GIS Tool Used in Portsmouth to Model Stormwater Runoff

Hodgson Brook Watershed and North Mill Pond to Benefit
Portsmouth, New Hampshire – July 22, 2014 – Earlier this spring, Pamela Ordung, a recent Penn State graduate and GIS Technician for Tighe & Bond, presented her capstone project at Great Bay Community College to representatives of Hodgson Brook Advisory Board, Advocates for North Mill Pond, the New Hampshire Department of Environmental Services, the city of Portsmouth GIS department, and the University of New Hampshire.  The project involved development of a Geographic Information System (GIS)-based tool to model stormwater flows to the Hodgson Brook.

The Hodgson Brook watershed is an impaired watershed that covers approximately 20% of the total land area in Portsmouth, New Hampshire.  Nearly 55% of this watershed falls within the Pease International Tradeport, a former air force base, and 32% is covered by impervious surfaces.  These impervious surfaces contribute to contamination of Hodgson Brook by rapidly directing stormwater runoff from streets, parking lots, and buildings directly into the brook and surrounding wetlands.  Pollutants can include metals, organic chemicals, and nutrients.

Several stormwater management and treatment practices are currently used within the Tradeport and surrounding watershed, including rain gardens, stormwater treatment wetlands, gravel wetlands and pervious pavement.  The Pease Golf Course parking lot was recently reconstructed with pervious pavement.

Ordung’s work involved dividing the Hodgson Brook watershed into sub-watersheds based on recent Light Detection and Ranging (LIDAR) elevation data that was collected for the region and modeling storm water surface flow using ESRI’s GIS ArcHydro software.  Once an efficient methodology was established, Ordung created a repeatable model using ESRI’s ArcGIS ModelBuilder.  Using Ordung’s application, a user can define an impervious surface area and the model predicts where the stormwater will flow.

This modeling effort improves the ability to monitor stormwater flow, and will facilitate the implementation of future stormwater management techniques throughout the watershed by pin-pointing areas that may be contributing to the pollution of the brook.  With continued monitoring and use of this tool by various stakeholders, the goal is to create improved stormwater management plans for existing and new development.  Project stakeholders and potential users of Ordung’s model include the Hodgson Brook Advisory Board, Advocates for the North Mill Pond, tenants of the Pease International Tradeport, and the City of Portsmouth, NH.  Other cities, towns and watershed groups in New Hampshire can benefit as well and easily build a similar application for their communities.


Hodgson Brook Advisory Board
The Hodgson Brook Advisory Board (HBAB) is composed of representatives from organizations found in the watershed.  The HBAB was formed to ensure that this effort includes anyone who has a stake in the health and safe enjoyment of Hodgson Brook and the North Mill Pond. The HBAB members bring a wide range of views and perspectives as well as a wealth of professional knowledge. Business leaders, engineers, transportation and management specialist, citizens, environmental specialist, water quality specialist, research scientist, and estuarine scientist are represented on the HBAB. The HBAB meets quarterly.

The HBAB works together to improve water quality and natural habitat by creating and implementing a restoration plan that builds community support through education. The plan includes input from watershed residents and business owners, the best science available, and promotes ecological integrity and long term stewardship. The Hodgson Brook Restoration Project is funded through in part by a Watershed Assistance Grant from the NH Department of Environmental Services with Clean Water Act Section 319 funds from the U.S. Environmental Protection Agency.


Tighe & Bond
Pam Ordung works for Tighe & Bond.  Founded in 1911, Tighe & Bond is one of the most experienced engineering firms in New England, with offices in Portsmouth at Pease; Pocasset, Westfield, and Worcester, Massachusetts; Middletown and Shelton, Connecticut. Engineering News Record annually ranks Tighe & Bond among the top design and environmental engineering firms nationally.  ZweigWhite also has recognized Tighe & Bond several times as one of the best engineering firms to work for in the nation.  With a team of more than 240 employees, Tighe & Bond provides engineering, environmental consulting and GIS services to clients in government, industry, healthcare, education, real estate, energy, and water/wastewater markets.