Low Impact Development Model
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This example illustrates how the Low Impact Development (LID)
modeling feature works. The data file represents a 29 acre
mixed-use subdivision that has been divided into 9 subcatchments.
Six different types of LID processes have been defined and
deployed within the subcatchments -- rain barrels and an
infiltration trench in subcatchment S1, street planters in
S4, a green roof and permeable pavement area in S5, and
vegetative swales in subcatchments Swale3, Swale4, and Swale6.

After loading the example, select the LID Controls category from
the Data Browser to see what types of LID controls and their design
parameters have been defined for the project. Then use the View |
Query command to locate subcatchments that have been assigned LID
controls or select LID Usage as the Subcatchment Theme to view on
the map. Bring up the Property Editor for a selected subcatchment
and click on the LID Controls property to see how a particular LID
process was deployed within the subcatchment.

Run the example and view a summary of LID performance in the LID
Results section of the Summary Report. Edit one of the LID units
deployed within a subcatchment (e.g., the green roof in subcatchment
S5) to produce a detailed report file for it. Then re-run the
example and open the report file with a text editor (or with Excel)
to view a detailed time history of water fluxes and storage levels
in the LID unit.

To determine the effect that LID usage has on reducing runoff from
this subdivision:
1. From the last run made with LID controls present view the Status
   Report to determine the volume of surface runoff produced (see
   the Runoff Quantity Continuity table in the report). For the 2-yr
   design storm it should be around 0.23 inches.
2. Select the LID Controls category from the Project Browser and
   delete each of the controls except for the Swale.
3. Re-run the project and note the surface runoff value in the
   Status Report. For the 2-yr storm it should be 0.49 inches
   showing that the LID controls provided more than a 50% reduction
   in runoff.
4. To determine the LID impact for the other design storms included
   in the project, re-load the project file and repeat the steps
   above using a different choice of rainfall time series for the
   rain gage. For example, for the 10-yr design storm LID usage
   provides a 37% reduction in surface runoff.