Tables: Low Impact Development Techniques
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1. Table 1
BMP 2004, Ch 2, p. 18
| Area (sf) |
Land Use |
HSG |
| 17214 |
Lawn (good condition) |
B |
| 10256 |
Lawn (good condition) |
C |
| 3436 |
Impervious (directly connected) |
B |
| 1764 |
Impervious (directly connected) |
C |
Source context and notes
$\mathrm{P}_2 = 3.3$ inches, $\mathrm{P}_{10} = 5.2$ inches, and $\mathrm{P}_{100} = 7.5$ inch
Vegetated Area, $\mathrm{Tc} = 0.32$ hours
125 If sheet flow, $1.6\%$ slope, $\mathrm{n} = 0.24$
135 If shallow conc flow, $1.4\%$ slope, unpaved
| Area (sf) | Land Use | HSG |
| --- | --- | --- |
| 17214 | Lawn (good condition) | B |
| 10256 | Lawn (good condition) | C |
| 3436 | Impervious (directly connected) | B |
| 1764 | Impervious (directly connected) | C |
2. Table 2
BMP 2004, Ch 2, p. 19
| Area (sf) |
Land Use |
HSG |
| 17524 |
Woods (good condition) |
B |
| 1564 |
Lawn (good condition) |
B |
| 1876 |
Lawn (good condition) |
C |
Source context and notes
Nonstructural stormwater management strategies used: minimized land disturbance; minimized compaction; maximized the protection of vegetation; minimized the decrease in post-development time of concentration through retaining existing wooded area; and minimized and disconnected impervious cover.
Vegetated Area, $\mathrm{Tc} = 0.52$ hours
125 lf sheet flow, $1.3\%$ slope, $\mathrm{n} = 0.40$
135 lf shallow conc flow, $2.1\%$ slope, unpaved
| Area (sf) | Land Use | HSG |
| --- | --- | --- |
| 17524 | Woods (good condition) | B |
| 1564 | Lawn (good condition) | B |
| 1876 | Lawn (good condition) | C |
Unconnected Impervious Area, $\mathrm{Tc} = 0.23$ hours
100 lf sheet flow, $2.1\%$ slope, $\mathrm{n} = 0.24$
Note: The time of concentration was developed from the receiving pervious area alone.
3. Table 3
BMP 2004, Ch 2, p. 19
| Distribution of Pervious Areas Receiving Unconnected Impervious Area Runoff |
|
|
| Area (sf) |
Land Use |
HSG |
| 1562 |
Lawn (good condition) |
B |
| 7344 |
Lawn (good condition) |
C |
Source context and notes
| 1876 | Lawn (good condition) | C |
Unconnected Impervious Area, $\mathrm{Tc} = 0.23$ hours
100 lf sheet flow, $2.1\%$ slope, $\mathrm{n} = 0.24$
Note: The time of concentration was developed from the receiving pervious area alone.
| Distribution of Pervious Areas Receiving Unconnected Impervious Area Runoff | | |
| --- | --- | --- |
| Area (sf) | Land Use | HSG |
| 1562 | Lawn (good condition) | B |
| 7344 | Lawn (good condition) | C |
4. Table 4
BMP 2004, Ch 2, p. 20
|
Existing Conditions |
Proposed Conditions (Standard Development) |
Proposed Conditions (Nonstructural Stormwater Management Strategies) |
|
|
|
|
Two-Step Method |
NRCS Method |
| 2-year |
0.15 cfs |
0.48 cfs |
0.29 cfs |
0.27 cfs |
|
0.030 ac-ft |
0.067 ac-ft |
0.043 ac-ft |
0.041 ac-ft |
| 10-year |
0.62 cfs |
1.18 cfs |
.81 cfs |
.78 cfs |
|
0.093 ac-ft |
0.150 ac-ft |
0.116 ac-ft |
0.109 ac-ft |
| 100-year |
1.35 cfs |
2.19 cfs |
1.61 cfs |
1.58 cfs |
|
0.192 ac-ft |
0.261 ac-ft |
0.214 ac-ft |
0.211 ac-ft |
Source context and notes
# Low Impact Development Techniques
Source revision: February 2004.
# Peak Flow Rates and Volumes
| | Existing Conditions | Proposed Conditions (Standard Development) | Proposed Conditions (Nonstructural Stormwater Management Strategies) | |
| --- | --- | --- | --- | --- |
| | | | Two-Step Method | NRCS Method |
| 2-year | 0.15 cfs | 0.48 cfs | 0.29 cfs | 0.27 cfs |
| | 0.030 ac-ft | 0.067 ac-ft | 0.043 ac-ft | 0.041 ac-ft |
| 10-year | 0.62 cfs | 1.18 cfs | .81 cfs | .78 cfs |
| | 0.093 ac-ft | 0.150 ac-ft | 0.116 ac-ft | 0.109 ac-ft |
| 100-year | 1.35 cfs | 2.19 cfs | 1.61 cfs | 1.58 cfs |
| | 0.192 ac-ft | 0.261 ac-ft | 0.214 ac-ft | 0.211 ac-ft |
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