Seasonal Stream Flow Analysis and Channel Stability on Recently Restored Sevenmile Creek - Comparison of Before and After Restoration

Abstract

Sevenmile Creek, located northwest of Helena, Montana had a deeply incised stream channel and altered riparian zone due to historical agriculture influences. Prickly Pear Land Trust began restoration efforts on Sevenmile Creek in the fall of 2017 with a goal of restoring the floodplain and streamside vegetation to positively impact the surrounding ecosystem. The restoration project was divided into four reaches, with upstream Reaches 1 and 2 receiving the least amount of restoration work and were mainly unaltered. Reaches 3 and 4 were the most impacted and incised. In those reaches the old channel was filled and the active channel returned to a more natural form and floodplain. Our study aims to quantify changes in channel form and floodplain before, during and after restoration activity along Reach 4 of Sevenmile Creek. In November 2021, the ES 381 Landscape Analysis class measured four cross-channel profiles along the newly restored Reach 4. These will be compared with similar profiles measured in 2019 before restoration efforts began. Spring floods in 2021 (prior to our fall survey) caused Sevenmile Creek to avulse its new channel in one area encompassed by our survey. The avulsed area was ‘repaired’ in winter 2022. We will conduct several more surveys this spring, before and after spring runoff, to quantify any channel changes and assess the progress and effectiveness of restoration efforts. This study will help assess the success of the restoration project and will allow for a continued examination of the Sevenmile Creek in the coming years.