Science Inventory

CONFIRMING THE RESULTS: AN ACCURACY ASSESSMENT OF REMOTE PRODUCTS, AN EXAMPLE COMPARING MULTIPLE MID-ATLANTIC SUB-PIXEL IMPERVIOUS SURFACE MAPS

Citation:

JENNINGS, D. B. AND S. JARNAGIN. CONFIRMING THE RESULTS: AN ACCURACY ASSESSMENT OF REMOTE PRODUCTS, AN EXAMPLE COMPARING MULTIPLE MID-ATLANTIC SUB-PIXEL IMPERVIOUS SURFACE MAPS. Presented at EPA Regional Science Applications Seminar, Dallas, TX, March 02, 2005.

Impact/Purpose:

Overarching Objectives and Links to Multi-year Planning

This research directly supports long-term goals established in ORD's multi-year research plans related to GPRA Goal 2 (Water Quality) and Long Term Goal WQ-2 Assessment of aquatic systems impairment. Relative to the GRPA Goal 2 Water Quality multi-year plan, this research will "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors" and "provide the tools to restore and protect aquatic ecosystems and to forecast the ecological, economic, and human health outcomes of alternative solutions" (Water Quality Long Term Research Goals 2 and 3).

Subtask 1 - Impervious Surface Evaluation

This subtask addresses the development of impervious surfaces estimators for local to regional scale assessments of watersheds and their landscape relationship to stream ecology. The amount of impervious surface area in a watershed is a key indicator of landscape change. As a single variable, it serves to integrate a number of concurrent interactions that directly influence a watershed's hydrology, stream chemical quality, and in-stream habitat. It is our working hypothesis that impervious surface area within a watershed, as an independently mapped predictor variable, can be used to generally track a range of watershed ecological parameters (e.g., NPS pollution, biological integrity, TMDLs) that are of concern to local, state and federal environmental managers. The specific objectives of this research are: 1) to quantitatively evaluate the varying remote sensing methods used in mapping impervious surfaces at multiple scales (local to regional), and 2) to relate the varying levels of impervious surface area in watersheds to the environmental condition of multiple water resource endpoints such as streamflow, temperature, and biota.



Subtask 2 -- Landscape Assessments and Evaluations of Best Management Practices: Watershed Demonstrations

Best Management Practices (BMP) encompass a range of strategies to reduce water pollution related to urban and agricultural activities. EPA, through Section 319(h) of the Clean Water Act [PL 92-500], provides grants to states to implement BMPs in areas with suspected or known water-quality problems. Grants for implementation of BMPs have not been tracked or monitored to document their effectiveness. Although effectiveness can be measured in many different ways, one straightforward but important measure is existence. Implementation of BMPs is a voluntary process and actual implementation is not always executed (Nowak 1992). The primary objective of this project is to assess the feasibility of using high-resolution aerial photography and other remotely sensed data to identify the existence of BMPs that were planned under the 319 program. An additional objective is to evaluate the effectives of BMPs implemented by examining monitoring data from about 5 sites in the OW National NPS monitoring system.

There are several potential benefits to determining the feasibility of using the aerial photography for identifying BMPs: 1) since BMP implementation is voluntary and some may not be implemented due to a variety of social and economic factors (Nowak 1992), remote detection of BMPs can provide data to estimate the ratio of BMPs implemented to BMPs planned; 2) remote detection of BMPs provides validation data that can be input into EPA's Grants Reporting and Tracking System (GRTS), and 3) remote monitoring of BMPs over time could be used to develop data on BMP lifespans, providing important data related to social- and cost-effectiveness.

Subtask 3 -- TMDL Non-point Source Assessment Tool

This subtask involves the development of a software tool to assess the potential risks of water bodies to exceed TMDL threshold values established by States. When completed, the tool will allow the user to evaluate watersheds over entire regions. The too

Description:

Anthropogenic impervious surfaces have an important relationship with non-point source pollution (NPS) in urban watersheds. The amount of impervious surface area in a watershed is a key indicator of landscape change. As a single variable, it serves to intcgrate a number of concurrent interactions that directly influence a watershed's hydrology, stream chemical quality and thus the in-steam habitat. Although, numerous research efforts have explicitly mapped impervious surface at the local scale, using high-resolution remote sensing source. Few studies have attempted to explicitly map the variable at the regional scale using medium remote sensing sources such as Landsat imagery. Recent image processing advances have allowed impervious surface area to be mapped at the Landsat sub-pixel level and several Landsat sub-pixel mapping efforts in the mid-Atlantic region have been undertaken. The problem for the environmental community is at what level of accuracy these sub-pixel maps portray impervious surfaces and at what scale these maps can be adequately utilized?

A "truth" mapping protocol as set forth in the United States Geological Survey (USGS) prospectus "Shared assessment of USGS and NGO impervious surface data-sets for the Chesapeake Bay Watershed" will be implemented to create a set of 600 truth" impervious surface chjps derived from high spatial resolution imagery. A USEP A peer-reviewed accuracy assessment (AA) protocol has been established which will be the basis for testing the sub-pixel impervious surface maps of the mid-Atlantic region produced by the USGS, University of Maryland, College Park, and Towson University respectively. Our research partners are the USGS National Mapping Division (NMD) in Reston, Virginia. The Chesapeake Bay Program in Annapolis. Maryland as well as the University of Maryland, College Park and Towson University I in Baltimore, Maryland.

The requestor and primary user of the accuracy assessment results will be the Chesapeake bay Program where it is necessary to know the statistical uncertainty, at multiple spatial scales involved with the data. However, all users of landscape data -loca1 to Federal and NGOs within the Chesapeake Bay watershed will apply the results of the AA. Additionally, The NLCDOO mapping program will also use the results to determine the relevance of their national level sub-pixel mapping program.

Record Details:

Record Type:DOCUMENT( PRESENTATION/ ABSTRACT)
Product Published Date:03/02/2005
Record Last Revised:06/21/2006
Record ID: 114967