25 October 2004
Use alternative roadway layouts that minimize imperviousness.
Reduce road widths.
Limit sidewalks to one side of roads.
Reduce on-street parking.
Use permeable paving materials.
b) Minimize directly connected impervious areas.
Disconnect roof drains. Direct flows to vegetated areas.
Direct flows from paved areas to stabilized vegetated areas.
Break up flow directions from large paved surfaces.
Encourage sheet flow through vegetated areas.
Locate impervious areas so that they drain to permeable areas.
c) Modify drainage flow paths to increase time of concentration (Tc).
Maximize overland sheet flow.
Lengthen flow paths and increase the number of flow paths.
Maximize use of open swale systems.
Increase (or augment) the amount of vegetation on the site.
d) Define the development envelope.
Use site fingerprinting. Restrict ground disturbance to the smallest
Reduce compaction of highly permeable soils.
Minimize size of construction easements and material stockpiles.
Place stockpiles within development envelope during construction.
Avoid removal of existing trees.
Disconnect as much impervious area as possible.
Maintain existing topography and associated drainage divides to
encourage dispersed flow paths.
Locate new development in areas that have lower hydrologic
function, such as barren clayey soils.
5. Evaluate site planning benefits and compare with baseline values. The
modeling analysis is used to evaluate the cumulative hydrologic benefit of
the site planning process in terms of the four evaluation measures.
6. Evaluate the need for Integrated Management Practices (IMPs). If site
planning is not sufficient to meet the site's LID objectives, additional
hydrologic control needs may be addressed through the use of IMPs
(described in Chapter 8). After IMPs are selected for the site, a second-
level hydrologic evaluation can be conducted that combines the IMPs with
the controls provided by the planning techniques. Results of this
hydrologic evaluation are compared with the baseline conditions to verify