Blending Risk Based Analysis with traditional dam hazard analysis for urban dams
Dam Breach Analysis has for many years focused on determining the Hazard Classification which is not conducive to the actual risk of the dam. Henrico County has multiple highly urbanized dams which have a high hazard classification. The county wanted a risk-informed decision analysis performed since the economic impacts to the County as a result of dam failure would be catastrophic. The Cox Road Dam was selected for a planning level pilot study to identify likely dam deficiencies and will identify potential dam rehabilitation measures to lower the dam's risks of failure to a level acceptable to the County. The Cox Road Dam is the middle dam of 3 high hazard dams. While the study focuses on the Cox Road Dam, the other two dams were incorporated into the analysis. As a planning study, the use of traditional hydrologic and hydraulic modeling methods were used along with the addition of the draft FEMA Project Prioritization Tool to estimate the likelihood of failure for static, hydrologic, and seismic failure modes. The use of traditional dam hydrologic and hydraulic modeling methods (a HEC-HMS model for hydrology & HEC-RAS 2D hydraulic model) were needed as they are still accepted by VADCR and used for the risk analysis. For this evaluation, we analyzed all three dams in series because the failure of one dam may have a cascading effect resulting in the failure of downstream dams and identify risk reduction measures.
Author Bio
Marie Hauser is a water resources engineer at AtkinsRéalis with 17 years of experience in engineering on a broad range of projects for both public and private clients. She specializes in dam safety, hydrologic and hydraulic analysis consisting of roadway drainage, stream restoration, floodplain management, and stormwater management facilities. Mr. Linville Has worked for Henrico County for 15 years. He first was hired as a design engineer in the Design Division of Henrico County Public Works where he worked on varies road and drainage improvement projects while also maintaining the County’s road inventory. He Is now currently working as a Capital Projects Coordinator in the same division but now in the Floodplain and Dam Safety Section. He is currently responsible for maintaining and monitoring the counties five state regulated dams and assisting with FEMA and County floodplain related inquiries when needed.
