A recent study by the U.S. Geological Survey (USGS) found that sensitive species loss can occur during the earliest stages of urban development. In addition, there is no single factor responsible for stream degradation. Previous though was that stream systems are resilient up to certain levels of impervious cover (typically 0–10%) within a watershed. However, this study shows that streams are actually much more sensitive, with sensitive species loss occurring with relatively small increases in impervious cover. The study looked at nine metropolitan areas across the U.S., and USGS also developed a modeling tool for determining the best actions for reducing certain stream stressors. The tool, known as the Biological Conditional Gradient (BCG), is based on conditional probability to improve the biotic integrity of impacted streams through the use of stream restoration or urban stormwater best management practices.

On Nov. 30, the U.S. presented findings from this study on the effects of urbanization on streams at a briefing presented by the Northeast Midwest Institute and Water Environment Federation, along with congressional hosts U.S. Sen. Benjamin Cardin (D–Md.) and U.S. Rep. Donna Edwards (D–Md.). Read more and check out the corresponding videos.