YADKI-066 Final Report

DAM HYDRAULIC CAPACITY
ASSESSMENT REPORT
(DRAFT)
YADKINVILLE WTP RESERVOIR DAM
YADKI-066
YADKIN COUNTY, NC
PREPARED BY:
WOOD E&I Solutions
2020

EXECUTIVE SUMMARY
A hydraulic capacity analysis was completed for the Yadkinville WTP Reservoir Dam in Yadkin
County, North Carolina. The purpose of the study was to analyze the existing potential of the dam
for overtopping during predetermined specified rainfall events. 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 the structure is hydraulically adequate for the 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 =
113.7
118.9
124.2
NOT TO SCALE
84.0
88.8
93.7
98.6
103.6
108.6
819.0
819.5
820.0
STORAGE (ACRE‐FT)
60.9
65.4
70.0
74.6
79.3
816.0
816.5
817.0
817.5
818.0
818.5
ELEVATION
813.5
814.0
814.5
815.0
815.5
34.8
39.0
43.3
47.7
52.0
56.5
11.0
14.8
18.6
22.5
26.5
30.6
810.5
811.0
811.5
812.0
812.5
813
807.5
808.0
808.5
809.0
809.5
810.0
796
806.5
ELEVATION
806.0
806.5
807.0
STORAGE (ACRE‐FT)
0.0
3.6
7.3
72.75
18
SCS Type 2
SPILLWAY
Principal
Auxiliary
TYPE
7.0' x 7.0' Riser w/ 12"DIP Barrel
Concrete Trapezoidal Channel
ELEVATION
24 HOUR ‐ 200 YEAR EVENT, 8.54 INCHES, ELEVATION 806.3 (3.7 FT FREE‐BOARD)
24 HOUR ‐ 100 YEAR EVENT, 7.68 INCHES, ELEVATION 806.2 (3.8 FT FREE‐BOARD)
24 HOUR ‐ 50 YEAR EVENT, 6.85 INCHES, ELEVATION 806.2 (3.8 FT FREE‐BOARD)
24 HOUR ‐ 25 YEAR EVENT, 6.05 INCHES, ELEVATION 806.1 (3.9 FT FREE‐BOARD)
SUMMARY OF INPUT PARAMETERS
0.06
SUMMARY SHEET OF HYDRAULIC CAPACITY RESULTS
YADKINVILLE WTP RESERVOIR DAM, YADKI‐066
ANALYSIS PERFORMED BY: SURBHI THAKUR, WOOD
TOP OF DAM ELEVATION = 810
24 HOUR ‐ 1000 YEAR EVENT, 10.7 INCHES, ELEVATION 806.4 (3.6 FT FREE‐BOARD)
24 HOUR ‐ 500 YEAR EVENT, 9.72 INCHES, ELEVATION 806.3 (3.7 FT FREE‐BOARD)
YADKINVILLE WTP RESERVOIR DAM YADKI‐066 SEPTEMBER 18, 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
Yadkinville WTP Reservoir- YADKI-035 - Watershed Boundary
Legend
Longe st Flo wpath
Wa tershe d
0 0.1 0.20.05 Miles
Date : 9/10/2020
/Drainage Area: 0.06 Square MilesFlowpath Length: 3128 Feet

APPENDIX B
Lag Time Calculation

Dam No:Yadki-066 Date:
Dam Name:Engineer:S. Thakur
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 =72.75
S =3.7457 in.
Mean Basin Slope Y =10.8779 %
Longest Flowpath:0.59259 mi.
Flow Length l =3128.86 ft.
Time of Concentration Tc =0.49 Hours Tc =30 mins
Lag Time TL =0.30 Hours TL =18 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 145307 100 14530707 0 100 0 0 100 0
Developed, Open Space Open space - Fair condition (grass cover 50% to 75%)0 49 0 16393 69 1131136 3514 79 277617 0 84 0
Developed, Low Intensity Residential districts by average lot size: 1/3 acre 0 57 0 39428 72 2838821 2160 81 174945 0 86 0
Developed, Medium Intensity Residential districts by average lot size: 1/8 acre 0 77 0 0 85 0 0 90 0 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 9687 86 833095 0 91 0 0 94 0
Deciduous Forest Woods - Fair 0 36 0 257179 60 15430722 25410 73 1854905 20684 79 1634023
Evergreen Forest Woods - Fair 0 36 0 58123 60 3487372 0 73 0 0 79 0
Mixed Forest Woods - Fair 0 36 0 70105 60 4206307 26766 73 1953944 0 79 0
Shrub/Scrub Brush - Fair 0 35 0 29061 56 1627441 0 70 0 0 77 0
Herbaceuous Herbaceuous - Fair 0 60 0 0 71 0 0 81 0 0 89 0
Hay/Pasture Pasture - Fair 0 49 0 453605 69 31298773 121778 79 9620444 24350 84 2045420
Cultivated Crops Row crops (SR + CR) - Poor 0 71 0 250537 80 20042925 393 87 34151 4119 90 370706
Woody Wetlands Not Available 0 80 0 0 85 0 0 90 0 0 95 0
Emergent Herbaceuous Wetlands Not Available 0 80 0 0 85 0 0 90 0 0 95 0 Weighted CN=72.75
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 Analyses
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): Yadkinville, North Carolina USA
Station Name: -
Latitude: 36.1018°
Longitude: -80.6467°
Elevation (USGS): None None
PRECIPITATION FREQUENCY ESTIMATES
by
duration
for ARI
(years):1 2 5 10 25 50 100 200 500 1000
5-min:0.358 0.424 0.5 0.555 0.62 0.665 0.707 0.746 0.791 0.824
10-min:0.572 0.678 0.801 0.887 0.988 1.06 1.12 1.18 1.25 1.3
15-min:0.715 0.852 1.01 1.12 1.25 1.34 1.42 1.49 1.58 1.63
30-min:0.98 1.18 1.44 1.63 1.85 2.02 2.17 2.32 2.51 2.64
60-min:1.22 1.48 1.85 2.12 2.47 2.74 3 3.26 3.6 3.85
2-hr:1.44 1.75 2.2 2.54 3 3.35 3.71 4.07 4.56 4.93
3-hr:1.55 1.88 2.37 2.75 3.26 3.67 4.08 4.5 5.08 5.53
6-hr:1.91 2.31 2.91 3.38 4.02 4.53 5.05 5.59 6.34 6.92
12-hr:2.32 2.81 3.54 4.12 4.91 5.55 6.21 6.89 7.85 8.6
24-hr:2.83 3.43 4.34 5.06 6.05 6.85 7.68 8.54 9.72 10.7
2-day:3.33 4.02 5.04 5.84 6.92 7.77 8.64 9.54 10.8 11.7
3-day:3.55 4.27 5.33 6.15 7.27 8.15 9.06 9.98 11.3 12.3
4-day:3.76 4.52 5.61 6.46 7.62 8.53 9.47 10.4 11.7 12.8
7-day:4.3 5.14 6.27 7.15 8.32 9.24 10.2 11.1 12.4 13.4
10-day:4.92 5.87 7.06 7.98 9.19 10.1 11.1 12 13.3 14.3
20-day:6.6 7.82 9.25 10.4 11.8 13 14.1 15.3 16.8 18
30-day:8.2 9.65 11.1 12.3 13.7 14.8 15.8 16.8 18.1 19.1
45-day:10.3 12.1 13.7 15 16.5 17.7 18.8 19.8 21.2 22.2
60-day:12.3 14.4 16.2 17.5 19.2 20.5 21.7 22.8 24.3 25.4
Date/time (GMT): Tue Jun 23 12:00:57 2020
pyRunTime: 0.0161781311035

APPENDIX F
Outlet Works Rating Curves

Total outlet discharge from the spillway systemClient: NCFMPDate: 9/10/2020Project: Overtopping StudyEngineer: S. ThakurDam: Dutchman Creek #17 Dam No. YADKI-066Reservior Water Level (RWS) Elevation (ft)Primary spillway discharge (cfs)Emergency spillway discharge (cfs)Total discharge from the spillway system (cfs)806.0 0.0 0.0 0.0806.3 158.1 0.0 158.1806.6 159.4 3.5 162.9806.9 160.8 28.1 188.8807.2 162.1 64.9 227.0807.5 163.5 110.5 274.0807.8 164.8 163.5 328.3808.1 166.1 222.9 389.0808.4 167.4 287.9 455.3808.7 168.6 358.1 526.7809.0 169.9 433.0 602.9809.3 171.1 512.3 683.5809.6 172.4 595.8 768.2809.9 173.6 683.1 856.7810.2 174.8 774.1 948.9810.5 176.1 868.5 1044.6810.8 177.3 966.3 1143.5811.1 178.4 1067.2 1245.7811.4 179.6 1171.2 1350.8811.7 180.8 1278.0 1458.8812.0 182.0 1387.7 1569.6812.3 183.1 1500.0 1683.1812.6 184.3 1614.9 1799.2812.9 185.4 1732.3 1917.7813.2 186.5 1852.2 2038.7813.5 187.7 1974.3 2162.0813.8 188.8 2098.7 2287.5814.1 189.9 2225.3 2415.2814.4 191.0 2354.0 2544.9814.7 192.1 2484.7 2676.8815.0 193.2 2617.5 2810.6815.3 194.2 2752.1 2946.4815.6 195.3 2888.7 3084.0815.9 196.4 3027.0 3223.4816.2 197.4 3167.2 3364.6816.5 198.5 3309.0 3507.5816.8 199.5 3452.5 3652.1817.1 200.6 3597.7 3798.3817.4 201.6 3744.5 3946.1817.7 202.6 3892.7 4095.4818.0 203.7 4042.5 4246.2818.3 204.7 4193.8 4398.5818.6 205.7 4346.5 4552.2818.9 206.7 4500.6 4707.3819.2 207.7 4656.0 4863.7819.5 208.7 4812.7 5021.4819.8209.67 4970.785180.50.01000.02000.03000.04000.05000.06000.0804.0 806.0 808.0 810.0 812.0 814.0 816.0 818.0 820.0 822.0Total discharge from the spillway system (cfs)Reservior Water Level (RWS) Elevation (ft)The Whole Spillway System Rating Curve (cfs)