Multiple Drainage Patterns

There are two scenarios that depend on the basin layout and interaction and it is not clear from your question if you have multiple discharge points, one from each basin, or if all three basins combine to a single discharge point.. The most simple scenario is that all three basins are separate, with no connection or flow through from basin to basin. In this case, you would analyze each basin separately. If one basin does not quite meet the requirements for LEED, but another basin can more than meet the requirements and make up for the deficient basin, then you may still be able to meet the LEED requirements as you add the results together. The more complicated analysis is if the basins flow through each other (they are essentially sub-basins) in which case, you may want to analyze the sub-basins and determine if there is the opportunity to reduce the peak flow rate based on timing of the discharge from the separate sub-basins. Of course, the volume will be additive from basin to basin. In any case, it is not appropriate to average the separate calculations, unless you developed a weighted average.. It is more probable that you will analyze each basin and add the reults together to get the combined result.