Hydraulics & Waterways

Oral

393961 - Design and Analysis of Channel Restoration Features in Confined Urban Rivers

Wednesday, June 6
4:00 PM - 5:30 PM
Location: Regency Room

Rivers and streams have been severely impacted by anthropogenic development and urbanization. In some urban corridors, such as the Los Angeles (LA) River, streams have been completely channelized and lined with concrete to efficiently convey floods and minimize erosion. These original goals have largely been accomplished, but have resulted in degraded ecosystem services. Flow depths are uniform across the channel and velocities are increased with no refugia for aquatic species. Revitalization can be accomplished by considering channel functions over a range of low to high flows, thereby converting a single purpose (flood conveyance) waterway to a multi-purpose (flood control, habitat, aesthetics, and recreation) feature of the urban landscape.

This study develops and evaluates methods that can be implemented within confined urban channels to improve ecosystem function at low flows without significantly raising flood stage at high flows. Using the LA River as a pilot site, the research focus is to redesign the channel bed by developing concepts for some of the following features: meandering low flow channel, variable width low-flow channel, pool-riffle sequence, flow deflectors (boulder clusters, transverse vanes, notched drop structures), multi-thread flow paths, backwaters, and variable roughness elements (cobbles, vegetation). Design concepts are tested and evaluated with a two-dimensional (2-D) numerical model by applying Habitat Suitability Index (HSI) parameters. Habitat suitability and effect on flood stage are assessed for each of the proposed ecological enhancement methods. Aquatic species habitat is improved by creating areas of slow velocity refugia and adding diversity and complexity to the flow field.

Nathan J. Holste, M.S., P.E., M.ASCE

Hydraulic Engineer
US Department of Interior, Bureau of Reclamation

Nathan J. Holste (M.S., P.E., M.ASCE) is a hydraulic engineer with the Bureau of Reclamation in Denver, Colorado. Nathan has worked in the Sedimentation and River Hydraulics Group in Reclamation's Denver Office for almost 4 years. Previously, he spent 5 years as a hydraulic engineer in Reclamation's Albuquerque Area Office. Nathan continues to work extensively on the Middle Rio Grande in New Mexico, in addition to rivers in California and the Pacific Northwest. He primarily designs habitat restoration and bank protection projects and performs hydraulic and sediment modeling.

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393961 - Design and Analysis of Channel Restoration Features in Confined Urban Rivers



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