Annualmeeting:2017 CSDMS meeting-010

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The competition between frequent and rare flood events: the impact on erosion rates and landscape form.

Jordan Adams, Tulane University New Orleans Louisiana, United States. jadams15@tulane.edu
Nicole Gasparini, Tulane University New Orleans Louisiana, United States. ngaspari@tulane.edu
Gregory Tucker, University of Colorado Boulder Boulder Colorado, United States. gtucker@colorado.edu
Erkan Istanbulluoglu, University of Washington Seattle Washington, United States. erkani@u.washington.edu


[[Image:|300px|right|link=File:]]It has been hypothesized that large, rare flooding events in semi-arid to arid climate regimes may do more erosive work than the frequent storm events that occur in humid or temperate climates. Previous work has demonstrated that added variability in modeled climate or water discharges may be linked to changes in landscape form or channel characteristics. Many landscape evolution models do not capture hydrograph dynamics, so they may miss critical aspects linking flood events and erosion. To explore how different climates shape landscapes, this work uses a hydrodynamic model to simulate flooding and erosion processes. Precipitation time series, based on observed event frequency data from NOAA, are used to differentiate modeled wet and dry regimes. The drier regime is characterized by a heavy-tailed flood probability distribution, where the rarest events have a greater magnitude than storms of a similar recurrence in wetter regions. Hydrographs driven by these precipitation time series are used to erode the topography of a synthetic watershed. Simulations are run with and without an incision threshold. After 10^4 modeled years, landscape characteristics such as relief and channel concavity can be compared. Total eroded depths are evaluated for the different storm frequencies to explore how individual floods and the cumulative work of all floods sculpt landscapes. We propose when an incision threshold is considered, the higher magnitude events in arid regimes will be more effective at shaping watersheds than events of the same frequency in temperate climates. These results inform the discussion of how fluvial erosion may change if anthropogenic climate change leads to the aridification of presently temperate regimes. Additionally, this study will illustrate how hydrograph shape and duration impact modeled landforms, processes not captured in traditional landscape evolution models.