Wadeable stream habitat monitoring at Chattahoochee River National Recreation Area: 2021 change report

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. Streams chosen for assessment were specifically targeted for management interest or to provide a context for similar-sized stream(s) within the park. This report describes the status and trends of in-stream and riparian habitat conditions in 13 wadeable stream reaches at Chattahoochee River National Recreation Area (CHAT) between two survey periods (2017 and 2021). In-stream habitats were primarily characterized by high-energy conditions, dominated by riffles and runs. A decline in pool habitat was observed in many reaches, reducing habitat complexity and limiting aquatic organism diversity. Additionally, fine sediment deposition was noted in several reaches, which negatively impacts aquatic life and water quality. Large woody debris (LWD) played a crucial role in creating diverse habitats and stabilizing streambanks. However, LWD dynamics, including recruitment and retention, varied among reaches. Geomorphic processes, such as bank erosion, channel incision, and knickpoint migration, were evident in many reaches. These processes were linked to historical land use practices and ongoing disturbances, such as urbanization and altered hydrology. All the monitored stream reaches are recovering from a legacy of poor land use and responding to varying amounts of impervious surface cover in their watersheds. The streams at Chattahoochee River National Recreation Area display characteristics of streams in Stage III (widening via bank slumping) or Stage IV (aggradation and planform adjustment) of stream evolution (Schumm et al. 1984) as they work to establish a new equilibrium following the above-mentioned land use impacts. Management concerns included trail erosion, mass wasting, infrastructure damage from treefalls, and sediment delivery from adjacent hillslopes. Trail erosion can degrade visitor experiences and increase maintenance costs. Treefalls have contributed entire trees to one stream channel, and while LWD is beneficial for habitat, entire mature trees may pose risks to downstream infrastructure, particularly if mobilized during high-flow events. Sediment delivery from hillslope upstream erosion can degrade water quality, smother benthic organisms, and fill in pools. Continued monitoring and potential management interventions, such as LWD placement, bank stabilization, and sediment source control, may be necessary to mitigate these issues and maintain the ecological integrity of these valuable stream ecosystems. Further research on flow regime and macroinvertebrate community structure is necessary to better understand how these streams and associated habitat are changing through time.