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Interim Hydromodification Criteria
Visit the Standard Urban
Stormwater Management Plan (SUSMP) and Hydromodification
workgroup page to up to date documents.
Regional Water Quality Control Board Order R9-2007-0001
Provision D.1.g (6) (Board Order) requires the County of
San Diego and its NPDES Co-permittees to identify Interim
Hydromodification Criteria (IHC) within 365 days of Order
adoption (i.e., by January 24, 2008). The interim criteria
will apply until the final Hydrograph Modification
Management Plan (HMP) is implemented. The IHC is described
in the order as “an interim range of runoff flow rates
for which Priority Development Project post-project runoff
flow rates and durations shall not exceed pre-project
runoff flow rates and durations.” The purpose of the IHC
is to prevent development-related changes in stormwater
runoff from causing, or further accelerating, stream
channel erosion or other adverse impacts to beneficial
stream uses. This memorandum provides background on
fluvial geomorphology and hydrograph modification
management, describes flow control criteria applied in
other HMPs, and provides a recommendation for developing
the San Diego IHC.
San Diego County Low Impact Development (LID)
Requirements
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