Projects implementing a stream protection plan must calculate the pre- and post-development runoff rate and quantity for the one- and two-year design storms. The requirements for this plan are fairly vague and dependent on the specifics of the project. Including the percent reductions for rate and quantity along with a description of the project design will help buttress the plan with specifics.
Projects using stream protection to achieve the credit must provide a detailed narrative describing how the stormwater management plan protects the receiving waterway from erosion and keeps runoff below critical levels.
If post-development rate and quantity are not equal to or less than pre-development, the option exists for the civil engineer to design stormwater improvements to enable discharge channels from the site to the receiving stream channels to be protected from erosion. The stormwater management narrative must detail the strategies used and how they protect receiving stream channels from excessive erosion. In this plan the civil engineer verifies that post-development stormwater runoff is below critical values for the receiving waterway.
