Incorporating a mechanistic bank failure algorithm into the cellular automaton evolutionary slope and river (Caesar) model, and applying it to a highly erosive reach of the Colorado River, Austin, Texas
Humberson, Delbert G.
Streams are a dynamic part of the Earth's landscape. The altered hydrologic and sedimentologic regimes caused by urbanization bring about changes in channel morphology that are problematic for urban stream management. The amount of time an urban stream needs to stabilize within the new hydrologic and sedimentologic regimes depends upon local variables, but some streams remain unstable 50 years after urbanization has started. In some cases, stabilization may not be possible. The Cellular Automaton Evolutionary Slope and River (CAESAR) model, which is a cellularautomata (CA) landscape evolution model, can help stream managers understand channel evolution over long time periods. Landscape evolution models typically come in two forms, CA based models or vector based models. CA landscape evolution models are capable of routing sediment in single and multi-threaded channels, creating channel scour and deposition, but traditionally have not been able to simulate the lateral migration of a stream. Vector based landscape evolution models, on the other hand, have traditionally been able to simulate lateral channel migration but not multi-threaded flow. Recent progress enables CAESAR to qualitatively simulate lateral channel migration with a deterministic algorithm. This study attempts to improve CAESAR's algorithm for simulating bank failure by using a mechanistic algorithm that incorporates bank slope and bank materials. The new algorithm was applied to a highly erosive reach of the Colorado River in Austin, Texas in order to assess its effectiveness. Results indicate a success, in that regional bank migration occurred as a result of cell by cell bank failure. Furthermore, the failure that occurred was qualitatively realistic. Despite the success, there is room for improvement, and future research should focus on simulating the study site with more detailed input or on incorporating more sophisticated mechanistic bank failure algorithms.
Stream channelization, Stream ecology, Urbanization
Humberson, D. G. (2009). <i>Incorporating a mechanistic bank failure algorithm into the cellular automaton evolutionary slope and river (Caesar) model, and applying it to a highly erosive reach of the Colorado River, Austin, Texas</i> (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.