Science Serving Maryland's Coasts

R/WS-1a

Investigating impacts of headwater stream burial during development on downstream nutrient export to Chesapeake Bay

Principal Investigator: 

Andrew Elmore

Start/End Year: 

2009 to 2012

Institution: 

University of Maryland Center for Environmental Science

Co-Principal investigator: 

Sujay Kaushal, Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science; Jason Jullian, University of Oklahoma

Strategic focus area: 

Viable coastal communities and economies

Description: 

*This project is a continuing project initially funded through award NA05OAR4171042 (year one) and currently funded through award NA10OAR4170072 (year two)*

OBJECTIVES: We will investigate three questions related to the emerging problem of buried streams (paved over stream channels, and streams in culverts and storm water drains) and their impact on the forms, fluxes, and transformation of nitrogen delivered to Chesapeake Bay: (1) Where are the headwater streams in Maryland? (2) What is the present extent of stream burial as a function of urban land use change? (3) What is the effect of stream burial on ecosystem functions and nitrogen export to coastal receiving waters? Working with Maryland Department of Natural Resources (DNR) and the City of Baltimore, our results will inform ongoing stream management and restoration efforts.

METHODOLOGY: At the scale of the state of Maryland, we will map all headwater streams and estimate stream burial extent for all stream sizes. Hydrologic modeling will be used to calculate flow paths from a digital elevation model and, based on field observations, a statistical model of the drainage area at channel initiation. Then, we will use a multivariate classification tree and maps of impervious surface area to calculate the extent of stream burial for 1975, 1990, 2000, and 2005. All products will be rigorously validated. Finally, field data and maps of stream burial within the Gunpowder-Patapsco River watershed will be used to quantify and predict the forms, fluxes, and transformations of nitrogen delivered to the Chesapeake Bay using existing data on stream water quality.

RATIONALE: Coastal development threatens the ecological services provided by headwater streams through stream burial and other forms of impairment. To understand the ecological functioning of Chesapeake Bay, we must look to the watershed, the ultimate source for water, nutrients, and sediments. The project would provide significant benefits to land-use planners in the state of Maryland who seek to protect headwater stream resources and reduce nutrient export to the Chesapeake Bay. A map of headwater streams (buried and intact), and alternate scenarios for stream burial, will be made available for prioritization of stream conservation and restoration efforts. Collaborators on this work include resource managers at the Maryland DNR, the Maryland Association of Floodplain and Storm Water Managers, the US Forest Service, the City of Baltimore, and local watershed societies.

Impact/Outcome: 

This section describes how this project has advanced scientific knowledge and/or made a difference in the lives of coastal residents, communities, and environments. Maryland Sea Grant has reported these details to the National Oceanic and Atmospheric Administration (NOAA), one of our funding sponsors.

SUMMARY: University of Maryland researchers built a novel, detailed map showing streams in a large region of Maryland not recorded on other maps. The new map, which identifies small and buried streams west of the Chesapeake Bay, provides a tool that can help efforts to protect streams from development and to improve water quality in the Chesapeake Bay.

RELEVANCE: Streams, especially small ones, can play an important role in improving water quality, a key goal in the Chesapeake Bay watershed. A healthy stream ecosystem can remove excess nutrients, sediment, and other contaminants from water before it flows into the Bay. However, many streams in Maryland have become filled in and buried by construction and development. Knowing the locations of buried stream channels is relevant to planning projects to unbury and restore them. A detailed map of stream channels is also relevant to protecting not-yet-buried streams from development.

RESPONSE: This project was led by Andrew Elmore of the Appalachian Laboratory of the University of Maryland Center for Environmental Science. He and his colleagues created a computer model predicting where Maryland’s network of streams would be located if all of the state west of the Bay resembled the state’s remaining forests. The map combines information about the known locations of 253 stream headwater zones in upland, forested areas of Maryland. The researchers combined this information with other, statewide data about terrain slope and soil characteristics that can indicate the presence of streams.

The resulting map (http://streammapper.al.umces.edu/) identifies a network of stream channels that is up to 2.5 times more dense than the network shown on maps based on a widely used, nationwide database about surface waters, the National Hydrography Dataset (NHD.) Of the predicted stream locations in Elmore’s model, 84 percent were correct, higher than the NHD’s accuracy rate of 55 percent.

RESULTS: In 2013 Elmore and his colleagues published a description of the model in the journal PLoS One. Officials in several Maryland counties are interested in using the map to help them comply with the new rules called TMDLs (Total Maximum Daily Loads) intended to improve the Bay's water quality. For example, the map could help inform where to plant streamside buffers of trees to help remove nutrients and sediments from runoff. In addition, the Maryland Department of Natural Resources says it may incorporate Elmore’s data into its next update of the maps used to create its GreenPrint tool, a statewide map that identifies lands and watersheds as priorities for conservation because of their high ecological value.

Related Publications: