Olsson Associates (OA) contracted the Ozarks Environmental and Water Resources Institute (OEWRI) at Missouri State University to complete a geomorphic assessment of the channel network within Upper Indian Creek watershed in Olathe, Kansas. In this study, the field-based channel survey used is specifically focused on stream related problems involving public infrastructure and private property of a highly urbanized watershed. The assessment is designed to not only locate “problem” areas, but to also identify the causes of those problems. This study focused on the upper 11 mi2 of Indian Creek that generally flows northeast from the City of Olathe from Avalon Street to Pflumm Road. The main channel of Indian Creek had the highest number of problems, but the tributaries have the highest density (problems per stream mile) of problems. In total, 5.2 miles of main channel and 9.6 miles of tributaries were evaluated for this project and 188 problems were identified and located. There were 55 problems located on the main channel, for a density of about 10 problems per stream mile. For the tributaries, there were 133 problems located for a density of nearly 14 problems per stream mile. This suggests the tributaries in this watershed appear to be changing more rapidly and offer more challenges in terms of infrastructure maintenance and protection than the main channel. The highest density of problems came from tributaries 7 and 8 (T-7 and T-8) west of Mur-Len Road and north of 135th street with >50 problems per stream mile. Impervious surfaces associated with urban land use have decreased infiltration capacity of the soil and increased the magnitude, duration and frequency of floods. Indian Creek and its tributaries have responded to the increase in flows by getting larger overall and locally unstable. Results of the main channel assessment suggest bank erosion is the major process creating infrastructure problems along the main channel as it appears bedrock is limiting incision along much of the channel. Channel incision along a series of head cuts moving upstream is the major process impacting public infrastructure and private property along the tributaries within the Indian Creek watershed. Additional study of geomorphic stability in Indian Creek should focus on the causes and rates of head cutting in the tributaries and the lateral rates of channel erosion in the lower segment with attention to the causes and bedrock control of bluff failure due to bank erosion.

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Final report to Olsson Associates for the City of Olathe, Kansas

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