Saving The Banks EarthCache
GEO WALKER: After 10 years this one has seen better days...
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Welcome to Mingo Creek Park, one of three county parks in Washington County, PA.
You will need to bring a tape measure... bigger is better.
Directly across from the parking coordinates [N 40 11.975 W 080 01.518] there is a trail head sign for the Hemlock Trail.
No, this is not a lesson on economics. This Earthcache will attempt to illustrate some of the measures used in stabilizing a stream bank. We will look at different solutions that control and minimize the erosion of the stream banks. Stream bank erosion is common throughout the world. A meander, or curve in a stream is one of the best places show the forces of erosion and deposition. The inside portion of the meander is an area of deposition while the outside of the curve is subjected to erosion.
Bank Armor also known as Rip Rap
This is usually composed of large rocks, used concrete or other building debris. It, by design, deflects the force of the water and the erosive power away from a stream bank or structure. The large rocks help maintain and stabilize the slope of the stream bank.
Spur
A Spur is a type of structure built, primarily of boulders, in the channel of the stream. A Spur is used to either, retard, halt, or deflect the water flow. They can be pervious, allowing some water to flow through, or impervious, totally blocking the water, structures. They begin at the stream bank and continue into the stream bed. Their design is to, deflect the current away from the stream bank and minimize the erosion and thus create a change in the flow of the natural channel.
Weir
A Weir is a man-made obstruction used in stream channels. Weirs come in a number of shapes and sizes. Many Weirs are used by hydrologist to calculate stream flow, while other uses are based on controlling aquatic life and environment. For this exercise we will see how Weirs are used to mitigate, or lessen, the effects of natural erosion caused by a stream.
The addition of a Weir will also aid in the prevention of bank erosion by altering or maintaining a stream channel. Weirs can be either a solid or a porous structure. They are designed to maintain or alter the course of a stream main channel or high water flows.
A Vortex Weir is built from bank to bank and is usually low walled. They are normally found in the shape of the letter “V” or “W”. Weirs that point upstream are designed for stabilizing a stream bank. If they point downstream the design is to divert water flow.
QUESTIONS
BRIDGE N 40 11.960 W 080 01.518
What is the length of the bridge railing, the approximate width of the stream?
Why do you think boulders are placed around the bridge supports?
SITE 1 downstream from the bridge N 40 11.954 W 080 01.501
What is this Weir made of?
What letter of the alphabet best represents its shape? a) U b) V c) W d) other
Looking downstream, does the Weir open closer to the a) right bank b) center or c) left bank?
How does this alter the course of the stream?
SITE 2 upstream from the bridge N 40 11.947 W 080 01.524
Does the Spur angle upstream or downstream?
Is this Spur pervious or impervious?
Are there any other noticeable measures here, at the end of the Spur used to deter erosion?
OMIT SITE #2 The Spur is gone... 4/26/18
SITE 3 N 40 11.984 W 080 01.599
What is this Weir made of?
What letter of the alphabet best represents its shape? a) U b) V c) W d) other
Looking downstream, does the Weir open closer to the a) right bank b) center or c) left bank?
How does this configuration create a straight stream channel?
Additional Hints
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Treasures
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