Hydrologic Alteration and Restoration of Regulated Rivers

Along the Colorado River in Grand Canyon, sediment moves between the active channel, near-channel sandbars, and upland aeolian dunefields. Photo by Joel Sankey, USGS.

River corridors are more than the river itself; the landforms that make up river systems include the active channel, floodplains, terraces, and uplands. Shaped by flowing water, overbank floods, and wind, these landforms represent the exchange, or connectivity, of sediment as it transits within the river system. And sediment connectivity is more than a physical process: the landforms that are created and maintained provide habitat for aquatic invertebrates, native fish, and riparian vegetation communities.

Changes to river flow can have profound impacts on the pathways and magnitude of sediment transfer within river corridors, and that’s especially true downstream of large dams that alter hydrologic regimes. My work uses field surveys (including ground-based lidar and total station topographic mapping) in concert with remote sensing (such as satellite imagery and aerial photogrammetry) to quantify the relationship between hydrologic alteration and sediment transport over hundreds of miles of river corridors.

Much of my research into the effects of altered hydrology on sediment connectivity takes place in dryland rivers of the Southwestern U.S., in particular the Colorado River in Grand Canyon. Over the past several years, I’ve been working with colleagues at the U.S. Geological Survey’s Southwest Biological Science Center to use ground-based lidar, multibeam sonar, and aerial photogrammetry to track the evolution of landforms along the Colorado River and to understand how sediment connectivity is linked back to the flood regime of this highly-managed dryland waterway.

At the same time that I’ve been uncovering the links between hydrology and river corridor eco-geomorphology, I’ve been working with colleagues to develop flow regimes and dam releases that promote water delivery, hydropower generation, and which are also capable of maintaining or restoring physical and biological processes to this iconic landscape.

To learn more about the work we’ve done in Grand Canyon to link hydrology and biophysical processes, see our papers in Environmental Research Letters and Progress in Physical Geography.

Alan Kasprak
Alan Kasprak
Assistant Professor of Geoscience

I study how rivers work, how we affect them, and the ways that we can restore their physical and ecological processes.