Geographical Characteristics of the Streams in Urban Areas and Forested Areas
Introduction
We made a field trip to three streams based on the Mill Creek flow system in South part of the Seattle. The aim of the field trip was to study various geographical characteristics of the streams in urban areas and forested areas. We hypothesized that, there are fewer rocks in the urban stream as compared to the forest stream because the urban stream may not have as many sources of sediment while the forest areas have more sources. Also, the urban stream may have smaller rocks or at least rocks of similar sizes (not diverse) while the forest may have a larger breadth of rock sizes. In forested areas, rocks and sediments are held together by the roots of trees and other vegetation over years, from where they harden, making large pebbles. These large pebbles are then eroded to the nearest streams, which accounts for streams near forested areas having larger pebbles (Allan, 2006). On the other hand, urban areas may not have many sources of sediments or the vegetation to hold up the sediments, hence, when erosion occurs, it is the little sediments and soil that is carried to the nearby streams (Allan, 2006). We also hypothesized that the pool areas of streams have larger rocks as compared to the riffle areas.
Large rocks get stuck in the pool areas and then slowly wither away into smaller rocks, but because of the slow velocity in the pool area, there will be more sediments settling in the area (Inwood, 2007). Due to the deep depths and slow currents, more large pebbles are expected to settle at the bottom of the pool area.The sediment composition of streambeds and banks is an important aspect of stream character that influences erosion form, sediment supply, channel forms and hydraulics, and other parameters. The reference site for each parameter includes a basic characterization of the streambed and bank material (Aristide, 2006). For this reason, the study of sediments in the streams is crucial in determining other important aspects such as microhabitats and agricultural activities. However, greater details than what we use in the field trip are required for the study of fish habitats, stream hydraulics, and the riparian ecosystem. HypothesisThere are fewer rocks in the urban stream as compared to the forest stream because the urban stream may not have as many sources of sediment, while the forest areas have more sources.
Also, the urban stream may have smaller rocks or at least rocks of similar sizes (not diverse) while the forest may have a larger breadth of rock sizes.The pool areas of streams have larger rocks as compared to the riffle areas.Materials and methodWe used the gravelometer quadrant to classify pebble sizes into classes. The gravelometer quadrant helped us in measuring, grouping, and counting the pebbles we sampled from various areas of the streams that we visited. First, we selected a reach on near the …
