HR: 16:45h
AN: H34A-04    [Abstracts]
TI: Transient Landscape Evolution: Important Predictions of Sediment-Flux-Dependent River Incision Models
AU: * Gasparini, N M
EM: nicoleg@alum.mit.edu
AF: Yale University, Department of Geology and Geophysics, New Haven, CT 06511 United States
AU: Whipple, K X
EM: kxw@mit.edu
AF: MIT, Department of Earth, Atmospheric and Planetary Sciences, Cambridge, MA 02139 United States
AU: Bras, R L
EM: rlbras@mit.edu
AF: MIT, Department of Civil and Environmental Engineering, Cambridge, MA 02139 United States
AB: Recent experimental and theoretical studies support the notion that bedload in mountain rivers can both enhance incision rates through wear and inhibit incision rates by covering the bed. These effects may play an important role in the non-steady-state adjustment of fluvial channels to tectonic or climatic perturbation. We use the CHILD numerical model with three different bedrock incision models that include the dual role of the sediment flux to explore the transient behavior of fluvial landscapes. All of the models predict that steady- state channel slopes increase in landscapes with higher uplift rates. However, the incision models predict different transient responses to an increase in uplift rate, and the behavior of each incision model depends on both the magnitude of change in uplift rate and the local drainage area. In some cases, the transient channel behavior is indistinguishable from that predicted for transport-limited alluvial rivers. In other cases, knickpoints form in some or all of the drainage network, as predicted from the detachment-limited stream-power model. In all cases, the response in the lower parts of the network is highly dependent on the response in the upper parts of the network, as well as the hillslopes. As the upper parts of the network send more sediment downstream, channel incision rates may rise or fall and slopes in the lower parts of the channel may infact decrease at times during the transient adjustment to an increase in rock uplift rate. In some cases, channel incision in the upper parts of the network ceases during the transient while the hillslopes adjust to the new uplift rate; drainage density may also change as a function of uplift rate. In summary, our results suggest that if the sediment flux strongly controls bedrock incision rates, then (1) the transient fluvial response will take longer than predicted by the stream-power model, (2) changes in channel slope may be much more complex than predicted by the stream-power model, and (3) changes in the fluvial system will be closely tied to sediment delivery from the hillslopes.
DE: 1825 Geomorphology: fluvial (1625)
DE: 1847 Modeling
DE: 1856 River channels (0483, 0744)
DE: 1862 Sediment transport (4558)
DE: 8175 Tectonics and landscape evolution
SC: Hydrology [H]
MN: Fall Meeting 2005