Riparian Vegetation Influence on Channel Widths of Small Streams: Revisiting Sleepers River

Restoration of riparian, or streamside, forests has become a major focus of watershed initiatives throughout the United States as a means for improving water quality, temperature regimes, and in-stream physical habitat. Despite these benefits, the influence of riparian vegetation on stream channel width is not fully understood. One of the earliest studies on this topic found that channel bed widths were larger in reaches with forested riparian vegetation than in reaches with "sod," or grassy riparian vegetation along the same stream. Our study offers a unique opportunity because it capitalizes on a historic data set collected in the Sleepers River Research Watershed in Danville, Vermont in the 1960s. This historic data set contains hundreds of bed width measurements for several tributaries in the Sleepers River Watershed that once had a diverse patchwork of forested and non-forested riparian vegetation. For example, approximately half of the riparian zone along a small, unnamed stream (W-12) was forested in the mid 1960s with seven distinct forest patches. Today, one large patch of forest occupies nearly 80% of the riparian zone of W-12. Changes in the bed widths of W-12 were evaluated following this 40-year period of riparian reforestation. We revisited approximately 300 locations along W-12 and portions of upper Pope Brook to measure bed widths. Our results were consistent with many studies that have found that forested reaches were wider than non-forested reaches. Furthermore, reaches with recently reforested vegetation have widened since the mid 1960s; however, they were not as wide as reaches that have been forested from at least the 1940s Stream channel widening in response to riparian reforestation may have significant and previously unforeseen consequences for restoration initiatives.