Urbanization and its effects on channel morphology
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A focus on river and stream morphology with a specific emphasis on how urbanization and human impacts affect river channels. In the study of rivers, specifically looking at how the channel geometry changes with time, there are five main physical factors described that affect the channel morphology: (1) bank and bar stability; (2) sediment size distribution; (3) sediment supply; (4) flow variability; and (5) downstream slope, width and height. Understanding how these five factors affect channel form is vital in constructing realistic and accurate models of rivers and how they change over time. It is also important to understand some of the limitations of the combined modeling of all these factors together for a general stream. Research studies are presented in order to further understand what knowledge has been acquired, and what areas are lacking in adequate understanding. Examples of cases where urbanization and land use change have a large impact and almost no impact are examined. It is important to understand what the limiting factors are in such cases, and whether it is possible to mitigate the effects or urbanization by any means other than natural channel phenomenon. A two-dimensional hydrodynamic and sediment transport model is thoroughly described. The model is evaluated and verified, and potential problems and limitations are then discussed. Then a one-dimensional sediment transport and bed variation model is examined and tested using parameter controlled cases. Urbanization increase near rivers and streams reduces the time frame over which certain natural events would have occurred in those channels. The affects of urbanization include but are not limited to changes in streamflow, sediment transport and deposition, channel bank stability, and increased channel widening. The magnitude of these affects will increase over time if careful steps are not taken to minimize the human influence within channels.