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3. Evaluate site constraints such as available space, soil infiltration
characteristics, water table, slope, drainage patterns, sunlight and shade,
wind, critical habitat, circulation and underground utilities.
4. Identify protected areas, setbacks, easements, topographic features,
subdrainage divides, and other site features that should be protected such
as floodplains, steep slopes, and wetlands.
5. Delineate the watershed and microwatershed areas. Take into account
previously modified drainage patterns, roads, and stormwater conveyance
6. Locate baseline hydrologic and water quality data. In order of preference,
try to locate:
Local stream gage data and site water quality sampling data
Data from a similar area within region
7. Identify applicable local regulations or codes.
Step 3: Develop LID control strategies
Use hydrology as a design element. In order to minimize the runoff potential
of the development, the hydrologic evaluation should be an ongoing part of the design
process. An understanding of site drainage can suggest locations both for green areas
and potential building sites. An open drainage system can help integrate the site with
its natural features, creating a more aesthetically pleasing landscape.
1. Determine the design storm(s). Regulatory requirements for design storms
may also be stipulated in local ordinances, and these may limit or
constrain the use of LID techniques or necessitate that structural controls
be employed in conjunction with LID techniques.
2. Define modeling technique(s) to be employed. Section 5-5.1 includes a
detailed description several available hydrologic models. The model
selected will depend on the type of watershed, complexity of the site
planning goals, familiarity with the model, and level of detail desired.
3. Evaluate current conditions. Use the results of modeling to estimate
baseline values for the four evaluation measures: runoff volume, peak
runoff rate, flow frequency and duration, and water quality.
4. Implement non-structural site planning techniques:
a) Minimize total site impervious area.