City of Castle Rock Levee Certification (WA)
Levee certification must conform to the Code of Federal Regulations Chapter 44, Section 65.10, which establishes the requirements that must be met prior to levee certification and accreditation by FEMA. WEST Consultants, Inc. (WEST) completed the interior drainage analysis as a requirement for the certification of the levee system operated by City of Castle Rock located in Cowlitz County, Washington.

WEST conducted a field reconnaissance and review of previous analyses, calculations, and studies. A detailed survey of the areas of probable interior flooding was completed by WEST. An HEC-HMS hydrologic model was developed to provide hydrographs for the interior drainage analysis. An unsteady HEC-RAS hydraulic model was created to evaluate the potential for interior flooding. The hydraulic model included pump stations, storage areas, and other unique hydraulic features. The extent of interior flooding was defined by hydraulic analysis and then mapped using Arc-GIS. Other tasks included computation of levee freeboard and evaluation of the erosion potential levee embankment protection.