Wadeable stream habitat monitoring at Horseshoe Bend National Military Park: 2019 baseline report

McDonald, Jacob

doi:10.36967/2271740

The Southeast Coast Network (SECN) stream habitat monitoring protocol collects data to give park resource managers insight into the status of and trends in stream and near-channel habitat conditions (McDonald et al. 2018a). Wadeable stream assessments are currently implemented at the five SECN inland parks with wadeable streams: Horseshoe Bend National Military Park (HOBE), Kennesaw Mountain National Battlefield Park (KEMO), Ocmulgee Mounds National Historical Park (OCMU), Chattahoochee River National Recreation Area (CHAT), and Congaree National Park (CONG). Streams chosen for assessment were specifically targeted for management interest (e.g., trail erosion issues and upstream urban development) or to provide a context for similar-sized stream(s) within the park or network (McDonald 2019). The objectives of the SECN stream habitat monitoring protocol are to: • Determine status of upstream watershed characteristics (basin morphology) and trends in land cover that may affect stream habitat. • Determine the status of and trends in benthic and near-channel habitat in selected wadeable stream reaches (e.g., bed sediment, geomorphic channel units, and large woody debris). • Determine the status of and trends in cross-sectional morphology, longitudinal gradient, and sinuosity of selected wadeable stream reaches. On April 24, 2019, data were collected at Horseshoe Bend National Military Park (HOBE) to characterize the in- and near-channel habitat on a permanently monumented reach on a second Strahler stream order stream (Strahler 1957) nicknamed “Claybed Creek” (HOBE001). These data, along with analysis of remotely-sensed geographic information system (GIS) data, are presented in this report to describe and compare the watershed-, reach-, and transect-scale characteristics of HOBE001 to selected second-order streams at Chattahoochee River National Recreation Area (CHAT004, -008, -010, and -014). Though the historic and contemporary land use/land cover in the watersheds draining to HOBE001 and the CHAT streams are very different (and thus the streams are expected to be significantly different) these comparisons are included to provide a context for the survey at HOBE001. HOBE001’s watershed (“Claybed Creek”) has high basin shape and moderate slope/relief and is covered by forest, pasture, and shrubland. The major defining characteristics of the stream were the presence of claybeds in the bed of the stream, a groundwater seep along one side of the stream, and floodplains along both sides of the stream. Based on the different geomorphic surfaces observed within and immediately surrounding the reach, the stream appears to be in channel evolution model (CEM) stage III. The floodplain surfaces are interpreted as evidence that the stream is widening (common characteristic of CEM stage III) through progressive slumping of the stream banks. The presence of the claybeds within the reach could potentially disrupt progression along the channel evolution continuum due to its high rate of erodability. Should a knickpoint (large change in slope) migrate upstream into the reach, these exposed claybeds would not provide sufficient protection of the channel bed. This knickpoint could migrate upstream relatively quickly and set the stream back in its evolutionary stage. The rate at which this knickpoint migrates upstream is dependent on the sediment composition of the boundary layer (bed sediment), the amount of LWD available to increase bed and bank resistance, and the flow regime that shapes the stream. With regard to habitat, the distinguishing features of the stream were the homogeneity of geomorphic channel units (predominately run) and the lack of large woody debris (LWD) within the reach. While the reach lacked fine and very fine sediment in its representative riffle (where the pebble count was conducted), the lack of cobble-sized particles within the reach increases the potential for increased bed mobility if a large flood event affects t

Wadeable stream habitat monitoring at Horseshoe Bend National Military Park: 2019 baseline report

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