Sandy Drainage Improvement Company Xpswmm Modeling (OR)
WEST Consultants, Inc. (WEST) developed a an XPSWMM model of the existing system of pumps, ditches and pipes that provides interior drainage of the 1,550 acre area managed by the Sandy Drainage Improvement Company (SDIC). The total contributing basin area is approximately 2,560 acres. Multiple communities including Multnomah County and the Cities of Gresham, Fairview, Wood Village, and Troutdale have property located within the project basin. The project area is protected from flooding along the Columbia and Sandy Rivers by as system of levees.

The existing interior drainage system was evaluated for the purpose of updating the FEMA Flood Insurance Rate Maps to reflect localized flooding associated with the interior drainage system. WEST developed a Letter of Map Revision (LOMR) to show the extent and depth of interior flooding.

In addition to the existing conditions modeling, SDIC and the Port of Portland are interested in understanding impacts resulting from planned future development. WEST is developing future conditions models to account for increased impervious areas and reduction flood storage resulting from fill within the floodplain. The future conditions model will evaluate potential upgrades such as creation of additional flood storage, replacement of culverts, channel improvements, and pump station upgrades.