Mitigation Solutions
We tested 5 different mitigation scenarios to determine if implementation would increase flow through the system. On the right are the 5 solutions.
However, after taking into account the benefits generated, as well as the costs involved with the various proposed solutions, we decided to concentrate on the stretch of the river leading up to the bridge at Bridge Rd.
Dredging is a rather cheap option, that will not impact the surrounding infrastructure. Whereas removing or widening a bridge can incur substantial costs, both in terms of money, as well as road user costs.
However, regardless of potential costs, we analyzed to whether or not implementing any of these 5 solutions would help increase flow through the system.
After running these 5 scenarios through our HEC-RAS model, we decided to concentrate on dredging the channel leading up to the crossing at Bridge Rd.
After testing various dredging scenarios, the largest increase in flow rate resulted from the following dredging characteristics:
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Dredging the 800-900' leading from channel inlet through bridge road
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1-4’ of dredging to create more uniform trapezoidal cross sections
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Average bottom elevation of about 841’ (STA 89539 - STA 88606)
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The table below summarizes the percent change from the existing delivery curve to the post dredging delivery curve. Notice the average increase in flow rate is between 10-18%, which satisfies our overall goal of increasing flow rate between Lake Monona and Lake Waubesa.
Channel widening at the railroad trestle
1.
Channel Widening at Bridge Rd.
2.
Dredging leading up to the railroad trestle
3.
Removing railroad trestle and bridge at Bridge Rd.
4.
Dredging from mouth of river to Bridge Road
5.
