Design Considerations for the North Railroad Alluvial Fan Levee System in Boulder City, Nevada

Wang, Jun; ,

Design Considerations for the North Railroad Alluvial Fan Levee System in Boulder City, Nevada

by Jun Wang, P.E., (M.ASCE),

Document Type: Proceeding Paper

Part of: Watershed Management and Operations Management 2000

Abstract:

This paper presents a drainage study for a flood control levee system in Boulder City, Nevada. This levee system is located below an alluvial fan watershed and was proposed to protect the city from the watershed storm and sediment runoff. Boulder City is located approximately 20 miles east of Las Vegas and 5 miles west of Lake Mead. The west part of the city is situated directly below an alluvial fan and has encountered severe flood damages due to the current inadequate and piece-meal drainage facilities. High concentration of sediment carried by the floods further lessens the integrity of the already undersized earthen channels. As a major component of the city wide master flood control plan, a levee system was proposed to intercept and collect the flood runoff generated within the alluvial fan. A practical procedure was employed by the drainage study in evaluating the unique characteristics of the alluvial fan watershed in terms of hydraulics and sediment transport and develop a conveyance system that would perform under a wide range of hydraulic and sediment transport conditions. Both earthen and fully lined concrete conveyance alternatives were considered by the study. Design parameters of the levee system included the levee wall height, levee cut-off depth, ultimate design slopes, and grade stabilization. The primary objective of the study was to identify extreme watershed conditions the proposed levee system may encounter concerning flood conveyance as well as potentials for erosion and sedimentation and develop an optimal channelconfiguration capable of achieving maximum flood protection and minimized maintenance requirement. The analysis procedure and computational tools that were utilized by the study can be applied in similar alluvial fan flood protection projects that typically involve building a transverse levee structure to collect flood runoffs of multiple and unstable paths. This study was prepared under a contract with the City of Boulder City Public Works Department.

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