preview

Quaternary Geological Map

Decent Essays
Open Document

Developing a Quaternary geological map in flood prone areas, typically on alluvial fans was recognized by the National Research Council (NRC, 1996) and by FEMA in there 2003 guidebook. FEMA region IX gave the California Department of Water Resources the responsibility of monitoring and tracking alluvial fan hazards (FEMA, 2003). The California Department of Water Resources has an Alluvial Fan Task Force (AFTF) so that there would more research on alluvial fans and how they contribute to flood hazards (Benrossian, T.L, 2014). They have map 10 counties in southern California in developed areas seen in figure 2. However, there are no detailed maps on Quaternary deposits in unincorporated areas.
The unincorporated area of Salton Sea Beach, Imperial …show more content…

In the upper corer of the topo map, it shows the same feature that was observed in figure 6, figure 7 and figure 8, where the ancient shoreline of the Salton Sea once resided. Southwest of the topo map is shows contours lines evenly space-out and directional flow of small channels which is evident of flash flooding. So, that area is a flood plain or a sheet flow that has eroded the base of the alluvial fan. The alluvial fan is very distinctive in the topo map where the active channel flows downstream through a laterally confined mountainous valley that cuts through the alluvial fan, ancient shoreline and bleeds to a non-confined lowland of the flood …show more content…

Characterizing the morphology of the alluvial fan with the 1-meter DEM will help to further delineate the evolution of the fan. Two profiles of the alluvial fan were analyzed by creating traces along the alluvial fan seen in figure 3b and figure 3c. The elevation of figure 3b and figure 3c was traced with ArcGIS and calculated using MatLab. The cross-sections of the alluvial fan show the curvature of the fan morphology. These traces align in the west - east direction shown in figure 3b that corresponds to the profile of figure 11. Figure 3c alignment is in the north - south direction and corresponds to profile figure 12. Where the traces end, it marks the change of the slope profile of the fan. It is difficult to see but the cross-section from a to g starts out convex to concave retrospectivity. According to Stock J.D. (2008) how sediments are transported; longer profiles are commonly concave up and the shorter fans are generally convex. In contrast, the cross-sections of figure 9 show how the sediments are dispersed. There is higher density of material in profile A and has a slight convex morphology. As you move towards profile G a slight concave morphology can be

Get Access