Abstract

Flooding can have negative effects on stream health by increasing pollution and sediment, disturbing the natural flow regime, and removing vegetation. On September 27th, 2024, Tropical Storm Helene delivered large amounts of rainfall across Western North Carolina, causing major flooding and riparian damage. This project evaluated the health of streams in the Swannanoa River watershed before and after Helene using macroinvertebrates and water temperature data. Macroinvertebrates are commonly used as biological indicators because they are abundant, easy to sample, and sensitive to stream quality. Macroinvertebrate samples were collected from four forested and four non-forested streams using a Surber sampler at eight randomized points from riffles and pools, and water temperature was measured from May through September. To assess stream health, macroinvertebrates were identified to family, and a Family-Based Index of Biotic Integrity (FBIBI) and percent of insects belonging to the orders Ephemeroptera, Trichoptera, and Plecoptera (EPT) were calculated. Of the eight stream sites, two were significantly affected by Helene as FBIBI increased significantly at Burgin Cove and Flat Creek, and %EPT decreased significantly, indicating a decline in water quality. These two sites were both in the forested stream category. Stream health did not differ significantly at the six other sites. After controlling for air temperature, it was seen that  there was a significant increase in water temperature, possibly due to loss of riparian vegetation. This study showed evidence that some forested streams in the Swannanoa watershed were negatively affected by the impacts of Tropical Storm Helene, which may help focus recovery efforts.

Keywords

Macroinvertebrates, Helene, Water Quality, Stream Ecology, Swannanoa River

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