0 2870.6
805.6 3183.6 0.0 3183.6
806.1 3507.2 0.0 3507.2
806.6 3841.1 0.0 3841.1
807.1 4185.0 0.0 4185.0
807.6 4538.5 0.0 4538.5
808.1 4901.5 0.0 4901.5
808.6 5273.7 0.0 5273.7
809.1 5654.8 0.0 5654.8
809.6 6044.8 0.0 6044.8
810.1 6443.2 0.0 6443.2
810.6 6850.1 0.0 6850.1
811.1 7265.2 0.0 7265.2
811.6 7688.3 0.0 7688.3
812.1 8119.4 0.0 8119.4
812.6 8558.2 0.0 8558.2
813.1 9004.7 0.0 9004.7
813.6 9458.7 0.0 9458.7
814.1 9920.0 0.0 9920.0
814.6 10388.6 0.0 10388.6
815.1 10864.4 0.0 10864.4
815.6 11347.2 0.0 11347.2
816.1 11837.0 0.0 11837.0
816.6 12333.6 0.0 12333.6
817.1 12837.0 0.0 12837.0
817.6 13347.0 0.0 13347.0
818.1 13863.6 0.0 13863.6
818.6 14386.7 0.0 14386.7
819.1 14916.3 0.0 14916.3
819.6 15452.2 0.0 15452.2
820.1 15994.3 0.0 15994.3
0.0
2000.0
4000.0
6000.0
8000.0
10000.0
12000.0
14000.0
16000.0
18000.0
795.0 800.0 805.0 810.0 815.0 820.0 825.0Total discharge from the spillway system (cfs)Reservior Water Level (RWS) Elevation (ft)
The whole spillway system rating curve (cfs)