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Prepared in cooperation with the Federal Emergency Management Agency, Region 1, and the Maine Floodplain Management Program, State Planning Office

Scoping of Flood Hazard Mapping Needs for Somerset County, Maine

By Robert W. Dudley and Charles W. Schalk


U.S. Geological Survey Open-File Report 2006-1100



The body of the report is available in PDF Format ( 2,027 KB)


This report was prepared by the U.S. Geological Survey (USGS) Maine Water Science Center as the deliverable for scoping of flood hazard mapping needs for Somerset County, Maine, under Federal Emergency Management Agency (FEMA) Inter-Agency Agreement Number HSFE01-05-X-0018. This section of the report explains the objective of the task and the purpose of the report.

The Federal Emergency Management Agency (FEMA) developed a plan in 1997 to modernize the FEMA flood mapping program. FEMA flood maps delineate flood hazard areas in support of the National Flood Insurance Program (NFIP). FEMA's plan outlined the steps necessary to update FEMA's flood maps for the nation to a seamless digital format and streamline FEMA's operations in raising public awareness of the importance of the maps and responding to requests to revise them. The modernization of flood maps involves conversion of existing information to digital format and integration of improved flood hazard data as needed. To determine flood mapping modernization needs, FEMA has established specific scoping activities to be done on a county-by-county basis for identifying and prioritizing requisite flood-mapping activities for map modernization. The U.S. Geological Survey (USGS), in cooperation with FEMA and the Maine State Planning Office Floodplain Management Program, began scoping work in 2005 for Somerset County. Scoping activities included assembling existing data and map needs information for communities in Somerset County (efforts were made to not duplicate those of pre-scoping completed in March 2005), documentation of data, contacts, community meetings, and prioritized mapping needs in a final scoping report (this document), and updating the Mapping Needs Update Support System (MNUSS) Database or its successor with information gathered during the scoping process.

The average age of the FEMA floodplain maps in Somerset County, Maine is 18.1 years. Most of these studies were in the late 1970's to the mid 1980s. However, in the ensuing 20-30 years, development has occurred in many of the watersheds, and the characteristics of the watersheds have changed with time. Therefore, many of the older studies may not depict current conditions nor accurately estimate risk in terms of flood heights.

The following is the scope of work as defined in the FEMA/USGS Statement of Work:

Task 1: Collect data from a variety of sources including community surveys, other Federal and State Agencies, National Flood Insurance Program (NFIP) State Coordinators, Community Assistance Visits (CAVs) and FEMA archives. Lists of mapping needs will be obtained from the MNUSS database, community surveys, and CAVs, if available. FEMA archives will be inventoried for effective FIRM panels, FIS reports, and other flood-hazard data or existing study data. Best available base map information, topographic data, flood-hazard data, and hydrologic and hydraulic data will be identified. Data from the Maine Floodplain Management Program database also will be utilized.

Task 2: Contact communities in Somerset County to notify them that FEMA and the State have selected them for a map update, and that a project scope will be developed with their input. Topics to be reviewed with the communities include (1) Purpose of the Flood Map Project (for example, the update needs that have prompted the map update); (2) The community's mapping needs; (3) The community's available mapping, hydrologic, hydraulic, and flooding information; (4) target schedule for completing the project; and (5) The community's engineering, planning, and geographic information system (GIS) capabilities.

On the basis of the collected information from Task 1 and community contacts/meetings in Task 2, the USGS will develop a Draft Project Scope for the identified mapping needs of the communities in Somerset County. The following items will be addressed in the Draft Project Scope: review of available information, determine if and how effective FIS data can be used in new project, and identify other data needed to complete the Project and its source. The Draft Project Scope will establish priority levels for flooding sources to be analyzed and mapped, and estimate schedules and associated costs for completion of the components of flood mapping.

The following subject areas are documented in this report as set forth in the statement of work: available flood-mapping-related data and documented mapping needs, community meetings and contacts, scope and prioritization of mapping needs, and project methods. Scoping-level time and costs for identified mapping needs will be provided as a document separate from this report. The appendix section of this report provides a community by community summary of information obtained and used in the scoping process for all 30 communities in Somerset County that have Flood Hazard Boundary Maps, Flood Insurance Rate Maps (FIRMs), and (or) Flood Insurance Studies


Section 1. Introduction


Scope of Work

Description of Somerset County

Section 2. Available Flood-Mapping Data and Mapping Needs

Community FISs and FIRMs

State of Maine Best Available Data (BAD) for Unnumbered A-Zones

Letters of Map Change (LOMCs)

LOMCs in Somerset County

Community Flood Ordinances

Mapping Needs Update Support System (MNUSS)

Community Assistance Visits (CAVs) and Community Assessment Contacts (CACs)

GIS Data

Base Map Data

Topographic Data

Hydrography Data

Community GIS Contact Information

Community Meetings and Contacts

Scope and Prioritization of Mapping Needs in Somerset County

Prioritized Mapping Needs and Scopes

Project Time and Costs for Identified Mapping Needs

Project Alternatives

Section 3. Options for Future Mapping and DTM Preparation

Mapping Requirements

Base Map

Digital Terrain Models (DTMs)

Flood-Insurance Risk Zones

Section 4. References Cited


Appendix A: Community Assistance Contacts and Visits: Somerset County

Appendix B: Community Contacts and Best Available Data: Somerset County

Appendix C: Community Scoping Interview Data: Somerset County

Appendix D: Existing MNUSS Data Entries: Somerset County

Appendix E: Attachments




  1. Communities and unorganized territories in (southern) Somerset County, Maine.
  2. Communities and unorganized territories in (northern) Somerset County, Maine.
  3. Hydrology of (southern) Somerset County, Maine.
  4. Hydrology of (northern) Somerset County, Maine.
  5. Orthophotography index for Somerset County, Maine.
  6. Mapping needs by community in Somerset County.Project time and costs fo identified mapping needs




  1. Organized communities and unorganized territories in Somerset County, Maine.
  2. Maine Floodplain Management Program factors and qualitative weight for prioritization of community-based flood mapping needs in Somerset County.
  3. Scoring formula for prioritization of community-based flood mapping needs in Somerset County.
  4. Prioritized community-based flood mapping needs in Somerset County requiring redelineation, limited detail study, or detail study.
  5. Prioritized community-based flood mapping need in Somerset County on the basis of nonrevised baseline-DFIRM production only.
  6. Flood Insurance Rate Map (FIRM) Horizontal Accuracy.
  7. National Standard for Spatial Data Accuracy (NSSDA)

If you have Adobe® Acrobat® or Adobe® Acrobat® Reader® installed on your computer, you may view and print the PDF version of this report. Acrobat Reader, is a free download from Adobe Systems, Inc. Users with disabilities can view information concerning accessibility at .

For further information, contact:


U.S. Geological Survey

Maine Water Science Center

196 Whitten Road

Augusta, ME 04330


(207) 622-8201


or visit our Web site at:

U.S. Department of the Interior, U.S. Geological Survey
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