Risk Analysis as a Tool to Determine Spillway Design Capacities

by Douglas Toy, ADWR, Phoenix, United States,
Dan Lawrence, ADWR, Phoenix, United States,

Document Type: Proceeding Paper

Part of: Hydraulics/Hydrology of Arid Lands (H²AL)


Lyman Dam is an earth and rockfill structure located on the Little Colorado River approximately 11 miles south and upstream of St. Johns, Arizona. Several studies examining the safety and possible repairs have been completed on the dam. In 1989, a feasibility study indicated that approximately 12.5 million dollars would be needed to reconstruct the dam to safely pass the Probable Maximum Flood (PMF). Lack of funding has heightened awareness of the need to carefully allocate resources. Most recently, ADWR, Apache County Flood Control District and the consulting firm of Dames and Moore completed a risk assessment of the potential for overtopping failure under several repair options. The study did not include a direct assessment of repairs needed to strengthen the downstream slope. This paper is a report of that study.

Subject Headings: Risk management | Spillways | Hydraulic design | Dam failures | Embankment dams | Dam safety | Failure analysis | Feasibility studies | Arizona | United States | Colorado River

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