April 21, 2014
A long vacant tract of land in Overland Park, Kansas along a primary commercial corridor is being evaluated for a mixed use development named City Place. The site, located at College Blvd. and US 69 Highway, has an ephemeral channel draining through it that conflicts with several required infrastructure features. The US Army Corps of Engineers has identified the channel as degraded, opening the possibility for channel relocation and enhancement. Terra Technologies Inc. is working with the Corps to determine Clean Water Act permitting requirements for the development and performed a geomorphic channel assessment to determine the requirements for any channel relocations.
Existing and proposed hydrology will substantially differ so the existing channel form was not a reliable reference. Unfortunately, no stable reference streams of a similar magnitude exist nearby since most channels of this magnitude are typically piped or altered when properties are developed and the development fringe for the area is many miles away. Therefore, the existing and proposed channels had to be evaluated based upon ranges of geomorphic parameters that are generally considered stable for the given stream types. The existing channel had been modified by the historical construction and then later breaching of a pond midway across the parcel while the hydrologic changes due to development of the watershed were just beginning to be reflected in the channel form. The geomorphic assessment predicted potential down cutting of the channel bottom elevation at the upstream end of 6 to 8 feet, a transition that would certainly impact adjacent property and infrastructure.
Due to continued negotiation with the City regarding the final development form, the proposed channel constraints are still unknown so only the general channel requirements can be determined at this stage. A 1% channel gradient is anticipated to be stable vertically and will be provided through a combination of longer channel length by increasing sinuosity and rock grade control weirs that will mimic natural subsurface rock outcroppings. Final channel design will be performed once all the parameters and constraints are determined.
For more information about geomorphic analysis and assessment, please contact your local Terra Technologies office.
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