Fundamental stormwater mgmt question.
Fundamental stormwater mgmt question.
(OP)
I am working on a stormwater management plan for a development that covers approximately 700 acres and intends to increase the overall imperviousness by approximately 20%. There is about 1500 ft releif from one site boundary to the other and four existing drainages (creeks) which currently convey stormwater runoff and snowmelt. Without using pumps and excessive infrastructure, it is tough to keep runoff from entering creeks, as obviously this is what it has been doing naturally; so, what alternatives are available to attenuate flows that have already entered a creek to avoid erosion/water quality issues downstream?





RE: Fundamental stormwater mgmt question.
Mike McCann
MMC Engineering
RE: Fundamental stormwater mgmt question.
That said, with our tough environmental permitting laws (I assume you are in the US), you would be ill advised to try and modify the creek to attenuate flows. The 404 permits will be a long time coming if you do. Better to retain and attenuate flows onsite to the maximum extent possible.
If you do want to pursue the stream modifications, grade control structures can slow or stop bed degradation. Off-line detention basins could be used to scalp peaks off your post construction hydrographs. Bank lining can be used to prevent scour and lateral migration of the channel.
RE: Fundamental stormwater mgmt question.
RE: Fundamental stormwater mgmt question.
I'm in the US, so can't comment on Canadian permitting issues - although I believe the environmental laws in Canada are very stringent. If it is a perennial stream, you may have to prove that there are no fish. That goes for minnows and fry. We have an endangered minnow species here which limits construction in many streams. Plus don't forget about other species such as frogs and beavers.