Volume 2-05, Chapter 3 - City of Wichita
Volume 2-05, Chapter 3 - City of Wichita Volume 2-05, Chapter 3 - City of Wichita
Section 3.2.5 - Enhanced Swale Step 8 Step 9 Design inlets, sediment forebay, and underdrain system. See Chapter 4 and Chapter 5 for more details. Prepare Vegetation and Landscaping Plan. A landscaping plan for an enhanced swale should be prepared to indicate how the enhanced swale system will be stabilized and established with vegetation. 3.2.5.7 Design Example Basic Data Small commercial lot 300 feet deep x 145 feet wide. • Drainage area (A) = 1.0 acres • Rainfall (P) = 1.2 inches (water quality event) • Runoff coefficient (R v ) = 0.70 Water Quality Peak Flow Compute the Water Quality Protection Volume in inches over the drainage area: WQ v = v P * R = 1.2*0.70 = 0.84inches Compute the Water Quality Peak Flow (see the grassed swale example for detailed calculations). Q wq 1.0 = 940csm ac * * 0.84in = 1.23 cfs in 640 ac 2 mi Pre-treatment Volume (Forebay) Compute the size of the sediment forebay (assume 80% of site is impervious) V pre = ( 0.80)(0.1")(1' /12") = 1.2*0.70 = 0.0067acre- ft Enhanced Swale Design Determine the swale dimensions (assume trapezoidal channel with max depth of 18 inches). The Q wq will be utilized to size the channel. The maximum flow depth of 4 inches is allowed for water quality design. A maximum flow velocity of 1.0 foot per second for water quality treatment is required. For Manning’s n use 0.15 for medium grass, 0.25 for dense grass, and 0.35 for very dense Bermuda-type grass. Input variables: n = 0.15 D = 1’ Page 3 - 76 Volume 2, Technical Guidance
Section 3.2.5 - Enhanced Swale Side Slopes = 2:1 Channel Slope = 0.015 ft/ft Then: 1.49 2 1 3 2 Q wq = Q = VA = D S DW n where: Q = peak flow (cfs) V = velocity (ft/sec) A = flow area (ft 2 ) = WD W = channel bottom width (ft) D = flow depth (ft) S = slope (ft/ft) A minimum width can be calculated. nQ 0.15*1.23 W = = 1 5 1 3 2 3 2 1.49D S 1.49*1 *0.015 5 = Q 1.23 V = = = 1.23 fps ( > 1fps) WD (1')(1') 1ft Increase width to 4’. Q 1.23 V = = = 0.31fps (OK) WD (4')(1') Check Dams Compute the number of check dams required to detain the WQ v . With where: • Dam height = 1.5 feet • Spacing of check dams will be 60 feet (based on top of downstream dam same elevation as upstream dam’s toe). The total volume need to be storage behind dams equals: WQ v = ( 0.84inches)(1acre) = 3050ft 3 Each dam stores: Volume = (length behind dam)(width of dam)(water depth behind dam) = (60’)(1.5’)(4’) = 360 ft 3 A total of (3050)/(360) = 8 check dams will be needed to capture the water quality volume. Volume 2, Technical Guidance Page 3 - 77
- Page 31 and 32: Section 3.2.1 - Stormwater Pond 3.2
- Page 33 and 34: Section 3.2.1 - Stormwater Pond Fig
- Page 35 and 36: Section 3.2.1 - Stormwater Pond For
- Page 37 and 38: Section 3.2.1 - Stormwater Pond •
- Page 39 and 40: Section 3.2.1 - Stormwater Pond 1'
- Page 41 and 42: Section 3.2.1 - Stormwater Pond •
- Page 43 and 44: Section 3.2.1 - Stormwater Pond •
- Page 45 and 46: Section 3.2.1 - Stormwater Pond 3.2
- Page 47 and 48: Section 3.2.1 - Stormwater Pond Ste
- Page 49 and 50: Section 3.2.1 - Stormwater Pond Fig
- Page 51 and 52: Section 3.2.1 - Stormwater Pond Fig
- Page 53 and 54: Section 3.2.2 - Extended Dry Detent
- Page 55 and 56: Section 3.2.2 - Extended Dry Detent
- Page 57 and 58: Section 3.2.2 - Extended Dry Detent
- Page 59 and 60: Section 3.2.3 - Vegetative Filter S
- Page 61 and 62: Section 3.2.3 - Vegetative Filter S
- Page 63 and 64: Section 3.2.3 - Vegetative Filter S
- Page 65 and 66: Section 3.2.3 - Vegetative Filter S
- Page 67 and 68: Section 3.2.4 - Grassed Channel 3.2
- Page 69 and 70: Section 3.2.4 - Grassed Channel 3.2
- Page 71 and 72: Section 3.2.4 - Grassed Channel 3.2
- Page 73 and 74: Section 3.2.4 - Grassed Channel max
- Page 75 and 76: Section 3.2.5 - Enhanced Swale 3.2.
- Page 77 and 78: Section 3.2.5 - Enhanced Swale Chan
- Page 79 and 80: Section 3.2.5 - Enhanced Swale B. G
- Page 81: Section 3.2.5 - Enhanced Swale High
- Page 85 and 86: Section 3.2.5 - Enhanced Swale 3.2.
- Page 87 and 88: Section 3.2.6 - Infiltration Trench
- Page 89 and 90: Section 3.2.6 - Infiltration Trench
- Page 91 and 92: Section 3.2.6 - Infiltration Trench
- Page 93 and 94: Section 3.2.6 - Infiltration Trench
- Page 95 and 96: Section 3.2.6 - Infiltration Trench
- Page 97 and 98: Section 3.2.6 - Infiltration Trench
- Page 99 and 100: Section 3.2.7 - Soakage Trench 3.2.
- Page 101 and 102: Section 3.2.7 - Soakage Trench •
- Page 103 and 104: Section 3.2.8 - Surface Sand Filter
- Page 105 and 106: Section 3.2.8 - Surface Sand Filter
- Page 107 and 108: Section 3.2.8 - Surface Sand Filter
- Page 109 and 110: Section 3.2.8 - Surface Sand Filter
- Page 111 and 112: Section 3.2.8 - Surface Sand Filter
- Page 113 and 114: Section 3.2.8 - Surface Sand Filter
- Page 115 and 116: Section 3.2.8 - Surface Sand Filter
- Page 117 and 118: Section 3.2.9 - Bioretention Areas
- Page 119 and 120: Section 3.2.9 - Bioretention Areas
- Page 121 and 122: Section 3.2.9 - Bioretention Areas
- Page 123 and 124: Section 3.2.9 - Bioretention Areas
- Page 125 and 126: Section 3.2.9 - Bioretention Areas
- Page 127 and 128: Section 3.2.9 - Bioretention Areas
- Page 129 and 130: Section 3.2.9 - Bioretention Areas
- Page 131 and 132: Section 3.2.9 - Bioretention Areas
Section 3.2.5 - Enhanced Swale<br />
Step 8<br />
Step 9<br />
Design inlets, sediment forebay, and underdrain system.<br />
See <strong>Chapter</strong> 4 and <strong>Chapter</strong> 5 for more details.<br />
Prepare Vegetation and Landscaping Plan.<br />
A landscaping plan for an enhanced swale should be prepared to indicate how the<br />
enhanced swale system will be stabilized and established with vegetation.<br />
3.2.5.7 Design Example<br />
Basic Data<br />
Small commercial lot 300 feet deep x 145 feet wide.<br />
• Drainage area (A) = 1.0 acres<br />
• Rainfall (P) = 1.2 inches (water quality event)<br />
• Run<strong>of</strong>f coefficient (R v ) = 0.70<br />
Water Quality Peak Flow<br />
Compute the Water Quality Protection <strong>Volume</strong> in inches over the drainage area:<br />
WQ<br />
v<br />
=<br />
v<br />
P * R = 1.2*0.70 = 0.84inches<br />
Compute the Water Quality Peak Flow (see the grassed swale example for detailed<br />
calculations).<br />
Q wq<br />
1.0<br />
= 940csm<br />
ac<br />
* * 0.84in<br />
= 1.23 cfs<br />
in<br />
640 ac<br />
2<br />
mi<br />
Pre-treatment <strong>Volume</strong> (Forebay)<br />
Compute the size <strong>of</strong> the sediment forebay (assume 80% <strong>of</strong> site is impervious)<br />
V<br />
pre<br />
= ( 0.80)(0.1")(1' /12") = 1.2*0.70 = 0.0067acre- ft<br />
Enhanced Swale Design<br />
Determine the swale dimensions (assume trapezoidal channel with max depth <strong>of</strong> 18 inches).<br />
The Q wq will be utilized to size the channel. The maximum flow depth <strong>of</strong> 4 inches is allowed for<br />
water quality design. A maximum flow velocity <strong>of</strong> 1.0 foot per second for water quality<br />
treatment is required. For Manning’s n use 0.15 for medium grass, 0.25 for dense grass, and<br />
0.35 for very dense Bermuda-type grass.<br />
Input variables:<br />
n = 0.15<br />
D = 1’<br />
Page 3 - 76<br />
<strong>Volume</strong> 2, Technical Guidance
Change language