Multiple basins
Multiple basins
(OP)
I have a 60 Ac project site with multiple basins, site laid out by architect which I have to abide by. My city requires using unit hydrograph method to size basins and store only incremental runoff. Is it Ok to compute the incremental runoff volume for the whole site and size the basins based on proportions (contributing areas)? It is one development so I believe I can assume the basin characteristics are similar.
Thanks
Thanks





RE: Multiple basins
good luck
RE: Multiple basins
If ponds discharge into each other, you need to compute an outflow hydrograph, route it through the conveying channel, and add it to the drainage basin hydrograph to compute the combined inflow hydrograph for the downstream basin.
RE: Multiple basins
To test whether or not this is a true statement, try it both ways. Given that the precipitation data you are likely to have available has a typical statistical error of plus or minus 30%, it seems very unlikely that you would see any differences in your design either way. In 60 acres how many sub-basins and how much variability in rainfall and runoff can there be ?
Also remember, that you are not likely to be required by the reviewing agency to design for more than a few of the many possible storms. So there will always be some probability, however small, that a storm larger than any considered in your design will occur during the useful life of your pond(s) and conveyance system(s).
You can, by careful selection of design storms and a healthy dose of safety factors, reduce this possibility to a very small number; but you can never, economically reduce it to zero.
good luck
RE: Multiple basins
RE: Multiple basins
RE: Multiple basins