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Mapping Data and Methodology

An overview of the mapping data and methodology used to develop the new maps as part of the NH Coastal Project.

New England Coastal Fact Sheet pdf file - fact sheet highlights general information and resources related to the ongoing coastal flood hazard mapping studies in New England. The fact sheet explains the benefits and the methodologies of the studies, while providing a glossary of key terms and answering common questions asked regarding coastal flood hazard mapping studies in New England.

Mapping Data

  • 2010 1-foot orthophotography
  • 2-meter Digital Elevation Model (15 cm vertical accuracy) developed from Light Detection and Ranging (LiDAR)
  • Field data collection

Mapping Riverine Floodplains

Zone AE Enhanced Study

  • Traditional detail study
  • Sections and all hydraulic structures surveyed
  • Detailed hydrologic analysis
Zone AE
Flooding Source Miles
Exeter River 7.53
Lamprey River 4.5
Oyster River 3.75
Squamscott River 0.8

Zone A Basic Study

  • More automated approach than previously
  • Hydrology from Regional Equations
  • Hydraulic models developed
  • Floodplain boundaries mapped from model output
  • Approximately 136 miles of Zone A Basic Study

Updated Topography

Revised floodplain boundaries due to updated topography
Flooding Source Miles Flooding Source Miles
Bellamy River 2.6 Pettee Brook 1.3
Cocheco River 2.3 Pickering Brook 1.8
College Brook 1.7 Piscassic River 3.4
Exeter River 0.5 Piscataqua River 13.1
Great Bay shoreline 32.0 Squamscott River 5.0
Hamel Brook/Longmarsh Brook 1.1 Winnicut River 3.7
Little River No. 1 (Exeter) 2.3 Woodman Brook 1.2

Coastal Methods

  • Coastal Analysis
  • Field Reconnaissance

Portable Document Format Symbol Portable Document Format (.pdf). Visit for a list of free .pdf readers for a variety of operating systems.

NH Office of Strategic Initiatives
Governor Hugh J. Gallen State Office Park
Johnson Hall, 3rd Floor  |  107 Pleasant Street  |  Concord, NH 03301
(603) 271-2155  |  fax: (603) 271-2615