inundation, high-wave flooding, and storm surge flooding rely on integrated depth and elevation data. Such modeling exercises are often based on geospatial data that have positional uncertainties of tens of meters, in addition to the model prediction uncertainties of tens of meters. The final product, with its partially undetected errors as well as uncertainties of many tens of meters in horizontal space and several meters in vertical space, may be used by authorities for hazard management and mitigation (e.g., the identification of evacuation routes). There is enormous potential for catastrophe if vehicles are directed to use a flood-prone evacuation route that was selected because of faulty elevation data input to a storm surge model.

As discussed in Chapter 2, an additional critical information element for a wide variety of public and private entities is the shoreline position. Although depicted as a fixed line on maps and charts, shorelines are dynamic features that present unique challenges to coastal managers. The diminishing amount of land area available for development and the overwhelming importance of shorelines as economic, cultural, environmental, and recreational resources place a premium on understanding shoreline dynamics and mapping the characteristics of shoreline change.

Few state, local, or private organizations make their own maps and charts and thus must extract shoreline information from either U.S. Geological Survey (USGS) topographic maps or National Oceanic and Atmospheric Administration (NOAA) nautical charts. In a great many cases the jurisdictional needs of state and local agencies are not represented by the boundaries provided on these federal maps, and the maps themselves leave the zone between Mean Sea Level (MSL; as delineated by the USGS shoreline) and Mean High Water (MHW) or Mean Lower Low Water (MLLW; as delineated by the NOAA shoreline) unmapped because of the gap between USGS maps and NOAA charts. As a result, state and local needs are often left unfulfilled. Even worse, errors are frequently promulgated through imprecise attempts to rectify this situation. The problem of consistent shoreline definition applies equally to the Great Lakes coastline. In a funding environment where coastal zone management funds are allocated on the basis of shoreline length, equity among the states requires that a consistent set of definitions and procedures be applied.

The lack of accurate maps and charts that seamlessly cross the land-sea interface creates a serious obstacle for the coastal zone managers of our nation. These managers need precise, accurate, and timely data and products that are easily accessible and usable for a wide variety of applications. A remedy for this situation, and the committee’s vision for the future, is the development of a seamless transformation framework that is available through a single digital portal that offers data, maps and charts, and tools as well as the ability to translate rapidly from one jurisdictional



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