How Big of an Effect Do Small Dams Have? Using Geomorphological Footprints to Quantify Spatial Impact of Low-Head Dams and Identify Patterns of Across-Dam Variation

• DOI: 10.1371/journal.pone.0141210
• Publication Date: 2015-11-05T18:46:00Z
• Authors: Jane S. Fencl; Martha E. Mather; Katie H. Costigan; Melinda D. Daniels
• Keywords: Footprint; Dam removal

Longitudinal connectivity is a fundamental characteristic of rivers that can be disrupted by natural and anthropogenic processes. Dams are significant disruptions to streams. Over 2,000,000 low-head dams (<7.6 m high) fragment United States rivers. Despite potential adverse impacts these ubiquitous disturbances, the spatial on geomorphology ecology largely untested. Progress for research conservation impaired not knowing magnitude dam impacts. Based geomorphic literature, we refined methodology allowed us quantify extent (herein footprint), assessed variation in footprints across within river network, identified select aspects context this variation. Wetted width, depth, substrate size distributions upstream downstream six Upper Neosho River, Kansas, America were measured. Total averaged 7.9 km (3.0–15.3 km) or 287 wetted widths (136–437 widths). Estimates included both (mean: 6.7 243 widths) 1.2 44 Altogether impacted 47.3 (about 17%) mainstem network. differences age, size, location, primary function, sizes individual network relatively similar. The number distance dams, but height, affected footprints. In summary, individually cumulatively altered lotic ecosystems. Both characteristics neighboring For reasons, require different, more integrative, approach management than individualistic has been applied larger dams.