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Final Report: Using An "Impervious Permit" Allowance System To Reduce Impervious Surface Coverage for Environmental Sustainability
EPA Grant Number: SU831880Title: Using An "Impervious Permit" Allowance System To Reduce Impervious Surface Coverage for Environmental Sustainability
Investigators: Welty, Claire , Fraley, Lisa , Hanlon, Bernadette , Hanson, Royce , Kolb, Nathan , McGuire, Michael P. , Sharkey, Steve , Vicino, Thomas J.
Institution: University of Maryland - Baltimore County
EPA Project Officer: Nolt-Helms, Cynthia
Project Period: September 30, 2004 through May 30, 2005
Project Amount: $8,269
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity, and the Planet (2004)
Research Category: Pollution Prevention/Sustainable Development
Description:
Objective:Current development dynamics and population projections suggest that further decentralized urbanization is likely to proceed into the near future, resulting in the continuing degradation of the physical environment (Cieslewicz, 2002; Kahn, 2000). An important aspect of urbanization is the development of impervious surface coverage (ISC).
ISC is comprised of built surfaces — roads, rooftops, sidewalks and parking lots — covered by impermeable materials that prevent rain and snowfall from infiltrating into the soil. These surfaces negatively affect water quality, biodiversity, stream channel morphology, and habitat structure (Schueler, 1994). With the lack of infiltration caused by impermeability, rainfall runs unnaturally fast into storm water drainage systems and subsequently into nearby rivers, lakes and streams. With its increased speed, power and volume, urban runoff damages stream banks and drastically alters stream flow and channel. This runoff, as it moves, also carries natural and human-made pollutants into the streams, rivers, lakes and costal waters, changes the water temperature and is detrimental to aquatic life.
Limiting the extent of this imperviousness has important social, environmental and economic benefits, particularly when replaced with vegetated spaces. Socially, non- built areas of the urban landscape are vital to individual and community health (Nichol & Blake, 2000), providing opportunities for people to congregate and engage in recreation and physical activity. In an economic sense, a variety of green spaces such as parks, community gardens, recreational open spaces, and natural protected land stimulate commercial growth and promote inner-city revitalization (Trust for Public Land, 1999). Environmentally, measurement of ISC is important as an indicator of stream degradation and habitat loss (Arnold & Gibbons; Schueler, 1994).
The goal of this project was to consider ways to alleviate the negative environmental effects of impervious surface coverage (ISC) by examining a market- based policy alternative to continued urban development. The policy design aimed to encourage developers to limit impervious surface development, create vegetated space, and reduce urban runoff by implementing storm water management practices. We had four main objectives for our research:
- To identify impervious surface coverage for watersheds in Maryland.
- To determine the criteria for designating a “cap” on impervious surface for each watershed in Maryland.
- To evaluate an allowance system for developers that involved the creation of green space or installation of an infiltration system that reduces urban runoff caused by development.
- To evaluate the feasibility of managing an allowance system through a state agency.
Our project carefully balanced elements of people, prosperity and the planet by considering social, economic and physical aspects of environmental integrity. We analyzed the interaction between urban development, market-driven responses, and the reduction of impervious surface coverage for environmental sustainability. This project was successful in three ways: (1) creating a team that was interdisciplinary in nature; (2) utilizing the skills and expertise of Geographic Information Systems (GIS) technology; and (3) applying public policy as an integrative mechanism. Team members with knowledge of GIS technology and spatial analysis were instrumental in measuring impervious surface coverage, an important aspect of our data analysis and results. Impervious surface coverage was measured using LAN DSAT imagery. The team members quantified and created maps of impervious surface coverage for each watershed in the state from 1990 and 2000. We categorized each 12-digit watershed by imperviousness based on Schueler’s (1994) criteria for “impacted,” “non-supporting,” and “sensitive” streams.
The results of our analysis of these ISC maps are quite telling. Foremost, they demonstrate how Maryland’s watersheds have been impacted by urban growth and increased decentralization throughout the region. These results are also quantifiable using geographic information systems (GIS) technology. There is a dramatic increase in ISC along the Interstate 95 and Interstate 70 corridors. The cities of Frederick and Hagerstown grew substantially in the 1990s and, on the Eastern Shore, Salisbury witnessed dramatic outward expansion from its traditional urban core. The number of watersheds that were less than 10 percent impervious shrank by 19 watersheds in the last decade. In comparison, those watersheds that were more than 25 percent impervious increased by 13 watersheds. Percentage-wise, there were 183 watersheds in Maryland that had more than a five percent increase in impervious cover during the 1990s.
While we used LANDSAT imagery with success, we also found it, at 30 meter pixels, to be too coarse to obtain a truly accurate measure of imperviousness in Maryland. Experts in GIS technology recommend researching and establishing a more accurate measure of impervious surface coverage, an important goal of Phase II of this project.
In our interviews with experts in the field and through our analysis of water quality trading, we discovered that there are a number of important variables besides impervious cover that are important considerations in controlling urban runoff. The spatial and temporal distribution of precipitation events, topography, local hydrology and type of development greatly influence the amount of urban runoff. It is not only an issue of impervious cover; therefore, a system that aims to cap impervious surface alone is inadequate.
Conclusions:Based on our findings, we considered capping urban runoff as an alternative to capping of ISC. Again, we encountered a number of logistical and methodological obstacles. Our qualitative analysis found that: (1) pollution knows no political boundaries; (2) the severity of the negative externalities of impervious surface coverage varies by location in the watershed. The costs of assessing the variation of pollution within a watershed are greater than the benefits, and variation creates difficulty in determining the prices for impervious surface credits; and (3)our initial proposal for managing the cap and trade program at the state level is inappropriate since development is a local function. The process of planning, zoning and growth management is based on policy decisions at the local level of government. Traditionally, state involvement in local development issues have been met with political resistance from local private and public actors (March & Olsen, 1989).
Proposed Phase II objectives and strategies:
Impervious surface cover is an accurate predictor of suburban sprawl (McMahon & Cuffney, 2000; Ryznar & Wagner, 2001). And yet, at this time, there is no accurate measure of ISC for Maryland. This project aims to build on our previous work on imperviousness by providing a more accurate measure of ISC than demonstrated in Phase I. We also aim to analyze the impacts of current and historical local planning process on the development of ISC in the Baltimore metropolitan area. Our project, by developing an understanding of the planning process and its consequences on the growth of impervious surfaces, aims to design a local government-based intervention that leads to more sustainable development. Without a better understanding of the policies and planning processes that promote specific development patterns and types of imperviousness, we cannot effectively evaluate the future consequences for the biophysical system. Our more refined measure of imperviousness will be analyzed and examined from a policy perspective, focusing on the planning decisions that led to this development. The team will assess public policy decisions to determine their impacts on the development of ISC. Next, the team will evaluate the options for the creation and implementation of urban development using a formal historical analysis of local planning decisions. High resolution airborne hyperspectral imagery will be classified to accurately characterize impervious surfaces in the Gwynns Falls watershed.
This proposed project will network with the existing project of the Baltimore Ecosystem Study (BES), one of the two NSF-funded urban long-term ecological research sites (LTERs) in the US. The students will also collaborate with the Center for Urban Environmental Research (CUERE), BES and university academic departments of public policy, economics, geography and environmental systems, civil and environmental engineering, and information systems.
Students will continue their collaboration with Dr. Ellen Banzhaf, an international partner from The Centre for Environmental Research at Leipzig-Halle, Germany. The Centre for Environmental Research was established in 1991 as the first and only establishment in the Helmholtz Association of German Research Centres to be exclusively devoted to environmental research. Dr. Banzhaf is a Research Associate in the Department of Applied Landscape Ecology, and she is an expert in remote sensing data.
Other partnerships will be established in the governmental arena. CUERE will build upon its contacts with the Baltimore County Department of Environmental Protection and Resource Management (DEPRM) and the Baltimore County Division of Planning. These local government agencies will provide technical advisory roles to students involved in this project. Mr. Don Outen, the DEPRM Natural Resources Manager, will be a technical advisor on this project.
Journal Articles:No journal articles submitted with this report: View all 3 publications for this project
Supplemental Keywords:Impervious surface coverage, urbanization, remote sensing,
,
Water, Scientific Discipline, RFA, Water & Watershed, Ground Water, Ecology, Wet Weather Flows, Watersheds, Environmental Chemistry, Engineering, runoff, water quality, stakeholders, permitting, coastal watershed, fate and transport, decision model, ecosystem modeling, stormwater drainage, decision making, active control, storm water, pollution identification and control, Storm Water Management Model, community values, contaminant transport, suburban watersheds, pathogens, urban runoff, microbial pollution, non-point sources
Relevant Websites:
www.umbc.edu/cuere 
http://www.beslter.org
Progress and Final Reports:
Original Abstract