9 Va. Admin. Code § 25-870-72 - [Repealed effective 7/1/2024] Design storms and hydrologic methods
A.
Unless otherwise specified, the prescribed design storms are the one-year,
two-year, and 10-year 24-hour storms using the site-specific rainfall
precipitation frequency data recommended by the U.S. National Oceanic and
Atmospheric Administration (NOAA) Atlas 14. Partial duration time series shall
be used for the precipitation data.
B. Unless otherwise specified, all hydrologic
analyses shall be based on the existing watershed characteristics and how the
ultimate development condition of the subject project will be
addressed.
C. The U.S. Department
of Agriculture's Natural Resources Conservation Service (NRCS) synthetic
24-hour rainfall distribution and models, including, but not limited to TR-55
and TR-20; hydrologic and hydraulic methods developed by the U.S. Army Corps of
Engineers; or other standard hydrologic and hydraulic methods, shall be used to
conduct the analyses described in this part.
D. For drainage areas of 200 acres or less,
the VSMP authority may allow for the use of the Rational Method for evaluating
peak discharges.
E. For drainage
areas of 200 acres or less, the VSMP authority may allow for the use of the
Modified Rational Method for evaluating volumetric flows to stormwater
conveyances.
Notes
Statutory Authority: § 62.1-44.15:28 of the Code of Virginia; Chapters 68 and 758 of the 2016 Acts of Assembly.
State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.
No prior version found.