Flood Control Improvements on Alluvial Fans

by James D. Schall, Church Engineering, Inc, Newport Beach, United States,
Douglas W. Bender, Church Engineering, Inc, Newport Beach, United States,
Frank J. Peairs, Church Engineering, Inc, Newport Beach, United States,

Document Type: Proceeding Paper

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


Floodplain management on alluvial fans has become an increasingly important issue with continued growth and urbanization in the southwest. The design of flood control facilities for new development on alluvial fans must take into account potential debris flow conditions. A debris flow event results when sediments loading from an undeveloped watershed is very large, for example, after a major fire. Under conditions the volume of sediment can nearly equal the volume of water, creating at times a slurry type flow event that can cause tremendous damage, and possible loss of life. Damage occur during debris flow events not only from floodwaters, but also from impacts such as deposition of sediment in streets and buildings, high impact boulder transport and deposition, unpredictable flow paths and flood-surge inundation. Alternatives for managing urban development on alluvial fans include; mapping and zoning; debris basins; debris transporting channels; and various combinations of these approaches. Selection of the appropriate management approach depends on site specific conditions and generally, no single approach is universally applicable or appropriate. In the case of the Wild Rose residential development, located on an alluvial fan near Corona, California, the best alternative was design of a debris transporting channel. The Wild Rose project is a good case study of the important factors involved in the design of flood control facilities on alluvial fans.

Subject Headings: Hydraulic design | Case studies | Floods | Alluvial channels | Building design | Solids flow | Flow control | Channel flow | California | United States

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