Joel Unema (Former Employee)
Science and Products
Topographic data, historical peak-stage data, and 2D flow models for the lowermost Little Colorado River, Arizona, USA, 2017 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...
Geomorphic Change-Sediment Transport Data for the Little Colorado River, Arizona, USA 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...
Geomorphic Change-Sediment Transport Data for Kanab Creek, Arizona USA 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...
Self-limitation of sand storage in a bedrock-canyon river arising from the interaction of flow and grain size Self-limitation of sand storage in a bedrock-canyon river arising from the interaction of flow and grain size
Bedrock-canyon rivers tend to be supply limited because they are efficient transporters of sediment and not because the upstream supply of sediment is small. A byproduct of this supply limitation is that the finer alluvium stored in these rivers has shorter residence times and smaller volumes than in alluvial rivers. To improve our understanding of disequilibrium sediment transport and...
Authors
David J. Topping, Paul E. Grams, Ronald E. Griffiths, David J. Dean, Scott Wright, Joel A. Unema
Assessing uranium and select trace elements associated with breccia pipe uranium deposits in the Colorado River and main tributaries in Grand Canyon, USA Assessing uranium and select trace elements associated with breccia pipe uranium deposits in the Colorado River and main tributaries in Grand Canyon, USA
Assessing chemical loading from streams in remote, difficult-to-access watersheds is challenging. The Grand Canyon area in northern Arizona, an international tourist destination and sacred place for many Native Americans, is characterized by broad plateaus divided by canyons as much as two-thousand meters deep and hosts some of the highest-grade uranium deposits in the U.S. From 2015...
Authors
Fred D. Tillman, Jessica R. Anderson, Joel A. Unema, Thomas Chapin
Optimal timing of high-flow experiments for sandbar deposition Optimal timing of high-flow experiments for sandbar deposition
Sediment-transport theory and field measurements indicate that the greatest or most efficient deposition of sand in eddies occurs during controlled floods (a.k.a. High-Flow Experiments or HFEs) when the greatest amount of the finest sand is available on the bed of the Colorado River (Topping and others, 2010). Conducting HFEs when the sand on the bed of the Colorado River is depleted and...
Authors
David J. Topping, Paul E. Grams, Ronald E. Griffiths, Joseph E. Hazel, Matthew Kaplinski, David J. Dean, Nicholas Voichick, Joel A. Unema, Thomas A. Sabol
Water-magma interaction and plume processes in the 2008 Okmok eruption, Alaska Water-magma interaction and plume processes in the 2008 Okmok eruption, Alaska
Eruptions of similar explosivity can have divergent effects on the surroundings due to differences in the behavior of the tephra in the eruption column and atmosphere. Okmok volcano, located on Umnak Island in the eastern Aleutian Islands, erupted explosively between 12 July and 19 August 2008. The basaltic andesitic eruption ejected ∼0.24 km3dense rock equivalent (DRE) of tephra...
Authors
Joel A. Unema, Michael H. Ort, Jessica D Larsen, Christina A. Neal, Janet R. Schaefer
Science and Products
Topographic data, historical peak-stage data, and 2D flow models for the lowermost Little Colorado River, Arizona, USA, 2017 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...
Geomorphic Change-Sediment Transport Data for the Little Colorado River, Arizona, USA 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...
Geomorphic Change-Sediment Transport Data for Kanab Creek, Arizona USA 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...
Self-limitation of sand storage in a bedrock-canyon river arising from the interaction of flow and grain size Self-limitation of sand storage in a bedrock-canyon river arising from the interaction of flow and grain size
Bedrock-canyon rivers tend to be supply limited because they are efficient transporters of sediment and not because the upstream supply of sediment is small. A byproduct of this supply limitation is that the finer alluvium stored in these rivers has shorter residence times and smaller volumes than in alluvial rivers. To improve our understanding of disequilibrium sediment transport and...
Authors
David J. Topping, Paul E. Grams, Ronald E. Griffiths, David J. Dean, Scott Wright, Joel A. Unema
Assessing uranium and select trace elements associated with breccia pipe uranium deposits in the Colorado River and main tributaries in Grand Canyon, USA Assessing uranium and select trace elements associated with breccia pipe uranium deposits in the Colorado River and main tributaries in Grand Canyon, USA
Assessing chemical loading from streams in remote, difficult-to-access watersheds is challenging. The Grand Canyon area in northern Arizona, an international tourist destination and sacred place for many Native Americans, is characterized by broad plateaus divided by canyons as much as two-thousand meters deep and hosts some of the highest-grade uranium deposits in the U.S. From 2015...
Authors
Fred D. Tillman, Jessica R. Anderson, Joel A. Unema, Thomas Chapin
Optimal timing of high-flow experiments for sandbar deposition Optimal timing of high-flow experiments for sandbar deposition
Sediment-transport theory and field measurements indicate that the greatest or most efficient deposition of sand in eddies occurs during controlled floods (a.k.a. High-Flow Experiments or HFEs) when the greatest amount of the finest sand is available on the bed of the Colorado River (Topping and others, 2010). Conducting HFEs when the sand on the bed of the Colorado River is depleted and...
Authors
David J. Topping, Paul E. Grams, Ronald E. Griffiths, Joseph E. Hazel, Matthew Kaplinski, David J. Dean, Nicholas Voichick, Joel A. Unema, Thomas A. Sabol
Water-magma interaction and plume processes in the 2008 Okmok eruption, Alaska Water-magma interaction and plume processes in the 2008 Okmok eruption, Alaska
Eruptions of similar explosivity can have divergent effects on the surroundings due to differences in the behavior of the tephra in the eruption column and atmosphere. Okmok volcano, located on Umnak Island in the eastern Aleutian Islands, erupted explosively between 12 July and 19 August 2008. The basaltic andesitic eruption ejected ∼0.24 km3dense rock equivalent (DRE) of tephra...
Authors
Joel A. Unema, Michael H. Ort, Jessica D Larsen, Christina A. Neal, Janet R. Schaefer