Lab 9 LAB 9-Stream Flow and Floods Key Ideas Exogenic processes Weathering Mass

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Lab 9 LAB 9-Stream Flow and Floods Key Ideas Exogenic processes Weathering Mass wasting Geomorphic agent Load Surface runoff Overland flow Sheet wash Base flow Gaging station Recurrence interval Discussion Exogenic Geomorphic Processes are the exogenic processes that erode rock matter from higher positions and transport it to be deposited in lower positions. Exogenic processes work to wear down high areas and fill in low areas to reduce overall relief on the earth's surface. Weathering is the chemical or physical breakdown of rocks. When gravity acting alone is the fermed mass wasting. For example, it is mass wasting when a rock falls off a cliff to the surface below Generally, though, erosion, transportation, and deposition require some kind of moving medium, or geomorphie agent, for the weathered particle to move. These geomorphic agents include flowing water blowing wind, waves, and moving ice. Because of the very large number of streams of a variety of sizes on the earth, flowing water does more total overall geomorphic work than any of the other geomorphic agents bigger and many more weathered particles than it can under lower energy conditions. W geomorp hen a geomorphic agent has high energy, like a stream has during a flood, it can carry much hic agent undergoes an energy decrease, like when stream velocity slows, it can no longer carry hen a so much or such large particles and it must deposit some. Solid and chemical materials being moved by a geomorphic agent is its load. Surface Runoff A stream is the channelized flow of water. Most of the water in stream channels arrives at the earth's surface via precipitation, especially rain. When rain hits the earth's surface, some of the water might infiltrate (seep) into the void spaces within the soil and sediments, but if those voids become filled with water, additional rainfall will have to remain at the surface. The accumulating surface water will naturally flow downslope over the land surface as surface runoff, also known as overland flow. At first overland flow consists of a thin blanket of unchannelized sheet wash, but sheet wash soon starts to concentrate into chance depressions, making those shallow depressions larger and deeper by erosion. In this way, the surface runoff is starting to form a small channel for itself. rather than infiltrate into the subsurface result in a large number of stream channels. Surface runoff is favored by the presence of solid surface materials with few pore spaces, such as surface exposures of bedrock instead of loose soil or sediment, or surface materials dominated by the very small clay-sized Characteristics of the land surface that encourage arriving rainwater to flow over the ground clasts. Soil, sediment, and even rock composed predominantly of larger clasts, such as sand, tend to 79 GEO 121 D-G - Spring 20