March 15,2013
The Smith Creek Wetland and Stream Mitigation Bank endeavored to restore several historical ephemeral channels that had been removed by past farming practices. The regulatory agencies involved had asked for additional information to justify the design and construction of these streams so Terra Technologies Inc. performed a geomorphic assessment of these channels to determine if they are likely viable features that can be self-sustaining and self-maintaining moving forward.
The drainage area and hydrology for each channel was evaluated in comparison to the channel horizontal and vertical alignments and form. Hydraulic modeling calculations were then performed to assess depths of flow and velocities at various return interval events and the associated sediment carrying capacities of the channels for each return interval evaluated. The channels were then compared to “ideal” criteria as defined by the Rosgen Stream Classification System and the geomorphic criteria range for each defined stream type.
Analysis results revealed the channels are viable ephemeral channels within or very close to the accepted design standards but some are expected to evolve further to be self-maintaining, self-sustaining features. In general, the previously constructed channels were too small in cross section. Over time the channels will create the required form naturally or the process can be accelerated mechanically with earth moving equipment. Some topographical deficiencies were noted that allow the channels to take undesired paths, and these have been corrected. The results have been submitted for review by the regulatory agencies.
For more information about geomorphic analysis and assessment, please contact your local Terra Technologies office.
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