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Home My WebLink About20070295 Ver 6_8.01 Culvert Hydrology_20191220HOLDING VILLAGE POST -DEVELOPMENT HYDROLOGY MARIA TORRES, El RAP19000 Culvert 10/29/2019 Assume: HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 HSG 'A' = 51.9% HSG'B'= 45.3% HSG'C'= 0.0% HSG'D'= 2.8% II. FUTURE -DEVELOPMENT r A. Zoning Breakdown* Contributing Area Area (sf) Max Density % ** Impervious Area sf Residential Mixed -Use 294,255 65 191,266 Neighborhood Mixed -Use 399,610 85 339,669 Urban Residential 0 65 0 Rural Holding District 0 20 0 Light Industrial 0 72 0 General Residential 3 0 30 0 General Residential 5 0 53 0 Nei hborhood Business 0 85 0 Totals 693,865 530,934 B. Watershed Land Use Breakdown Total area= 15.93 acres 693,865 sf Composite SCS CN = 87 % Impervious = 76.5% *Zoning areas were taken from the Town of Wake Forest current official **Max densities were taken from the Zoning Map and the TR-55 HOLDING VILLAGE RAP19000 C. Time of Concentration Information Time of concentration is calculated using the SCS Segmental Approach (TR-55). Segment 1: Overland Flow POST -DEVELOPMENT HYDROLOGY Culvert 1 Length = 100 ft Top Elev = 380.00 ft Bot Elev = 370.00 ft Height= 10 ft Slope = 0.1000 ft/ft Manning's n = 0.40 wooded/dense underbrush P (2-year/24-hour) = 3.45 inches (Wake Forest, NC) Segment Time = 10.86 minutes Segment 3: Channel Flow Length = 407 ft Top Elev 356.00 Bot Elev = 326.00 Height = 30 ft Slope = 0.0737 ft/ft Manning's n = 0.045 natural channel Flow Area = 1.00 sf (assume V x 1' channel) Wetted Perimeter = 3.00 If (assume V x 1' channel) Channel Velocity = 4.32 ft/sec Segment Time = 1.57 minutes Segment 5: Channel Flow Length = 190 ft Top Elev 310.00 Bot Elev = 302.20 Height = 7.8 ft Slope = 0.0411 ft/ft Manning's n = 0.045 natural channel Flow Area = 4.00 sf (assume 2' x 2' channel) Wetted Perimeter = 6.00 If (assume 2' x 2' channel) Channel Velocity = 5.12 ft/sec Segment Time = 0.62 minutes Segment 2: Concentrated Flow Length = 169 ft Top Elev = 370.00 ft Bot Elev = 356.00 ft Height= 14 ft Slope = 0.0827 ft/ft Paved ? = No Velocity= 4.64 ft/sec Segment Time = 0.61 minutes Segment 4: Pipe Flow Length = 266 ft Top Elev = 326.00 Bot Elev = 310.00 Height= 16 ft Slope = 0.0602 ft/ft Manning's n = 0.130 RCP pipe Pipe Diameter= 5.00 ft Flow Area = 19.63 sf Wetted Perimeter = 15.71 If (3.5 ft ID pipe) Channel Velocity= 3.26 ft/sec Segment Time = 1.36 minutes Time of Concentration = 15.02 minutes SCS Lag Time = 9.01 minutes (SCS Lag = 0.6* Tc) Time Increment = 2.61 minutes (=0.29*SCS Lag) MARIA TORRES, El 10/29/2019 HOLDING VILLAGE POST -DEVELOPMENT HYDROLOGY MARIA TORRES, El RAP19000 Culvert 10/29/2019 Assume: HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 HSG 'A' = 36.9% HSG'B'= 19.5% HSG'C'= 2.4% HSG'D'= 41.2% II. FUTURE -DEVELOPMENT r A. Zoning Breakdown* Contributing Area Area (sf) Max Density % ** Impervious Area sf Residential Mixed -Use 691,854 65 449,705 Neighborhood Mixed -Use 929,611 85 790,169 Urban Residential 0 65 0 Rural Holding District 638,559 20 127,712 Light Industrial 0 72 0 General Residential 3 459,815 30 137,945 General Residential 5 3,883 53 2,058 Nei hborhood Business 478,377 85 406,620 Totals 3,202,099 1,914,209 B. Watershed Land Use Breakdown 61 1,287,890 Total area = 73.51 3,202,099 Composite SCS CN = 83 %Impervious= 59.8% acres sf *Zoning areas were taken from the Town of Wake Forest current official **Max densities were taken from the Zoning Map and the TR-55 HOLDING VILLAGE POST -DEVELOPMENT HYDROLOGY RAP19000 Culvert 2 C. Time of Concentration Information Time of concentration is calculated using the SCS Segmental Approach (TR-55). Segment 1: Overland Flow Segment 2: Concentrated Flow Length = 100 ft Length = 396 ft Top Elev = 408.00 ft Top Elev = 396.00 ft Bot Elev = 396.00 ft Bot Elev = 376.00 ft Height= 12 ft Height= 20 ft Slope = 0.1200 ft/ft Slope = 0.0505 ft/ft Manning's n = 0.24 dense grasses Paved ? = No P (2-year/24-hour) = 3.45 inches (Wake Forest, NC) Velocity= 3.63 ft/sec Segment Time = 6.71 minutes Segment Time = 1.82 minutes Segment 3: Channel Flow Segment 4: Pipe Flow Length = 581 ft Length = 36 ft Top Elev 376.00 Top Elev 372.00 Bot Elev = 372.00 Bot Elev = 370.00 Height = 4 ft Height = 2 ft Slope = 0.0069 ft/ft Slope = 0.0556 ft/ft Manning's n = 0.030 roadside ditch -grass Manning's n = 0.024 CMP pipe Flow Area = 8.00 sf (assume 4' x 2' channel) Pipe Diameter= 2.00 ft Wetted Perimeter = 8.00 If (assume 4' x 2' channel) Flow Area = 3.14 sf Channel Velocity = 4.12 ft/sec Wetted Perimeter = 6.28 If (2 ft ID pipe) Segment Time 2.35 minutes Channel Velocity= 9.22 ft/sec Segment Time = 0.07 minutes Segment 5: Channel Flow Segment 6: Lake Length = 1045 ft *Segment 6 assumed to have segment time of 0 min. Top Elev 370.00 Bot Elev = 328.00 Height = 42 ft Slope = 0.0402 ft/ft Manning's n = 0.045 natural channel Flow Area = 2.00 sf (assume 2' x 1' channel) Wetted Perimeter = 4.00 If (assume 2' x 1' channel) Channel Velocity = 4.18 ft/sec Segment Time = 4.16 minutes Segment 7. Channel Flow Length = 230 ft Top Elev 328.00 Bot Elev = 296.57 Height = 31.43 ft Slope = 0.1367 ft/ft Manning's n = 0.045 natural channel Flow Area = 2.00 sf (assume 2' x 1' channel) Wetted Perimeter = 4.00 If (assume 2' x 1' channel) Channel Velocity= 7.71 ft/sec Segment Time = 0.50 minutes Time of Concentration = 15.61 minutes SCS Lag Time = 9.37 minutes (SCS Lag = 0.6* Tc) Time Increment = 2.72 minutes (=0.29*SCS Lag) MARIA TORRES, El 10/29/2019 HOLDING VILLAGE POST -DEVELOPMENT HYDROLOGY MARIA TORRES, El RAP19000 Culvert 10/29/2019 Assume: HSG Impervious Open Wooded A 98 39 30 B 98 61 55 C 98 74 70 D 98 80 77 HSG 'A' = 1.6% HSG'B'= 9.6% HSG'C'= 19.1% HSG'D'= 69.7% II. FUTURE -DEVELOPMENT r A. Zoning Breakdown* Contributing Area Area (sf) Max Density % ** Impervious Area sf Residential Mixed -Use 0 65 0 Neighborhood Mixed -Use 0 85 0 Urban Residential 103,138 65 67,040 Rural Holding District 0 20 0 Light Industrial 699,071 72 503,331 General Residential 3 0 30 0 General Residential 5 0 53 0 Nei hborhood Business 0 85 0 Totals 802,209 570,371 B. Watershed Land Use Breakdown Total area= 18.42 acres 802,209 sf Composite SCS CN = 92 % Impervious = 71.1% *Zoning areas were taken from the Town of Wake Forest current official **Max densities were taken from the Zoning Map and the TR-55 HOLDING VILLAGE POST -DEVELOPMENT HYDROLOGY RAP19000 Culvert 3 C. Time of Concentration Information Time of concentration is calculated using the SCS Segmental Approach (TR-55). Segment 1: Overland Flow Segment 2: Concentrated Flow Length = 100 ft Length = 572 ft Top Elev = 374.00 ft Top Elev = 368.00 ft Bot Elev = 368.00 ft Bot Elev = 326.00 ft Height= 6 ft Height= 42 ft Slope = 0.0600 ft/ft Slope = 0.0734 ft/ft Manning's n = 0.24 dense grasses Paved ? = No P (2-year/24-hour) = 3.45 inches (Wake Forest, NC) Velocity= 4.37 ft/sec Segment Time = 8.86 minutes Segment Time = 2.18 minutes Segment 3: Channel Flow Length = 486 ft Top Elev 326.00 Bot Elev = 307.36 Height = 18.64 ft Slope = 0.0383 ft/ft Manning's n = 0.030 roadside ditch -grass Flow Area = 1.00 sf (assume V x V channel) Wetted Perimeter = 3.00 If (assume V x 1' channel) Channel Velocity = 4.67 ft/sec Segment Time = 1.73 minutes Time of Concentration = 12.77 minutes SCS Lag Time = 7.66 minutes (SCS Lag = 0.6* Tc) Time Increment = 2.22 minutes (=0.29*SCS Lag) MARIA TORRES, El 10/29/2019