River Geomorphology and Geomorphic Change

Science Center Objects

River channels and their adjacent floodplains are ever evolving in form and composition in response to changing patterns of streamflow, the quantity and size of supplied sediment, and feedbacks with the riparian and aquatic ecosystems. Changes in channel form affect aquatic and riparian habitats, which are important for plants, animals, and insects. Erosion and deposition of river channels and river banks also dramatically affects land used by people, including private property and resources on public lands. Many floodplains and river deposits also include historic and ancient artefacts and cultural sites important to human heritage.

Project Overview

The River Geomorphology and Geomorphic Change project at the U.S. Geological Survey Grand Canyon Monitoring and Research Center includes a range of studies all concerned with describing, quantifying, and predicting geomorphic changes, mostly on large rivers in the western United States. We use a variety of techniques to make high-resolution measurements of river channel bathymetry and topography, including, laser-scanning, photogrammetry, conventional and GPS surveying, and single- and multi-beam echo sounders. We also employ a wide range of analytical tools for topographic modeling, change detection, and classification of river bottom substrate and measurement of sediment grain size.

Geomorphology Projects in Grand Canyon National Park

Erosion of sandbars (beaches) along the Colorado River in Grand Canyon was first reported in the early 1970s, approximately 10 years after completion of Glen Canyon Dam. Since then, scientific studies have been conducted to monitor changes in sandbars and changes in the amount of sand stored on the bed of the river. One of the outcomes of these studies has been the implementation of flow experiments intended to rebuild eroded sandbars, especially by the release of controlled floods, also called “high-flow experiments,” from Lake Powell, the reservoir formed by Glen Canyon Dam. The sediment and geomorphology projects at Grand Canyon Monitoring and Research Center include the collection and processing of data to provide information needed to conduct controlled floods and the research and monitoring needed to evaluate the outcome of each controlled flood and the long-term effects of controlled floods and normal dam operations on sediment-related resources.

Monitoring sandbars in Grand Canyon

Researchers monitoring sandbars in Grand Canyon. (Credit: USGS. Public domain.)

Grand Canyon Sandbar Monitoring:

Topographic surveys are conducted annually at a collection of long-term sandbar monitoring sites to track trends in sandbar size. The data are available through interactive plots of sandbar area and volume spanning 1990 to the most recent survey. For more on Grand Canyon Sandbar Monitoring. Click here to go to the Grand Canyon Sandbar Monitoring project page. Click here to find out more about sandbars in Grand Canyon.   

Sediment Storage in Grand Canyon:

The sandbars exposed along the shoreline of the Colorado River represent only a small fraction of the sand deposits in Grand Canyon, most of which are on the bed of the river in eddies and the channel. Monitoring of sediment storage is conducted to track changes in the supply of sand available to build sandbars. Click here to find out more about sediment storage in Grand Canyon.

River Campsites in Gand Canyon National Park:

Large campsite area in Grand Canyon

Large campsite area in Grand Canyon. (Photo credit: USGS, Public domain.)

Sandbars have been used as campsites by river runners and hikers since the first expeditions to the region more than 100 years ago. Sandbar campsites continue to be an important part of the recreational experience for the more than 25,000 hikers and river runners that visit the Colorado River corridor each year. Click here to learn more about river campsites research in Grand Canyon.  

Surveying and Geodetic Control in the Grand Canyon Region:

Nearly all measurements require spatial referencing to ensure reliability and repeatability. The remote setting and rugged terrain of the Grand Canyon region present significant challenges to accurately positioning geomorphic measurements.

High-flow Experiments:

To manage limited sand resources in Grand Canyon, experimental high flows, which are much higher than base-operations flows, are periodically conducted. High-flow experiments are designed to determine if limited sediment resources can be managed to maintain or increase sandbar size. The Grand Canyon Monitoring and Research Center, part of the Southwest Biological Science Center, conducts monitoring and research studies of these experimental flows. Click here learn more about these experimental flows.

Glen Canyon Dam jet tubes releasing water into the Colorado River for a high flow experiment.

Glen Canyon Dam jet tubes releasing water into the Colorado River for a high flow experiment. The increase in flow of the Colorado River downstream of the dam mobilizes sand at the bottom of the river and that sand rebuilds sandbars in Grand Canyon. (Credit: USGS. Public domain.)