RANDO-025 Final Report

DAM HYDRAULIC CAPACITY
ASSESSMENT REPORT
(DRAFT)
JOHN BUNCH LAKE DAM
RANDO-025
RANDOLPH COUNTY, NC
PREPARED BY:
WOOD E&I Solutions
2020
EXECUTIVE SUMMARY
A hydraulic capacity analysis was completed for the John Bunch Lake Dam in Randolph 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 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, 8.23 INCHES, ELEVATION 536.1 (2.9 FT FREE‐BOARD)
24 HOUR ‐ 100 YEAR EVENT, 7.46 INCHES, ELEVATION 535.5 (3.5 FT FREE‐BOARD)
24 HOUR ‐ 50 YEAR EVENT, 6.71 INCHES, ELEVATION 534.8 (4.2 FT FREE‐BOARD)
24 HOUR ‐ 25 YEAR EVENT, 5.98 INCHES, ELEVATION 534.2 (4.8 FT FREE‐BOARD)
549.8
550
325.3
343.7
362.4
381.2
STORAGE (ACRE‐FT)
518.7
539.2
560.0
581.1
606.4
634.1
662.2
690.7
719.8
731.5
400.2
419.4
29.2
530.8
531.3
0.0
14.6
44.0
58.9
74.0
202.1
271.2
498.4
532.3
532.8
533.3
533.8
534.3
438.8
458.5
STORAGE (ACRE‐FT)
Auxiliary Grass‐Lined  Over‐flow embankment
531.8
539.0
540.8
541.3
SUMMARY SHEET OF HYDRAULIC CAPACITY RESULTS
JOHN BUNCH LAKE, RANDO‐025
SPILLWAY
ANALYSIS PERFORMED BY: E.OKORIE, WOOD
Principal Rectangular Concrete Chute spillway 530.8
SUMMARY OF INPUT PARAMETERS
SCS  Type 2
2.518
66.28
105
ELEVATIONTYPE
TOP OF DAM ELEVATION = 539
24 HOUR ‐ 1000 YEAR EVENT, 10.1 INCHES, ELEVATION 537.7 (1.3 FT FREE‐BOARD)
24 HOUR ‐ 500 YEAR EVENT, 9.28 INCHES, ELEVATION 537 (2.0 FT FREE‐BOARD)
89.2
104.6
544.8
547.3
547.8
548.3
548.8
549.3
ELEVATION ELEVATION
535.8
536.3
536.8
120.3
136.3
152.4
168.8
185.3
478.3
289.0
307.1
539.8
540.3
543.3
543.8
544.3
545.3
541.8
542.3
542.8
545.8
546.3
546.8
219.0
236.2
253.6
537.3
537.8
538.3
538.8
539.3
534.8
535.3
JOHN BUNCH LAKE RANDO‐025 AUGUST 14, 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 the
GIS User Community
John Bunch Lake Dam - RANDO-025 - Watershed Boundary
Legend
Longest FlowPath
Watershed Boundary
0 0.55 1.10.275 Miles
Date: 8/13/2020
/Drainage Area: 2.52 Square Miles
Flowpath Length: 4.77 Miles
APPENDIX B
Lag Time Calculation
Dam No: RANDO-025 Date: 7/15/2020
Dam Name: John Bunch Lake Engineer: E.Okorie
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 = 66.28
S =5.08751 in.
Mean Basin Slope Y = 12.57 %
Longest Flowpath: 4.769 mi.
Flow Length l =25180.3 ft.
Time of Concentration Tc =2.91 Hours Tc =174 mins
Lag Time TL =1.74 Hours TL =105 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 2135572 100 213557244 0 100 0 43970 100 4396959
Developed, Open Space Open space - Fair condition (grass cover 50% to 75%)0 49 0 11937498 69 823687331 61470 79 4856112 32117 84 2697809
Developed, Low Intensity Residential districts by average lot size: 1/3 acre 0 57 0 2650004 72 190800259 14500 81 1174513 7139 86 613989
Developed, Medium Intensity Residential districts by average lot size: 1/8 acre 0 77 0 648632 85 55133711 47230 90 4250691 0 92 0
Developed, High Intensity Urban districts - Commercial and business 0 89 0 827016 92 76085461 96929 94 9111347 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 27171652 60 1630299121 3581569 73 261454547 604783 79 47777854
Evergreen Forest Woods - Fair 0 36 0 1950371 60 117022289 138489 73 10109732 107282 79 8475242
Mixed Forest Woods - Fair 0 36 0 3782459 60 226947520 108486 73 7919467 151438 79 11963566
Shrub/Scrub Brush - Fair 0 35 0 3988941 56 223380683 564991 70 39549372 279200 77 21498383
Herbaceuous Herbaceuous - Fair 0 60 0 2205239 71 156571973 267764 81 21688922 37097 89 3301597
Hay/Pasture Pasture - Fair 0 49 0 5916281 69 408223409 69790 79 5513391 772998 84 64931839
Cultivated Crops Row crops (SR + CR) - Poor 0 71 0 0 80 0 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 0 85 0 0 90 0 0 95 0 Weighted CN=66.28
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
0.02.04.06.08.010.012.00123456789101112131415161718192021222324Cumulative Depth (in)Time (hrs)Hyetographs for 24-Hour SCS Type II Rainfall Distributions25YR50YR100YR200YR500YR1000YR
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): Asheboro, North Carolina USA
Station Name: ‐
Latitude: 35.7013°
Longitude: ‐79.8541°
Elevation (USGS): None None
PRECIPITATION FREQUENCY ESTIMATES
by 
duration 
for ARI 
(years):1 2 5 10 25 50 100 200 500 1000
5‐min: 0.401 0.476 0.553 0.605 0.662 0.699 0.731 0.757 0.783 0.8
10‐min: 0.641 0.761 0.885 0.967 1.06 1.11 1.16 1.2 1.24 1.26
15‐min: 0.801 0.956 1.12 1.22 1.34 1.41 1.47 1.52 1.56 1.58
30‐min: 1.1 1.32 1.59 1.77 1.98 2.12 2.25 2.36 2.48 2.56
60‐min: 1.37 1.66 2.04 2.31 2.64 2.88 3.1 3.31 3.56 3.74
2‐hr: 1.61 1.95 2.42 2.77 3.2 3.53 3.84 4.15 4.54 4.83
3‐hr: 1.72 2.09 2.6 2.98 3.47 3.84 4.21 4.58 5.06 5.42
6‐hr: 2.09 2.52 3.14 3.61 4.23 4.72 5.22 5.71 6.39 6.9
12‐hr: 2.48 2.99 3.74 4.34 5.14 5.78 6.45 7.14 8.09 8.85
24‐hr: 2.89 3.49 4.37 5.05 5.98 6.71 7.46 8.23 9.28 10.1
2‐day: 3.38 4.06 5.05 5.8 6.82 7.62 8.43 9.27 10.4 11.3
3‐day: 3.59 4.31 5.33 6.12 7.19 8.03 8.89 9.77 11 11.9
4‐day: 3.8 4.56 5.61 6.43 7.55 8.44 9.34 10.3 11.5 12.5
7‐day: 4.35 5.19 6.31 7.19 8.4 9.35 10.3 11.3 12.7 13.8
10‐day: 4.95 5.89 7.08 8 9.25 10.2 11.2 12.2 13.6 14.7
20‐day: 6.67 7.86 9.28 10.4 11.9 13.1 14.4 15.6 17.3 18.6
30‐day: 8.24 9.69 11.3 12.5 14.1 15.3 16.5 17.8 19.4 20.6
45‐day: 10.4 12.2 13.9 15.3 17.1 18.4 19.7 21 22.8 24.1
60‐day: 12.5 14.5 16.4 17.8 19.7 21.1 22.4 23.7 25.4 26.7
Date/time (GMT):  Mon Jun 22 16:18:39 2020
pyRunTime:  0.0121359825134
APPENDIX F
Outlet Works Rating Curves
Total outlet discharge from the spillway system
Client:Date: 7/16/2020
Project:Engineer: E.Okorie
Dam:
NCEM
Overtopping Study
John Bunch Lake Dam No. RANDO-025
Reservior Water
Level (RWS)
Elevation (ft)
Primary spillway
discharge (cfs)
Emergency spillway
discharge (cfs)
Total discharge from the
spillway system (cfs)
530.8 0.0 0.0 0.0
531.3 32.9 0.0 32.9
531.8 93.0 0.0 93.0
532.3 170.9 0.0 170.9
532.8 263.0 0.0 263.0
533.3 367.6 0.0 367.6
533.8 483.2 0.0 483.2
534.3 609.0 0.0 609.0
534.8 744.0 0.0 744.0
535.3 887.8 0.0 887.8
535.8 1039.8 0.0 1039.8
536.3 1199.6 0.0 1199.6
536.8 1366.8 0.0 1366.8
537.3 1541.2 0.0 1541.2
537.8 1722.4 0.0 1722.4
538.3 1910.2 0.0 1910.2
538.8 2104.3 0.0 2104.3
539.3 2304.7 0.0 2304.7
539.8 2511.0 0.0 2511.0
540.3 2723.1 0.0 2723.1
540.8 2940.9 0.0 2940.9
541.3 3164.2 0.0 3164.2
541.8 3392.9 0.0 3392.9
542.3 3626.9 0.0 3626.9
542.8 3865.9 0.0 3865.9
543.3 4110.1 0.0 4110.1
543.8 4359.1 0.0 4359.1
544.3 4613.0 0.0 4613.0
544.8 4871.6 0.0 4871.6
545.3 5134.9 0.0 5134.9
545.8 5402.8 0.0 5402.8
546.3 5675.2 0.0 5675.2
546.8 5952.0 0.0 5952.0
547.3 6233.2 0.0 6233.2
547.8 6518.6 0.0 6518.6
548.3 6808.3 0.0 6808.3
548.8 7102.2 0.0 7102.2
549.3 7400.2 0.0 7400.2
549.8 7702.2 0.0 7702.2
550.3 8008.2 0.0 8008.2
550.8 8318.2 0.0 8318.2
551.3 8632.0 0.0 8632.0
551.8 8949.8 0.0 8949.8
552.3 9271.3 0.0 9271.3
552.8 9596.6 0.0 9596.6
553.3 9925.6 0.0 9925.6
553.8 10258.3 0.0 10258.3
554.3 10594.6 0.0 10594.6
554.8 10934.5 0.0 10934.5
555.3 11278.0 0.0 11278.0
555.8 11625.0 0.0 11625.0
0.0
2000.0
4000.0
6000.0
8000.0
10000.0
12000.0
14000.0
525.0 530.0 535.0 540.0 545.0 550.0 555.0 560.0Total discharge from the spillway system (cfs)Reservior Water Level (RWS) Elevation (ft)
The whole spillway system rating curve (cfs)