Exploring methods to predict, manage, and control alluvial material transport
Project ID: 7796
Principal Investigator: Carrie Scott
Research Topic: Repair and Maintenance
Funded Fiscal Years: 2014
Keywords: alluvial, alluvial fan, alluvial material, colorado river, debris, debris fan, debris basin, ephemeral, ephemeral stream, hydrology, hydrologic, wash, wash fan, sediment, sediment transport
What methods are being implemented by Reclamation, its stakeholders, and other parties to predict, capture, and or control alluvial material that is transported during hydrologic events? What challenges are common and unique among parties and are there ways to share knowledge and collaborate? Which methods have proven to be successful and which have not? Did the parties identify any gaps or limitations in science, computer modeling software, or in laboratory studies? What were the lessons learned?
Need and Benefit
Rainfall events between 2003 and 2005 caused flooding within the Gould and Mule Washes, which are ephemeral streams within the Cibola and Palo Verde Divisions of the Lower Colorado River (River). Flows exiting the termini of these streams washed out sections of Reclamations operation and maintenance roadways, protective river bank structures, and deposited thousands of cubic yards of alluvial material and debris into the River channel. Reclamation Yuma Area Office personnel conducted emergency measures to repair said infrastructure and remove alluvial material from the River channel.
In October 2011, Reclamation personnel conducted a Review of Operation and Maintenance of the Lower Colorado River from the Southerly International Boundary to Davis Dam and observed 10 large alluvial fans within the River channel that were deposited by ephemeral tributary flows. The alluvial fans are constricting channel capacities and have the potential to adversely impact water operations. Increased local river velocities around alluvial fans have the capability to erode and undercut bank structures, which protect adjacent private, public, and tribal lands and facilities. Alluvial fans are potential navigational hazards to the general public, who use the river system for recreational purposes. The Colorado River Indian Tribes (CRIT) have also experienced issues with alluvial fans and have contacted Reclamation's Yuma Area Office for assistance. An example is the "Paradise Point Wash Fan" which has reduced the local channel capacity and impeded access to one of their boat ramps.
Ephemeral stream flooding and alluvial material transport are not unique to the Colorado River Basin nor are they solely a Reclamation problem. The Southern California floods of February 1969 resulted in more than $213 million in property damages and more than 100 lost lives . Ephemeral stream flows have the potential to transport large volumes of material and debris. As an example, runoff from heavy rains in the Huachucan Mountains deposited debris and boulders several feet in diameter south of Sierra Vista, Arizona in 1988 .
For decades the Los Angeles County Department of Public Works, the U.S. Army Corps of Engineers, and other interested parties have utilized debris basins to capture and control material upstream of essential flood-control infrastructure and urbanized areas.
In the past, Reclamation has deployed heavy equipment within river channel boundaries to remove large alluvial fans. With constrained budgets, fish and wildlife considerations, permitting requirements, and a limited timeframe for removal (November through January, when flow in the river is typically low), it has become a heightened challenge to address and remove alluvial fans in an effective manner. Reclamation is looking towards alternative methods to better manage alluvial material prior to its introduction into the river channel.
This scoping effort will provide a means to explore existing methods used by Reclamation, the industry, and other agencies to measure, capture, and or control alluvial material. Controlling alluvial material prior to its introduction into the Lower Colorado has the potential to minimize river channel constrictions, thus maintaining more efficient channel capacities for water delivery. Reducing alluvial material deposits within the river channel will lessen the need to deploy heavy equipment into river channel boundaries to conduct removal operations, will minimize impacts to aquatic species and riparian vegetation, may broaden the time window for conducting maintenance activities, and may reduce maintenance costs.
For a list of sources, refer to the 'Additional Information' section.
Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
Exploring Methods to Predict, Manage, and Control Alluvial Material Transport (final, PDF,
By Carrie Scott
Report completed on September 26, 2014