Where the runoff begins: rethinking the role of impervious area in urban stormwater management

Information on watershed imperviousness has been widely used for assessing the hydrologic and environmental impacts of urbanization, developing urban hydrologic and water quality models, and designing stormwater management strategies ranging from drainage charge to green infrastructure across the world. The description of watershed imperviousness has relied on the concepts of total impervious area and effective impervious area.

Both of these are lumped and static measures that emphasize the extent of imperviousness, but they lack consideration of the spatial pattern of various impervious surfaces. This knowledge gap affects the reliability of hydrologic models that tend to conceptualize pervious and impervious surfaces as two lumped components with no interactions. This project aims to answer: 1) How do spatial heterogeneity and hydrologic connectivity of impervious surfaces affect stormwater runoff in small urban watersheds? 2) How can the understanding of this mechanism benefit the modeling of stormwater runoff?

This project conceptualizes the impervious source area (ISA) of stormwater runoff as a combination of a constant component and a dynamic component with its hydrologic connectivity affected by pervious surfaces. The research methods highlight the use of small uncrewed aircraft systems (UAS) in land cover classification and flow direction analysis with centimeter-level spatial resolution.

Using Corpus Christi in south Texas as an urban laboratory, the project efforts will consist of seven interlinked research tasks across three phases, starting with aerial and ground data collection, transitioning into the progressive characterization of ISA through an integrated geospatial-hydrologic framework, and culminating in the development of a new three-component CN model that can utilize remote sensing data at different levels. The findings of this project will lead to a spatially explicit understanding of the effect of impervious surfaces on stormwater runoff processes and provide an improved scientific basis for developing reliable stormwater management strategies.

Undergraduate students will be integrated into the research team. TAMU-CC is a predominantly minority serving university and this project will provide URM undergraduate and graduate students in these programs with a variety of training and learning opportunities, which will serve TX workforce needs in the areas of water resources and civil engineering.

The project team will participate in TAMU-CC's UAS Summer Camp program that aims to train local high school students and promote their interest in STEM fields related to UAS research. Scientific data and tools of this project will be disseminated through an interactive online platform developed using WebGIS and Google Earth API techniques. The project team will produce a set of videos to introduce the use of UAS and remote sensing in engineering hydrology and stormwater management.

The project team will collaborate with the City of Corpus Christi to enhance its stormwater education program.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.