Historical analysis of the relationship of streamflow flashiness with population density, imperviousness, and percent urban land cover in the Mid-Atlantic region

摘要

Historical US Census population data was used to estimate populationdensity for 1930-2000 and satellite imagery from circa 1973, 1992, and 2001 wasused to estimate the degree of urban development and the percent imperviousness (for1992 and 2001) for a set of 150 small (< 130 km~2) watersheds with long-term (> 20years) USGS NWIS historical daily mean streamflow datasets in the mid-Atlantic,USA. The Richards-Baker Flashiness Index was used to calculate annual flashinessvalues and a seven-year-window mean stream flashiness value was calculated foreach population/development estimation date. Streamflow stations that showedsignificant changes in historical flashiness had a higher mean population density thanthose that showed no change. The strength of the population-flashiness correlationincreased as the spatial scale of the population estimator was reduced. Urbandevelopment and imperviousness estimators were equally effective at exploring therelationship between stream flashiness and watershed development. Watersheds withless than 10% imperviousness and less than 20% 'urban development' displayedbackground levels of stream flashiness and mean flashiness increased with increasingimperviousness and urban development density thereafter.