276-6 Assessment of stream restoration in northern coldwater streams in Minnesota, USA

Session: Natural and Urban Channel Responses to Disturbance, Management, and Restoration

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Stream restoration in northern Minnesota is often done with a goal of improving coldwater fish habitat, with additional goals of improving connectivity and reducing erosion. We investigated six stream realignments in northern Minnesota to see how they functioned following restoration. Specifically, we tracked erosion by combining drone photogrammetry-derived topography from 2024 with aerial lidar in 2021 and measured shifts in habitat structure from repeat habitat surveys over the same period. We compared habitat metrics including pool and riffle lengths, pool to pool spacing, and cross-sectional geometry. Data were collected on treatment reaches that had undergone full channel realignment and matched control sites nearby that had not. Companion projects studied fish and macroinvertebrate abundance, temperature, nutrient uptake, and hyporheic exchange. 

Realignments occurred between 2017 and 2022, with two sites re-meandered after lidar was flown. Two of the study sites experienced large geomorphic changes during the study period. The East Beaver site incised during a rainfall event in May 2022. The Mission Creek site experienced significant erosion in summer 2024. Those were the two largest rivers studied (27 and 129 km2 watershed areas), with reach slopes of 1.38% and 1.41%. Rivers that remained more stable (Chester and Sargent) had upstream areas of 4 km2 and slopes from 0.62% to 1.38%.  The biggest changes were seen at East Beaver: data show both treatment and control reaches had larger cross-sectional geometries and pools, but the treatment site had larger changes. 

Comparing control to treatment reaches, we found significantly less canopy and shading in treatment sites. Riparian canopy > 5m high and densiometer surveys showed lower cover in treatment sites. This is not surprising as many remeandering projects remove woody vegetation during installation. There were no significant differences in understory cover, large woody debris (LWD) abundance, filamentous algae, in-stream root cover, and macrophyte cover between treatment and controls, when mean values were compared across all streams. LWD was much lower at every treatment site except Mission Creek, which was explained by extensive additions of toe wood there. Data from companion projects show higher temperatures in treatment sites compared to control sites. These results highlight the challenges of channel reconstructions in northern climates, where vegetation recovers slowly and riparian cover plays an important role in maintaining cool temperatures.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7795

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