Abstract
Although recent studies have emphasized the benefits of Low Impact Development (LID), the influence of LID on impervious surface connectivity to downstream drainage has not yet been fully investigated by using quantitative measurements. Some previous studies have attempted to measure correlates between discharged stormwater volume and the directly connected impervious areas (DCIA), a fraction of the impervious area that is hydraulically connected to downstream drainage by a piped route. They found that DCIA could be a more accurate predictor of urban development impacts on stream ecosystems than is the total impervious area. This study measured the DCIA of urban watersheds in the Energy Corridor District, Houston, Texas, where rapid urbanization and increasing impervious surfaces have caused urban stream degradation during the past decades. This study primarily prioritized land use into four types based on the contribution of hypothetically implemented LID facilities to DCIA reduction for each land use. Stormwater infrastructure and impervious cover data were analyzed using Geographic Information Systems. Sutherland's equations taken from Sutherland, R.C. (1995) were utilized to compute DCIA at the parcel level. The results were 1) a greater value of current DCIA in commercial areas than in residential areas (single family houses 40%, multi-family houses 64%, big box retails 77%, scattered small-scale retails 71%); 2) a significant reduction of DCIA for all land uses after hypothetically implementing LID applications (reduction rates ranged from 6.4% to 52.2%); and 3) the greatest change of DCIA in big box retail areas with pervious pavement and vegetated swale installation. The results will contribute to determining which land use type is of higher priority in implementing source-control stormwater infrastructure and providing local governments with a better index to calculate drainage fees, which are currently imposed on property owners based on total impervious area.
Highlights
Groundwater deficiency is one of the most critical water challenges faced by Texas in recent decades.With an increased frequency and intensity of extreme drought, Texas has experienced a severe reduction in groundwater recharge and surface water supplementation [1]
Current development conditions in/near the Energy Corridor District (ECD) revealed varying imperviousness connectivity depending on land use types
directly connected impervious area (DCIA) refers to a subset of the total impervious area (TIA) which is directly connected to downstream drainage by underground stormwater pipelines
Summary
With an increased frequency and intensity of extreme drought, Texas has experienced a severe reduction in groundwater recharge and surface water supplementation [1]. Projections indicate that by 2040 the population will double in Montgomery County, Texas, causing groundwater use by human activities to exceed the capacity of the Gulf Coast aquifer recharge [2]. There was an approximate 40% increase in urban surface in the Houston Metropolitan Area between 1978 and 2000 [5]. This rapid urban growth has increased urban stormwater runoff drained by Buffalo Bayou and organic and nutrient loading in major tributaries [6, 7]
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