Long-term impact of development on a watershed: early indicators of future problems

Development in the floodplain increases damage from flooding. Development in a watershed also augments the potential for flooding. This study of sustainable development examines the development of a watershed in the greater metropolitan area of Houston, TX, where flooding has become a major issue and intervention by planners has been minimal. This article examines the impact of land development in a closed watershed over a 50-year period. Daily flow data from the United States Geological Survey (USGS) are combined with daily precipitation data from the United States National Oceanic and Atmospheric Administration (NOAA) to estimate the precipitation-adjusted annual streamflow. Annual development data from the Harris County Appraisal District (HCAD) are combined at the parcel level and used to analyze the relationship between land development and outflow. The results lead to an enhanced understanding of the mechanisms that result in increased flooding and an ability to use planning tools and policies to control development more effectively to avoid watershed problems years before these problems become apparent. While impervious cover is important in determining the impact of development on watershed function, impervious cover alone is not sufficiently sensitive to guide development decisions that impact the long-term future of the watershed.