The City of Austin owns and maintains at least 63 high hazard dam structures across the City. State and City dam safety criteria require these high hazard dams to be able to safely pass the Probable Maximum Flood (PMF) without failing. Our project team performed preliminary design assessments of the 63 dams to determine whether or not the dams were capable of safely passing the PMF, and if not, to perform preliminary designs of mitigation efforts to allow the dams to safely pass the PMF. We provided the following services:

Assisted in developing the hydrologic models for the 63 dams as part of the preliminary design services

Calculated times of concentration for contributing runoff and developed HEC HMS models.

Delineated drainage boundaries for each of the 63 structures based on available information and site visits

Performed “peer review” of the proposed FNI methodologies for preliminary risk assessment from a theoretical breach and the overall structure ranking

Provided input to the methodologies including technical publications on calculating breach width and breach side slopes, flowchart diagram to depict various evaluation steps, and a “sensitivity analysis” for dam breach velocity related to attenuation length

Prepared memorandums summarizing the results of the peer review

Under final design services, assisted the project team with developing hydrologic and hydraulic models for Pond Dams 26, 220, 267, 337, 581, and 726