Channel Networks
Channels are the arteries of terrestrial and submarine landscapes. They are responsible for transporting the
water and sediment that either build or erode topography. They also transport important environmental nutrients
and act as home to many organisms. Our group is interested in how these networks (both tributary and
distributary) form and organize themselves. To study these questions we utilize field work, analysis of digital
elevation models (DEMs), laboratory experiments, and computer modeling.
Projects:
Growth laws for channel networks incised by groundwater flow: with Dan Rothman (M.I.T.) and David Mohrig (U. Texas Austin)
Wherever infiltration exceeds rainfall, runoff must travel at least partially underground. The reemergence of
groundwater at the surface can then shape topography by a process called seepage erosion. Along with overland
flow, seepage erosion contributes to the initiation and growth of channel networks. Because seepage processes
undermine overlying material, they have been suggested as an explanation of enigmatic amphitheater-headed channel
networks on Earth and Mars. Nevertheless, the role of seepage in producing such channels remains controversial.
Progress requires relating mechanisms of growth to geologic form. By combining field observations from a
kilometer-scale channel network in the Florida Panhandle with physical theory, we are working on unraveling the
processes responsible for seepage network growth.
Read More.
Scaling laws of terrestrial and submarine channel networks: with Dan Rothman (M.I.T.), Doug Jerolmack (U. Penn),
and David Mohrig (U. Texas Austin)
Channels are the most common and dynamically significant morphologic feature of sedimentary systems on the
continental slope, yet the processes by which these channels evolve and organize themselves are incompletely
known. Recent bathymetric surveys have revealed channel networks that are qualitatively similar to their
terrestrial cousins. We are studying submarine channel network scaling relationships between contributing basin
area and the length of channels and their slopes. These scaling relationships have been used by the terrestrial
geomorphology community to analyze drainage basin evolution. We are comparing scaling relationships in submarine
basins with terrestrial basins and several numerical models of basin evolution. We are finding that scaling
relationships are similar in both terrestrial and submarine environments, supporting theoretical arguments that
channel network structure results from the aggretation of random walks.
Read More.
Sediment transport and avuslion triggers on the Niobrara River, NE: with Doug Jerolmack (U. Penn)
and David Mohrig (U. Texas Austin)
The lower section of the sandy braided Niobrara River, Nebraska, has experienced up to 2.5 m of aggradation over
50 years driven by base-level rise due to reservoir construction on the Missouri River. Over two field seasons I have
particiapated in field campaigns aimed at studying the effect of this base-level rise on sediment transport and channel
dynamics. An apparent response has been frequent avulsions due to superelevation of the channel, which has led to the
creation in some reaches of multiple channels separated by vegetated islands. Results suggest that the river is
dynamically adjusted so that the planform geometry has little effect on the routing of flow and sediment through the
river.