My research is focused on sediment transport and sedimentology, and the physics linking sediment transport, sediment grain size, and channel morphology in rivers. Much of my work over the past two decades has been on developing new methods for making continuous measurements of suspended-sediment transport and grain size in rivers.
I received my Bachelor's degree from the Massachusetts Institute of Technology in 1988, my Master's degree from the University of Washington in 1991, and my doctorate from the University of Washington in 1997. I have authored or co-authored over 97 peer-reviewed publications in the scientific literature that have received over 2300 citations. I began my career with the USGS in 1993 in the National Research Program of the Water Resources Mission Area and, in 2007, moved my research project to the Southwest Biological Science Center's Grand Canyon Monitoring and Research Center.
Science and Products
Filter Total Items: 18
Importance of measuring discharge and sediment transport in lesser tributaries when closing sediment budgets
Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a river reach is in a state of sediment accumulation, deficit or stasis. Many sediment-b
Long-term continuous acoustical suspended-sediment measurements in rivers – Theory, evaluation, and results from 14 stations on five rivers
We have developed a physically based method for using two acoustic frequencies to measure suspended-silt-and-clay concentration, suspended-sand concentration, and suspended-sand median grain size in river cross sections at 15-minute intervals over decadal timescales. The method is strongly grounded in the extensive scientific literature on the scattering of sound by suspensions of small particles
Water clarity of the Colorado River—Implications for food webs and fish communities
The closure of Glen Canyon Dam in 1963 resulted in drastic changes to water clarity, temperature, and flow of the Colorado River in Glen, Marble, and Grand Canyons. The Colorado River is now much clearer, water temperature is less variable throughout the year, and the river is much colder in the summer months. The flow—regulated by the dam—is now less variable annually, but has larger daily fluctu
Sediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads
The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology; thus, it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change. We analyzed a suite of sediment transport and geomorphi
Using 15-minute acoustic data to analyze suspended-sediment dynamics in the Rio Grande in the Big Bend Region
The Rio Grande in the Big Bend region is subject to rapid geomorphic change consisting of channel narrowing during years of low flow, and channel widening during rare, large, long duration floods. Since the 1940s, there have been large declines in mean and peak stream flow, and the channel has progressively narrowed. Large, channel widening floods are infrequent and have failed to widen the channe
Building sandbars in the Grand Canyon
In 1963, the U.S. Department of the Interior’s Bureau of Reclamation finished building Glen Canyon Dam on the Colorado River in northern Arizona, 25 kilometers upstream from Grand Canyon National Park. The dam impounded 300 kilometers of the Colorado River, creating Lake Powell, the nation’s second largest reservoir.
By 1974, scientists found that the downstream river’s alluvial sandbars were erod
Inaccuracies in sediment budgets arising from estimations of tributary sediment inputs: an example from a monitoring network on the southern Colorado plateau
Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain-size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a channel reach is in a state of sediment accumulation, deficit or stasis. Many studies
Geomorphic change in the Limitrophe reach of the Colorado River in response to the 2014 delta pulse flow, United States and Mexico
A pulse of water was released from Morelos Dam into the dry streambed of the Colorado River in its former delta on March 23, 2014. Although small in relation to delta floods of a century ago, this was the first flow to reach the sea in nearly two decades. The pulse flow was significant in that it resulted from an international agreement, Minute 319, which allowed Colorado River water to be used fo
Sand pulses and sand patches on the Colorado River in Grand Canyon
Alluvial sandbars occur in lateral recirculation zones (eddies) along the Colorado River in Grand Canyon National Park (Schmidt, 1990). Resource managers periodically release controlled floods from the upstream Glen Canyon Dam to rebuild these bars (Grams et al., 2015), which erode during fluctuating dam releases, and by hillslope runoff and wind deflation (Hazel et al., 2010). Because the dam blo
Technical note: False low turbidity readings from optical probes during high suspended-sediment concentrations
Turbidity, a measure of water clarity, is monitored for a variety of purposes including (1) to help determine whether water is safe to drink, (2) to establish background conditions of lakes and rivers and detect pollution caused by construction projects and stormwater discharge, (3) to study sediment transport in rivers and erosion in catchments, (4) to manage siltation of water reservoirs, and (5
Causes of variability in suspended‐sand concentration evaluated using measurements in the Colorado River in Grand Canyon
Rivers commonly exhibit substantial variability in suspended‐sand concentration, even at constant water discharge. Here we derive an approach for evaluating how much of this variability arises from mean bed‐sand grain size. We apply this approach to the Colorado River in Grand Canyon, where discharge‐independent concentration of suspended sand varies by more than a factor of 23 (N = 1.4 × 106). Th
A physically based method of combining ADCP velocity data with point samples to compute suspended-sand discharge -- Application to the Rhone River, France
Measuring suspended-sand flux in rivers is a challenge since sand concentrations are highly variable in time and space throughout a river cross section. Most of the present methodologies rely on point or depth-integrated sampling (Nolan et al., 2005, Topping et al., 2016). The standard method estimates mean concentration and multiply it by discharge to compute the suspended-sand discharge. Here, w
River Sediment Dynamics
Sediment controls the physical habitat of river ecosystems. Changes in the amount and areal distribution of different sediment types cause changes in river-channel form and river habitat. The amount and type of sediment suspended in the water column determines water clarity. Understanding sediment transport and the conditions under which sediment is deposited or eroded from the various...
Surveyed peak-stage elevations, coordinates, and indicator data of strandlines from large floods on the Colorado River in Grand Canyon National Park, Arizona
These data provide a comprehensive survey of peak-stage indicators along the Colorado River corridor between river mile (RM) 0 and RM 87 (see Figure 1 in the associated USGS-SIR). In 2008, the locations of peak-stage indicators in three short reaches downstream from RM 87 were measured using a handheld GPS unit (see Appendix 1 in the associated USGS-SIR). Total-station measurements were made using
Suspended-sediment, bed-sediment, and in-channel topographical data at the Green River at Mineral Bottom near Canyonlands National Park, and Colorado River at Potash, UT stream gages
Sediment Data: These data include (1) physical suspended-sediment sample data including suspended silt and clay concentration, suspended-sand concentration, and suspended-sand grain size distribution, (2) bed-sediment sample data with complete grain size analyses, and (3) 15-minute acoustical sediment data measured using a multifrequency array (1MHz and 2MHz) of sidelooking acoustic Doppler profil
Measurements of bed grain size on the Colorado River in Grand Canyon National Park, Arizona - 2000 to 2014
These data were compiled to better understand sedimentation patterns on the bed of the Colorado River in Grand Canyon National Park, and the way these patterns relate to suspended sediment grain size and concentration. These data were collected by the US Geological Survey Grand Canyon Monitoring and Research Center from 2000 to 2014, primarily using the "Flying Eyeball" underwater imagin
Topographic data, historical peak-stage data, and 2D flow models for the lowermost Little Colorado River, Arizona, USA, 2017
These data were compiled to accompany flow modeling work on Little Colorado river above the mouth (USGS gage 09402300). The data include example models in FaSTMECH and SToRM solvers in the iRIC framework, topographic data collected by LiDAR and total station in June 2017, and high water marks from nine historic floods. Other data also include location and other information for control points and g
Geomorphic Change Data for the Little Colorado River, Arizona, USA
These data include geospatial files (shapefiles and orthorectified raster images) and an input hydrograph (csv) for a 1-dimensional unsteady hydrologic model. Shapefiles consist of active channel boundarys and channel centerlines of six reaches of the LCR beginning ~4.5 km above Grand Falls, AZ, and ending ~12.8 km downstream from Cameron, AZ. These reaches are (1) the ~4.5 km above Grand Falls re
Geomorphic Change-Sediment Transport Data for the Little Colorado River, Arizona, USA
These data were compiled to accompany flow modeling work on Little Colorado river above the mouth (USGS gage 09402300). The data include topographic data collected by LIDAR and total station in June 2017, high water marks from nine historic floods, and control points and gage structures. Topographic data include ground topography collected by LIDAR and channel bathymetry collected by total station
Geomorphic Change-Sediment Transport Data for Kanab Creek, Arizona USA
These data were compiled to accompany flow modeling work on Kanab Creek near the mouth (USGS gage 09403850). The data include topographic data collected by a remote sensing detection light detection and ranging (LIDAR) system and surveying total station in June 2017, high water marks from six floods from 2011 to 2013, and control points and gage structures. Topographic data include ground topograp
Science and Products
- Publications
Filter Total Items: 18
Importance of measuring discharge and sediment transport in lesser tributaries when closing sediment budgets
Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a river reach is in a state of sediment accumulation, deficit or stasis. Many sediment-bLong-term continuous acoustical suspended-sediment measurements in rivers – Theory, evaluation, and results from 14 stations on five rivers
We have developed a physically based method for using two acoustic frequencies to measure suspended-silt-and-clay concentration, suspended-sand concentration, and suspended-sand median grain size in river cross sections at 15-minute intervals over decadal timescales. The method is strongly grounded in the extensive scientific literature on the scattering of sound by suspensions of small particlesWater clarity of the Colorado River—Implications for food webs and fish communities
The closure of Glen Canyon Dam in 1963 resulted in drastic changes to water clarity, temperature, and flow of the Colorado River in Glen, Marble, and Grand Canyons. The Colorado River is now much clearer, water temperature is less variable throughout the year, and the river is much colder in the summer months. The flow—regulated by the dam—is now less variable annually, but has larger daily fluctuSediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads
The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology; thus, it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change. We analyzed a suite of sediment transport and geomorphiUsing 15-minute acoustic data to analyze suspended-sediment dynamics in the Rio Grande in the Big Bend Region
The Rio Grande in the Big Bend region is subject to rapid geomorphic change consisting of channel narrowing during years of low flow, and channel widening during rare, large, long duration floods. Since the 1940s, there have been large declines in mean and peak stream flow, and the channel has progressively narrowed. Large, channel widening floods are infrequent and have failed to widen the channeBuilding sandbars in the Grand Canyon
In 1963, the U.S. Department of the Interior’s Bureau of Reclamation finished building Glen Canyon Dam on the Colorado River in northern Arizona, 25 kilometers upstream from Grand Canyon National Park. The dam impounded 300 kilometers of the Colorado River, creating Lake Powell, the nation’s second largest reservoir. By 1974, scientists found that the downstream river’s alluvial sandbars were erodInaccuracies in sediment budgets arising from estimations of tributary sediment inputs: an example from a monitoring network on the southern Colorado plateau
Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain-size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a channel reach is in a state of sediment accumulation, deficit or stasis. Many studiesGeomorphic change in the Limitrophe reach of the Colorado River in response to the 2014 delta pulse flow, United States and Mexico
A pulse of water was released from Morelos Dam into the dry streambed of the Colorado River in its former delta on March 23, 2014. Although small in relation to delta floods of a century ago, this was the first flow to reach the sea in nearly two decades. The pulse flow was significant in that it resulted from an international agreement, Minute 319, which allowed Colorado River water to be used foSand pulses and sand patches on the Colorado River in Grand Canyon
Alluvial sandbars occur in lateral recirculation zones (eddies) along the Colorado River in Grand Canyon National Park (Schmidt, 1990). Resource managers periodically release controlled floods from the upstream Glen Canyon Dam to rebuild these bars (Grams et al., 2015), which erode during fluctuating dam releases, and by hillslope runoff and wind deflation (Hazel et al., 2010). Because the dam bloTechnical note: False low turbidity readings from optical probes during high suspended-sediment concentrations
Turbidity, a measure of water clarity, is monitored for a variety of purposes including (1) to help determine whether water is safe to drink, (2) to establish background conditions of lakes and rivers and detect pollution caused by construction projects and stormwater discharge, (3) to study sediment transport in rivers and erosion in catchments, (4) to manage siltation of water reservoirs, and (5Causes of variability in suspended‐sand concentration evaluated using measurements in the Colorado River in Grand Canyon
Rivers commonly exhibit substantial variability in suspended‐sand concentration, even at constant water discharge. Here we derive an approach for evaluating how much of this variability arises from mean bed‐sand grain size. We apply this approach to the Colorado River in Grand Canyon, where discharge‐independent concentration of suspended sand varies by more than a factor of 23 (N = 1.4 × 106). ThA physically based method of combining ADCP velocity data with point samples to compute suspended-sand discharge -- Application to the Rhone River, France
Measuring suspended-sand flux in rivers is a challenge since sand concentrations are highly variable in time and space throughout a river cross section. Most of the present methodologies rely on point or depth-integrated sampling (Nolan et al., 2005, Topping et al., 2016). The standard method estimates mean concentration and multiply it by discharge to compute the suspended-sand discharge. Here, w - Science
River Sediment Dynamics
Sediment controls the physical habitat of river ecosystems. Changes in the amount and areal distribution of different sediment types cause changes in river-channel form and river habitat. The amount and type of sediment suspended in the water column determines water clarity. Understanding sediment transport and the conditions under which sediment is deposited or eroded from the various... - Data
Surveyed peak-stage elevations, coordinates, and indicator data of strandlines from large floods on the Colorado River in Grand Canyon National Park, Arizona
These data provide a comprehensive survey of peak-stage indicators along the Colorado River corridor between river mile (RM) 0 and RM 87 (see Figure 1 in the associated USGS-SIR). In 2008, the locations of peak-stage indicators in three short reaches downstream from RM 87 were measured using a handheld GPS unit (see Appendix 1 in the associated USGS-SIR). Total-station measurements were made usingSuspended-sediment, bed-sediment, and in-channel topographical data at the Green River at Mineral Bottom near Canyonlands National Park, and Colorado River at Potash, UT stream gages
Sediment Data: These data include (1) physical suspended-sediment sample data including suspended silt and clay concentration, suspended-sand concentration, and suspended-sand grain size distribution, (2) bed-sediment sample data with complete grain size analyses, and (3) 15-minute acoustical sediment data measured using a multifrequency array (1MHz and 2MHz) of sidelooking acoustic Doppler profilMeasurements of bed grain size on the Colorado River in Grand Canyon National Park, Arizona - 2000 to 2014
These data were compiled to better understand sedimentation patterns on the bed of the Colorado River in Grand Canyon National Park, and the way these patterns relate to suspended sediment grain size and concentration. These data were collected by the US Geological Survey Grand Canyon Monitoring and Research Center from 2000 to 2014, primarily using the "Flying Eyeball" underwater imaginTopographic data, historical peak-stage data, and 2D flow models for the lowermost Little Colorado River, Arizona, USA, 2017
These data were compiled to accompany flow modeling work on Little Colorado river above the mouth (USGS gage 09402300). The data include example models in FaSTMECH and SToRM solvers in the iRIC framework, topographic data collected by LiDAR and total station in June 2017, and high water marks from nine historic floods. Other data also include location and other information for control points and gGeomorphic Change Data for the Little Colorado River, Arizona, USA
These data include geospatial files (shapefiles and orthorectified raster images) and an input hydrograph (csv) for a 1-dimensional unsteady hydrologic model. Shapefiles consist of active channel boundarys and channel centerlines of six reaches of the LCR beginning ~4.5 km above Grand Falls, AZ, and ending ~12.8 km downstream from Cameron, AZ. These reaches are (1) the ~4.5 km above Grand Falls reGeomorphic Change-Sediment Transport Data for the Little Colorado River, Arizona, USA
These data were compiled to accompany flow modeling work on Little Colorado river above the mouth (USGS gage 09402300). The data include topographic data collected by LIDAR and total station in June 2017, high water marks from nine historic floods, and control points and gage structures. Topographic data include ground topography collected by LIDAR and channel bathymetry collected by total stationGeomorphic Change-Sediment Transport Data for Kanab Creek, Arizona USA
These data were compiled to accompany flow modeling work on Kanab Creek near the mouth (USGS gage 09403850). The data include topographic data collected by a remote sensing detection light detection and ranging (LIDAR) system and surveying total station in June 2017, high water marks from six floods from 2011 to 2013, and control points and gage structures. Topographic data include ground topograp