ABOUT THIS EARTHCACHE
This EarthCache will bring you to a nice view of the downstream portion of Crooked Creek. There are two parking areas and trailheads (see waypoints). At the posted coords you will be able to see the current and past affects of bank erosion.
LOGGING REQUIREMENTS
In order to log this EarthCache, send me your answers to the following questions either through email or messaging from my profile page.
1a: Look across the river and estimate the height of the bank nearest the river.
1b: Look beyond the nearest bank and estimate the height of the older bank.
2a: Give an example of fluvial erosion and what part of the banks you can see this.
2b: Give an example of mass failure and what part of the banks you can see this.
3: Do you think the dam has made a significant difference in bank erosion here? Please explain your reasoning.
4: Post a pic of you or a personal item with the creek in the background.
If you enjoyed this EarthCache, please consider giving it a favorite point.
WHY HERE?
The dam upstream was completed in 1940 as a from of flood control. From the posted coordinates, you will be able to compare the current bank erosion as well as see historic affects of bank erosion.
BANK EROSION
Bank erosion is the process by which soil and rock materials are removed from the banks of rivers due to the forces exerted by flowing water exceeding the bank's resistance, which is provided by soil cohesion and vegetation.
The energy of the river flow is the primary driver of erosion, and this energy varies across different river systems, along the length of a river, and seasonally. High-energy events, such as floods, significantly contribute to erosion by increasing the river's capacity to transport sediment and by destabilizing riverbanks. The rate at which eroded materials are transported downstream as part of the river's sediment load influences the exposure of riverbanks to further erosion, creating a dynamic and often discontinuous process.
MECHANISMS
There are two primary mechanisms of stream bank erosion: fluvial erosion and mass failure. Fluvial erosion is the direct removal of soil particles by flowing water. The rate of fluvial erosion is determined both by the force of the flowing water and the resistance of the bank material to erosion. Mass failure occurs when the weight of a stream bank is greater than the strength of the soil, causing the bank to collapse. This process is dependent upon a number of factors including the internal strength of the soil, soil-water content, and vegetation. These two erosion processes are linked as fluvial erosion of the bottom of the bank creates a steeper bank angle or overhanging soil blocks which are more unstable and likely to collapse.
VEGETATION
Vegetation can have a significant impact on bank erosion. Banks with vegetation erode slower than those without. Dense vegetation growing on the bank face can deflect flowing water and prevent fluvial erosion. Roots generally increase the strength of bank material, making a bank less prone to mass failure. However, trees can also add significant weight to the tops of stream banks and may actually decrease stability.
references
https://www.dep.state.pa.us/
https://en.wikipedia.org/wiki/Bank_erosion
https://www.preventionweb.net/
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