ROWAN-063 Final Report

DAM HYDRAULIC CAPACITY
ASSESSMENT REPORT
(DRAFT)

SALISBURY COMMUNITY PARK DAM

ROWAN-063

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 Salisbury Community Park 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, 7.88 INCHES, ELEVATION 777.7 (2.3 FT FREE-BOARD)
24 HOUR - 100 YEAR EVENT, 7.13 INCHES, ELEVATION 777.5 (2.5 FT FREE-BOARD)
24 HOUR - 50 YEAR EVENT, 6.4 INCHES, ELEVATION 777.2 (2.8 FT FREE-BOARD)
24 HOUR - 25 YEAR EVENT, 5.69 INCHES, ELEVATION 777 (3 FT FREE-BOARD)
SUMMARY OF INPUT PARAMETERS
0.15
SUMMARY SHEET OF HYDRAULIC CAPACITY RESULTS
SALISBURY COMMUNITY PARK DAM, ROWAN-063
ANALYSIS PERFORMED BY: S. MURPHY, HDR
TOP OF DAM ELEVATION = 780
24 HOUR - 1000 YEAR EVENT, 9.69 INCHES, ELEVATION 778.2 (1.8 FT FREE-BOARD)
24 HOUR - 500 YEAR EVENT, 8.89 INCHES, ELEVATION 778 (2 FT FREE-BOARD)
69.19
33
SCS Type 2
SPILLWAY
Primary
Auxiliary
TYPE
Riser / Barrel
Riprap Lined Trapezoidal channel
ELEVATION
777.5
778.0
778.5
779.0
779.5
780.0
776.0
777.6
ELEVATION
776.0
776.5
777.0
STORAGE (ACRE-FT)
287.9
298.9
310.2
STORAGE (ACRE-FT)
0.0
4.1
8.2
12.5
17.0
21.5
26.2
780.5
ELEVATION
796.5
797.0
797.5
798.0
798.5
31.1
36.1
41.3
321.6
333.4
345.3
357.6
370.1
382.8
799.0
799.5
800.0
800.5
801.0 395.9
ROWAN-063SALISBURY COMMUNITY PARK DAM SEPTEMBER 10, 2020
785.0
785.5
786.0
781.0
781.5
782.0
782.5
783.0
783.5
784.0
784.5
792.5
789.5
790.0
790.5
791.0
791.5
792.0
786.5
787.0
787.5
788.0
788.5
789.0
190.8
199.5
208.5
142.6
150.2
158.0
165.9
174.0
182.3
100.3
107.0
113.8
120.8
127.9
135.1
63.3
69.2
75.1
256.4
266.7
217.6
227.0
236.6
81.2
87.4
93.8
46.6
52.0
57.6
480.1
495.2
801.5
811.0
811.5
812.0
812.5
813.0
813.5
802.0
802.5
803.0
803.5
804.0
804.5
806.5
807.0
807.5
808.0
808.5
809.0
809.5
810.0
810.5
805.0
805.5
806.0
510.6
526.2
542.2
558.5
409.2
422.8
436.7
450.9
465.4
684.4
704.3
724.6
745.4
766.5
788.1
575.1
592.1
609.6
627.5
646.0
665.0
953.5
NOT TO SCALE
810.2
832.8
855.8
879.4
903.6
928.3815.5
816.0
277.2
795.5
796.0
793.0
793.5
794.0
794.5
795.0
814.0
814.5
815.0246.4
ROWAN-063SALISBURY COMMUNITY PARK 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
Salisbury Community Park Dam - ROWAN-063 - Watershed Boundary
Legend
LongestFlowPath
WatershedBoundary
0 0.15 0.30.075 Miles
Date: 8/31/2020
/Drainage Area: 0.15 Square MilesFlowpath Length: 4108.5 feet

APPENDIX B
Lag Time Calculation

Dam No:ROWAN-063 Date:9/4/2020
Dam Name:Salisbury Community Park 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 =69.1905 from NRCS CN Calculation
S =4.45285 in.
Mean Basin Slope Y =5.80101 %from Watershed Mean slope
Longest Flowpath:0.77813 mi.from Watershed Longest flowpath
Flow Length l =4108.53 ft.
Time of Concentration Tc =0.93 Hours Tc =56 mins
Lag Time TL =0.56 Hours TL =33 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 32291 100 3229068 0 100 0 200164 100 20016384
Developed, Open Space Open space - Fair condition (grass cover 50% to 75%)0 49 0 233226 69 16092582 5899 79 466025 0 84 0
Developed, Low Intensity Residential districts by average lot size: 1/3 acre 0 57 0 95433 72 6871188 0 81 0 0 86 0
Developed, Medium Intensity Residential districts by average lot size: 1/8 acre 0 77 0 63338 85 5383722 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 0 86 0 0 91 0 0 94 0
Deciduous Forest Woods - Fair 0 36 0 1164041 60 69842461 70765 73 5165879 28775 79 2273207
Evergreen Forest Woods - Fair 0 36 0 83132 60 4987903 0 73 0 0 79 0
Mixed Forest Woods - Fair 0 36 0 2810 60 168571 0 73 0 0 79 0
Shrub/Scrub Brush - Fair 0 35 0 0 56 0 0 70 0 0 77 0
Herbaceuous Herbaceuous - Fair 0 60 0 11130 71 790248 0 81 0 8241 89 733446
Hay/Pasture Pasture - Fair 0 49 0 1864026 69 128617789 27646 79 2184067 16343 84 1372786
Cultivated Crops Row crops (SR + CR) - Poor 0 71 0 177076 80 14166091 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 120646 0 90 0 8266 95 785293 Weighted CN=69.19
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: 35.6970999999999°
Longitude: -80.5485°
Elevation (USGS): 779.01 ft
PRECIPITATION FREQUENCY ESTIMATES
by
duration
for ARI
(years):1 2 5 10 25 50 100 200 500 1000
5-min:0.383 0.453 0.529 0.582 0.642 0.683 0.719 0.75 0.785 0.808
10-min:0.611 0.724 0.847 0.931 1.02 1.09 1.14 1.19 1.24 1.27
15-min:0.764 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 2.49 2.59
60-min:1.31 1.58 1.95 2.22 2.56 2.81 3.05 3.28 3.57 3.78
2-hr:1.51 1.83 2.27 2.61 3.04 3.37 3.69 4.01 4.42 4.72
3-hr:1.61 1.94 2.43 2.8 3.28 3.66 4.04 4.41 4.92 5.3
6-hr:1.95 2.35 2.93 3.39 3.99 4.47 4.95 5.44 6.1 6.6
12-hr:2.29 2.76 3.46 4.02 4.77 5.37 5.98 6.61 7.47 8.13
24-hr:2.73 3.29 4.13 4.79 5.69 6.4 7.13 7.88 8.89 9.69
2-day:3.16 3.8 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 9.28 10.4 11.3
4-day:3.57 4.28 5.28 6.06 7.14 7.98 8.85 9.73 10.9 11.9
7-day:4.12 4.92 5.98 6.83 7.97 8.88 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:9.86 11.5 13.2 14.4 16 17.2 18.4 19.5 21 22.2
60-day:11.7 13.7 15.4 16.8 18.5 19.8 21 22.2 23.8 24.9
Date/time (GMT): Fri Aug 28 16:04:00 2020
pyRunTime: 0.0256578922272

APPENDIX F
Outlet Works Rating Curves

Total outlet discharge from the spillway system
Client:NCEM Date:9/8/2020
Project:Overtopping Study Engineer:K.Trefzger
Dam:Salisbury Community Park Dam Dam No.ROWAN-063
Reservior Water
Level (RWS)
Elevation (ft)
Primary spillway
discharge (cfs)
Emergency spillway
discharge (cfs)
Total discharge from the
spillway system (cfs)
776.0 0.0 0.0 0.0
776.5 13.8 0.0 13.8
777.0 39.0 0.0 39.0
777.5 63.0 0.0 63.0
778.0 72.7 23.3 96.0
778.5 77.6 80.7 158.2
779.0 78.3 160.7 239.0
779.5 79.0 260.6 339.6
780.0 79.7 379.2 459.0
780.5 80.4 516.1 596.5
781.0 81.1 670.8 751.9
781.5 81.8 843.4 925.2
782.0 82.5 1033.7 1116.2
782.5 83.2 1241.9 1325.1
783.0 83.9 1468.2 1552.1
783.5 84.6 1712.6 1797.1
784.0 85.2 1975.3 2060.5
784.5 85.9 2256.5 2342.4
785.0 86.5 2556.5 2643.1
0.0
500.0
1000.0
1500.0
2000.0
2500.0
3000.0
775.0 776.0 777.0 778.0 779.0 780.0 781.0 782.0 783.0 784.0 785.0 786.0Total discharge from the spillway system (cfs)Reservior Water Level (RWS) Elevation (ft)
The whole spillway system rating curve (cfs)