Process and Solution
Clear Creek Solutions used WWHM-SWMM (HSPF hydrology linked to SWMM hydraulics) to model the development and adjacent drainage areas and the city storm drainage pipe system down to the tide gate and Puget Sound.
Tidal influences were included in the SWMM hydraulics.
Clear Creek Solutions ran the WWHM-SWMM model for the period of October 1948 to September of 2009.
A stage frequency analysis was then performed on the annual maximum stage values.
WWHM-SWMM simulated stage data were searched for events that produced stages that were equal or nearly equal to the values in the stage frequency analysis.
Six events were then selected for further analysis.
Peak stages for all six events for both the existing and developed conditions were computed in 12 different model runs using WWHM-SWMM’s TurboSWMM feature.
Using TurboSWMM the long SWMM5 runs that would normally take days to complete were run in only a few hours using multiple computer co-processors.