ROWAN-005 Final Report

DAM HYDRAULIC CAPACITY
ASSESSMENT REPORT
(DRAFT)
ROWAN COUNTY WILDLIFE LAKE DAM
ROWAN-005
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 Rowan County Wildlife Lake 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, and 200
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 =
789.4
613.1
640.4
668.6
697.7
727.5
758.1
741.6
742.1
742.6
743.1
743.6
ELEVATION
739.1
739.6
740.1
740.6
741.1
36.9
43.7
50.8
STORAGE (ACRE-FT)
0.0
4.3
9.1
14.1
19.3
24.7
30.5
723.1
720.1
720.6
721.1
721.6
722.1
722.6
718.6
723.5
ELEVATION
718.6
719.1
719.6
STORAGE (ACRE-FT)
535.7
560.7
586.5
66.1
67
SCS Type 2
SPILLWAY
Primary
Auxiliary
TYPE
Riser / Barrel
Grass Lined Trapezoidal Channel
ELEVATION
24 HOUR - 200 YEAR EVENT, 7.88 INCHES, ELEVATION 725 (0.3 FT FREE-BOARD)
24 HOUR - 100 YEAR EVENT, 7.13 INCHES, ELEVATION 724.6 (0.7 FT FREE-BOARD)
24 HOUR - 50 YEAR EVENT, 6.41 INCHES, ELEVATION 724.1 (1.2 FT FREE-BOARD)
24 HOUR - 25 YEAR EVENT, 5.69 INCHES, ELEVATION 723.2 (2.1 FT FREE-BOARD)
SUMMARY OF INPUT PARAMETERS
1.03
SUMMARY SHEET OF HYDRAULIC CAPACITY RESULTS
ROWAN COUNTY WILDLIFE LAKE DAM, ROWAN-005
ANALYSIS PERFORMED BY: S. MURPHY, HDR
24 HOUR - 1000 YEAR EVENT, 9.69 INCHES, ELEVATION 725.8 (0.5 FT OVER-TOPPED)
24 HOUR - 500 YEAR EVENT, 8.9 INCHES, ELEVATION 725.5 (0.2 FT OVER-TOPPED)
TOP OF DAM ELEVATION = 725.3
ROWAN-005ROWAN COUNTY WILDLIFE LAKE DAM NOVEMBER 23, 2020
2144.0
NOT TO SCALE
1800.1
1854.6
1910.2
1966.9
2024.7
2083.8
1496.4
1544.3
1593.3
1643.3
1694.5
1746.7
1228.5
1270.8
1314.1
1358.2
1403.3
1449.4
993.7
1030.7
1068.5
1107.2
1146.7
1187.1
821.4
854.2
887.8
922.3
957.5
756.6
757.1
757.6
758.1
758.6
753.6
754.1
754.6
755.1
755.6
756.1
750.6
751.1
751.6
752.1
752.6
753.1
747.6
748.1
748.6
749.1
749.6
750.1
744.6
745.1
745.6
746.1
746.6
747.1
744.1
442.8
465.1
487.9
511.5
322.7
341.2
360.3
380.0
400.3
421.2
223.3
238.5
254.2
270.5
287.3
304.7
144.5
156.2
168.5
181.2
194.6
208.6
83.5
92.7
102.2
112.1
122.5
133.2
58.4
66.4
74.8
738.1
738.6
735.1
735.6
736.1
736.6
737.1
737.6
732.1
732.6
733.1
733.6
734.1
734.6
729.1
729.6
730.1
730.6
731.1
731.6
726.1
726.6
727.1
727.6
728.1
728.6
723.6
724.1
724.6
725.1
725.6
ROWAN-005ROWAN COUNTY WILDLIFE LAKE DAM NOVEMBER 23, 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
Rowan County W ildlife Lake Dam - ROWAN-005 - Watershed Boundary
Legend
Longest FlowPath
Watershed Bound ary
0 0.4 0.80.2 Miles
Date: 11/19/2020
/Drainage Area: 1.03 Square MilesFlowpath Length: 1.8 Miles

APPENDIX B

Lag Time Calculation
Dam No:ROWAN-005 Date:11/18/2020
Dam Name:Rowan County Wildlife Lake 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 =66.1011 from NRCS CN Calculation
S =5.12834 in.
Mean Basin Slope Y =6.53846 %from Watershed Mean slope
Longest Flowpath:1.79 mi.from Watershed Longest flowpath
Flow Length l =9451.2 ft.
Time of Concentration Tc =1.85 Hours Tc =111 mins
Lag Time TL =1.11 Hours TL =67 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 72253 100 7225327 0 100 0 470140 100 47014007
Developed, Open Space Open space - Fair condition (grass cover 50% to 75%)0 49 0 4835495 69 333649179 161480 79 12756888 66828 84 5613580
Developed, Low Intensity Residential districts by average lot size: 1/3 acre 0 57 0 1636767 72 117847219 26557 81 2151118 29746 86 2558159
Developed, Medium Intensity Residential districts by average lot size: 1/8 acre 0 77 0 545669 85 46381834 164 90 14726 0 92 0
Developed, High Intensity Urban districts - Commercial and business 0 89 0 0 92 0 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 8297612 60 497856694 585144 73 42715541 341230 79 26957193
Evergreen Forest Woods - Fair 0 36 0 3903363 60 234201798 21111 73 1541084 27961 79 2208907
Mixed Forest Woods - Fair 0 36 0 2557787 60 153467198 147015 73 10732085 89923 79 7103954
Shrub/Scrub Brush - Fair 0 35 0 0 56 0 0 70 0 0 77 0
Herbaceuous Herbaceuous - Fair 0 60 0 235841 71 16744730 10621 81 860316 32172 89 2863339
Hay/Pasture Pasture - Fair 0 49 0 4157543 69 286870441 267429 79 21126874 16343 84 1372786
Cultivated Crops Row crops (SR + CR) - Poor 0 71 0 300254 80 24020296 0 87 0 0 90 0
Woody Wetlands Not Available 0 80 0 0 85 0 0 90 0 0 95 0
Emergent Herbaceuous Wetlands Not Available 0 80 0 1419 85 120647 0 90 0 8266 95 785290 Weighted CN=66.10
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): Salisbury, North Carolina USA
Station Name: -
Latitude: 35.698321°
Longitude: -80.544748°
Elevation (USGS): 767 ft
PRECIPITATION FREQUENCY ESTIMATES
by
duration
for ARI
(years):1 2 5 10 25 50 100 200 500 1000
5-min:0.382 0.453 0.529 0.582 0.642 0.682 0.719 0.75 0.784 0.807
10-min:0.611 0.724 0.847 0.931 1.02 1.09 1.14 1.19 1.24 1.27
15-min:0.763 0.91 1.07 1.18 1.3 1.38 1.44 1.5 1.56 1.6
30-min:1.05 1.26 1.52 1.71 1.92 2.07 2.21 2.34 2.48 2.58
60-min:1.31 1.58 1.95 2.22 2.56 2.81 3.05 3.28 3.56 3.77
2-hr:1.51 1.82 2.27 2.61 3.04 3.37 3.69 4 4.41 4.72
3-hr:1.61 1.94 2.43 2.79 3.28 3.66 4.03 4.41 4.91 5.29
6-hr:1.95 2.34 2.93 3.38 3.99 4.47 4.95 5.43 6.09 6.59
12-hr:2.29 2.76 3.46 4.01 4.76 5.36 5.97 6.6 7.46 8.12
24-hr:2.73 3.29 4.13 4.8 5.69 6.41 7.13 7.88 8.9 9.69
2-day:3.16 3.81 4.74 5.47 6.46 7.24 8.03 8.84 9.93 10.8
3-day:3.36 4.04 5.01 5.77 6.8 7.61 8.44 9.29 10.4 11.3
4-day:3.57 4.28 5.28 6.07 7.14 7.98 8.85 9.73 10.9 11.9
7-day:4.13 4.92 5.99 6.83 7.98 8.89 9.81 10.8 12 13
10-day:4.7 5.59 6.72 7.6 8.77 9.69 10.6 11.6 12.8 13.8
20-day:6.33 7.47 8.81 9.87 11.3 12.4 13.5 14.7 16.2 17.4
30-day:7.83 9.21 10.7 11.8 13.3 14.5 15.6 16.7 18.2 19.3
45-day:9.85 11.5 13.1 14.4 16 17.2 18.4 19.5 21 22.2
60-day:11.7 13.7 15.4 16.7 18.5 19.8 21 22.2 23.8 24.9
Date/time (GMT): Wed Nov 18 19:19:23 2020
pyRunTime: 0.0441660881042

APPENDIX F
Outlet Works Rating Curves

Total outlet discharge from the spillway system
Client:NCEM Date:11/17/2020
Project:Overtopping Study Engineer:T.Carter
Dam:Rowan County Wildlife Lake Dam Dam No.ROWAN-005
Reservior Water
Level (RWS)
Elevation (ft)
Primary spillway
discharge (cfs)
Emergency spillway
discharge (cfs)
Total discharge from the
spillway system (cfs)
718.6 0.0 0.0 0.0
719.1 21.9 0.0 21.9
719.6 62.0 0.0 62.0
720.1 111.3 0.0 111.3
720.6 113.9 0.0 113.9
721.1 116.4 0.0 116.4
721.6 118.9 0.0 118.9
722.1 121.3 0.0 121.3
722.6 123.7 0.0 123.7
723.1 126.0 0.0 126.0
723.6 128.3 4.0 132.3
724.1 130.5 64.6 195.1
724.6 132.7 174.8 307.5
725.1 134.9 331.9 466.8
725.6 137.0 537.1 674.1
726.1 139.1 792.4 931.4
726.6 141.2 1099.8 1241.0
727.1 143.2 1461.7 1604.9
727.6 145.2 1880.4 2025.6
728.1 147.2 2358.0 2505.1
728.6 149.1 2896.6 3045.8
729.1 151.1 3498.5 3649.6
729.6 153.0 4165.7 4318.7
730.1 154.9 4900.2 5055.0
730.6 156.7 5703.9 5860.6
731.1 158.5 6578.9 6737.4
731.6 160.4 7526.8 7687.2
732.1 162.2 8549.6 8711.8
732.6 163.9 9649.1 9813.0
733.1 165.7 10827.0 10992.7
733.6 167.4 12085.0 12252.4
734.1 169.2 13424.8 13594.0
734.6 170.9 14848.1 15018.9
735.1 172.5 16356.4 16528.9
735.6 174.2 17951.3 18125.6
736.1 175.9 19634.5 19810.4
736.6 177.5 21407.4 21584.9
737.1 179.1 23271.6 23450.7
737.6 180.7 25228.5 25409.2
738.1 182.3 27279.6 27461.9
738.6 183.9 29426.3 29610.3
739.1 185.5 31670.1 31855.6
739.6 187.0 34012.4 34199.4
740.1 188.6 36454.5 36643.1
740.6 190.1 38997.8 39187.9
741.1 191.6 41643.6 41835.2
741.6 193.1 44393.3 44586.4
742.1 194.6 47248.1 47442.8
742.6 196.1 50209.5 50405.6
743.1 197.6 53278.6 53476.1
743.6 199.0 56456.7 56655.7
744.1 200.5 59745.0 59945.5
0.0
10000.0
20000.0
30000.0
40000.0
50000.0
60000.0
70000.0
715.0 720.0 725.0 730.0 735.0 740.0 745.0 750.0Total discharge from the spillway system (cfs)Reservior Water Level (RWS) Elevation (ft)
The whole spillway system rating curve (cfs)