ABSTRACT
The incursion of residential and commercial development into terrestrial habitats is resulting in measurable changes to the composition and pattern of landscape and affects watershed hydrology. Monitoring of land-cover change and study of the effects of increasing impervious surface areas (ISAs) and declining forest cover as a result of suburban development are critical to the quantifi cation of the state of, changes in, and anthropogenic threats to surface runoff-a major contributor to coastal waters. ISA is defi ned as any impenetrable material that prevents infi ltration of water into the soil. Urban pavements, such as rooftops, roads, sidewalks, parking lots, driveways, and other man-made concrete surfaces, are among impervious surface types that feature the urban and suburban landscape. ISA is a critical factor in cycling of terrestrial runoff and associated materials to and within ocean margin waters. Increasing ISA impacts watershed hydrology in terms of infl uencing the runoff and basefl ow. Urban
runoff, mostly over the impervious surface, is the leading source of pollution in the Nation’s estuaries, lakes, and rivers (Arnold and Gibbons, 1996; Booth and Jackson, 1997). Runoff frequently contains high concentrations of nutrients and pollutants, which can be harmful to freshwater and marine organisms, and therefore, it has signifi cant impacts on sensitive tidal creeks and estuary systems (Schiff et al., 2002). The ISA has emerged as a key indicator to explain and predict ecosystem health in relation to watershed development. A published watershed-planning model predicts that most stream quality indicators decline when the watershed ISA exceeds 10% (Schueler, 2003). Assessment of the quantity of ISA in landscapes has become increasingly important with growing concern of its impact on the environment (Weng, 2001; Civco et al., 2002; Dougherty et al., 2004; Wang and Zhang, 2004). This is true even for coastal watersheds where continental shelves, inland or partially enclosed seas, estuaries, bays, lagoons, beaches, and terrestrial and aquatic ecosystems within them that drain into coastal waters. Human activities in urbanized coastal areas deliver sewage, solid wastes, refuse, sediments, dust, pesticides, and hydrocarbons to coastal rivers, estuaries, and the oceans. It is estimated that about 80% of all marine pollution originates from land-based sources and activities (Costa-Pierce, 2006). Assessing landbased sources of pollution to coastal oceans and how to mitigate and rehabilitate the impacts on coastal ecosystems are receiving growing attention. Precise data on ISA in spatial coverage and distribution patterns in association with landscape characterizations are critical for providing the key baseline information for effective coastal management and improved decision-making.
