TWM helped the City develop a stormwater assessment plan to aid in establishing a comprehensive approach for future improvements. Through the use of mobile LiDAR and conventional surveying techniques, TWM developed a working GIS database of the City’s storm sewer system and culvert crossings. HEC-RAS analysis was performed for the numerous creeks throughout the City to ensure existing culverts were sized sufficiently to prevent roadway flooding and overtopping and a PCSWMM model was created to analyze the ponding limits of undersized storm sewers.
Mobile LiDAR was used to collect roadway and ground elevation data. Upon the completion of analysis, TWM developed a decision matrix in conjunction with the City to determine which projects and improvements represented the largest flood reduction for the best value. A brief review of Washington’s stormwater code of ordinances was completed and revisions were provided to ensure future developments are constructed responsibly. TWM is currently working to create bid-ready plans for 10 priority projects established as part of this assessment.