WILKE-050 Final Report

DAM HYDRAULIC CAPACITY
ASSESSMENT REPORT
(DRAFT)

BIG WARRIOR CREEK DAM

WILKE-050

WILKES 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 Big Warrior Creek Dam in Wilkes 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, 9.12 INCHES, ELEVATION 1204.9 (5.1 FT FREE-BOARD)
24 HOUR - 100 YEAR EVENT, 8.19 INCHES, ELEVATION 1204.2 (5.8 FT FREE-BOARD)
24 HOUR - 50 YEAR EVENT, 7.31 INCHES, ELEVATION 1203.5 (6.5 FT FREE-BOARD)
24 HOUR - 25 YEAR EVENT, 6.45 INCHES, ELEVATION 1202.9 (7.1 FT FREE-BOARD)
SUMMARY OF INPUT PARAMETERS
3.91
SUMMARY SHEET OF HYDRAULIC CAPACITY RESULTS
BIG WARRIOR CREEK DAM, WILKE-050
ANALYSIS PERFORMED BY: S. MURPHY, HDR
TOP OF DAM ELEVATION = 1210
24 HOUR - 1000 YEAR EVENT, 11.4 INCHES, ELEVATION 1206 (4 FT FREE-BOARD)
24 HOUR - 500 YEAR EVENT, 10.4 INCHES, ELEVATION 1205.6 (4.4 FT FREE-BOARD)
71.22
63
SCS Type 2
SPILLWAY
Primary
Auxiliary
TYPE
Riser / Barrel
Grass Lined Trapezoidal channel
ELEVATION
1201.5
1202.0
1202.5
1203.0
1203.5
1204.0
1200.0
1205.0
ELEVATION
1200.0
1200.5
1201.0
STORAGE (ACRE-FT)
3648.7
3759.6
3871.7
STORAGE (ACRE-FT)
0.0
69.9
140.6
212.1
284.2
357.2
431.1
1204.5
ELEVATION
1220.5
1221.0
1221.5
1222.0
1222.5
506.0
581.9
658.9
3984.9
4099.5
4215.4
4332.7
4451.4
4571.5
1223.0
1223.5
1224.0
1224.5
1225.0 4693.0
WILKE-050BIG WARRIOR CREEK DAM SEPTEMBER 10, 2020
1209.0
1209.5
1210.0
1205.0
1205.5
1206.0
1206.5
1207.0
1207.5
1208.0
1208.5
1216.5
1213.5
1214.0
1214.5
1215.0
1215.5
1216.0
1210.5
1211.0
1211.5
1212.0
1212.5
1213.0
2599.3
2699.3
2800.4
2021.9
2115.5
2210.1
2305.8
2402.5
2500.3
1482.2
1569.6
1658.0
1747.4
1837.9
1929.4
977.5
1059.5
1142.3
3322.6
3430.2
2902.7
3006.1
3110.6
1225.9
1310.4
1395.8
737.1
816.3
896.4
5447.6
5577.7
1225.5
1235.0
1235.5
1236.0
1236.5
1237.0
1237.5
1226.0
1226.5
1227.0
1227.5
1228.0
1228.5
1230.5
1231.0
1231.5
1232.0
1232.5
1233.0
1233.5
1234.0
1234.5
1229.0
1229.5
1230.0
5709.1
5841.8
5975.8
6111.1
4815.6
4939.6
5064.7
5191.1
5318.7
7095.7
7242.0
7389.6
7538.6
7689.2
7841.2
6247.7
6385.7
6525.0
6665.6
6807.6
6951.0
8946.6
NOT TO SCALE
7994.8
8149.9
8306.5
8464.4
8623.7
8784.51239.5
1240.0
3538.9
1219.5
1220.0
1217.0
1217.5
1218.0
1218.5
1219.0
1238.0
1238.5
1239.03216.1
WILKE-050BIG WARRIOR CREEK 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
Big Warrior Creek Dam - WILKE-050 - Watershed Boundary
Legend
LongestFlowPath
WatershedBoundary
0 0.6 1.20.3 Miles
Date: 8/31/2020
/Drainage Area: 3.91 Square MilesFlowpath Length: 25280.5 feet

APPENDIX B
Lag Time Calculation

Dam No:WILKE-050 Date:9/4/2020
Dam Name:Big Warrior Creek 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 =71.2235 from NRCS CN Calculation
S =4.04031 in.
Mean Basin Slope Y =26.938 %from Watershed Mean slope
Longest Flowpath:4.78797 mi.from Watershed Longest flowpath
Flow Length l =25280.5 ft.
Time of Concentration Tc =1.75 Hours Tc =105 mins
Lag Time TL =1.05 Hours TL =63 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 1800807 100 180080743 1478204 100 147820361 2089531 100 208953138
Developed, Open Space Open space - Fair condition (grass cover 50% to 75%)0 49 0 1461050 69 100812446 10850 79 857162 295477 84 24820042
Developed, Low Intensity Residential districts by average lot size: 1/3 acre 0 57 0 131469 72 9465783 1777 81 143951 38228 86 3287644
Developed, Medium Intensity Residential districts by average lot size: 1/8 acre 0 77 0 19633 85 1668836 0 90 0 9427 92 867281
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 121274 86 10429598 51211 91 4660235 59998 94 5639859
Deciduous Forest Woods - Fair 1166265 36 41985532 23747256 60 1424835378 8553881 73 624433281 18988630 79 #########
Evergreen Forest Woods - Fair 0 36 0 1648236 60 98894170 246755 73 18013100 716817 79 56628517
Mixed Forest Woods - Fair 444528 36 16002998 11070817 60 664249045 8528207 73 622559118 10232649 79 808379237
Shrub/Scrub Brush - Fair 0 35 0 245644 56 13756065 0 70 0 311836 77 24011352
Herbaceuous Herbaceuous - Fair 1414 60 84817 514985 71 36563932 5641 81 456946 180482 89 16062911
Hay/Pasture Pasture - Fair 401012 49 19649571 8869294 69 611981272 1126950 79 89029047 2404927 84 202013881
Cultivated Crops Row crops (SR + CR) - Poor 0 71 0 711007 80 56880595 782575 87 68084058 79746 90 7177122
Woody Wetlands Not Available 0 80 0 119053 85 10119509 0 90 0 345915 95 32861881
Emergent Herbaceuous Wetlands Not Available 0 80 0 0 85 0 0 90 0 0 95 0 Weighted CN=71.22
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): Boomer, North Carolina USA
Station Name: -
Latitude: 36.0433°
Longitude: -81.2857°
Elevation (USGS): 1208.82 ft
PRECIPITATION FREQUENCY ESTIMATES
by
duration
for ARI
(years):1 2 5 10 25 50 100 200 500 1000
5-min:0.359 0.426 0.506 0.57 0.654 0.718 0.785 0.853 0.946 1.02
10-min:0.573 0.682 0.81 0.912 1.04 1.14 1.25 1.35 1.5 1.61
15-min:0.716 0.857 1.02 1.15 1.32 1.45 1.58 1.71 1.88 2.02
30-min:0.982 1.18 1.46 1.67 1.96 2.18 2.42 2.66 3 3.27
60-min:1.22 1.49 1.87 2.18 2.61 2.96 3.33 3.73 4.3 4.77
2-hr:1.43 1.74 2.21 2.58 3.13 3.59 4.08 4.61 5.4 6.06
3-hr:1.55 1.88 2.37 2.78 3.37 3.87 4.42 5.01 5.89 6.64
6-hr:1.95 2.36 2.96 3.44 4.14 4.73 5.35 6.03 7.01 7.83
12-hr:2.47 2.98 3.7 4.26 5.04 5.67 6.32 7 7.95 8.72
24-hr:3.03 3.67 4.63 5.39 6.45 7.31 8.19 9.12 10.4 11.4
2-day:3.62 4.37 5.49 6.37 7.6 8.59 9.62 10.7 12.2 13.4
3-day:3.86 4.65 5.81 6.72 7.98 8.99 10 11.1 12.6 13.8
4-day:4.1 4.94 6.14 7.08 8.36 9.38 10.4 11.5 13 14.2
7-day:4.72 5.65 6.9 7.87 9.16 10.2 11.2 12.3 13.7 14.8
10-day:5.4 6.44 7.75 8.75 10.1 11.1 12.1 13.1 14.5 15.6
20-day:7.2 8.53 10.1 11.3 12.9 14.1 15.4 16.6 18.3 19.6
30-day:8.93 10.5 12.1 13.4 14.9 16.1 17.2 18.3 19.8 20.8
45-day:11.3 13.2 15 16.3 17.9 19.2 20.4 21.6 23 24.2
60-day:13.4 15.7 17.6 19.1 20.9 22.3 23.7 24.9 26.6 27.8
Date/time (GMT): Fri Aug 28 16:04:02 2020
pyRunTime: 0.0159268379211

APPENDIX F
Outlet Works Rating Curves

Total outlet discharge from the spillway system
Client:NCEM Date:9/4/2020
Project:Overtopping Study Engineer:K.Trefzger
Dam:Big Warrior Creek Dam Dam No.WILKE-050
Reservior Water
Level (RWS)
Elevation (ft)
Primary spillway
discharge (cfs)
Emergency spillway
discharge (cfs)
Total discharge from the
spillway system (cfs)
1200.0 0.0 0.0 0.0
1200.5 31.0 0.0 31.0
1201.0 87.7 0.0 87.7
1201.5 161.0 0.0 161.0
1202.0 247.9 0.0 247.9
1202.5 346.5 0.0 346.5
1203.0 455.4 0.0 455.4
1203.5 573.1 0.0 573.1
1204.0 612.6 0.0 612.6
1204.5 649.8 0.0 649.8
1205.0 684.9 0.0 684.9
1205.5 718.4 398.5 1116.8
1206.0 750.3 1132.0 1882.3
1206.5 781.0 2088.8 2869.8
1207.0 810.4 3230.1 4040.5
1207.5 838.9 4533.9 5372.8
1208.0 866.4 5986.0 6852.4
1208.5 893.1 7575.9 8469.0
1209.0 918.9 9296.0 10214.9
1209.5 944.1 11140.1 12084.2
1210.0 968.7 13103.4 14072.0
1210.5 992.6 15181.7 16174.3
1211.0 1015.9 17371.8 18387.7
1211.5 1038.8 19670.7 20709.5
1212.0 1061.1 22076.1 23137.3
1212.5 1083.0 24585.9 25668.9
1213.0 1104.4 27198.2 28302.6
1213.5 1125.5 29911.3 31036.8
1214.0 1146.1 32724.0 33870.1
1214.5 1166.4 35634.9 36801.4
1215.0 1186.1 38643.0 39829.1
0.0
5000.0
10000.0
15000.0
20000.0
25000.0
30000.0
35000.0
40000.0
45000.0
1198.0 1200.0 1202.0 1204.0 1206.0 1208.0 1210.0 1212.0 1214.0 1216.0Total discharge from the spillway system (cfs)Reservior Water Level (RWS) Elevation (ft)
The whole spillway system rating curve (cfs)