Coastal Services Center

A Roadmap to a Seamless Topobathy Surface

Bringing together the resources to simplify coastal digital elevation models

A topobathy digital elevation model (DEM) is a single surface that combines the land elevation with the seafloor surface and which can be used to examine processes that occur across the coastal and nearshore areas. Using a high-accuracy seamless topobathy DEM is essential to understanding where water will move when modeling processes such as sea level rise, hurricane flooding, tsunami inundation, and riverine flooding. This series of products will help users create seamless coastal maps, a task that has been highlighted as an important national need by the National Research Council.

Topobathy DEM of Charleston, SC created from 2007 NOAA CSC lidar data and NOS hydrography data. Click to enlarge.

A Roadmap to a Seamless Topobathy Surface (Roadmap) is a series of documents and maps that seeks to improve and streamline the process of creating a seamless topobathy DEM. It aims to make topographic and bathymetric data and reference information accessible and make connections between data set quality and DEM application (such as coastal inundation modeling). Understanding the links between input data quality and application can help create a DEM surface designed for a particular use, help data collectors provide data sets that meet needs, and help technical users define their data needs more explicitly. Roadmap may also be useful to managers who are involved in activities such as planning a data collection. Roadmap examines resources and processes associated with DEM creation, including the following:

1. Available data resources
2. Processes to generate high-resolution DEMs that minimize error
3. Examples of topobathy applications

Data Inventory: Gulf of Mexico

The first part of the Roadmap series is an inventory of available topographic and bathymetric data resources. The first inventory investigates data resources in the Gulf of Mexico, "Topographic and Bathymetric Data Inventory: Gulf of Mexico (Gulf Inventory)". The Gulf Inventory increases awareness and use of existing topographic and bathymetric data sets, decreases duplication of effort, and strategically targets data collections to fill gaps. It is a "snapshot" of data availability as of November 15, 2007, and it identifies location, collection date, and sources of available data sets. The Gulf of Mexico coastal area was chosen for this project to assist data coordination efforts and enhance geospatial capacity across the Gulf states. The next "Topographic and Bathymetric Data Inventory" will be for the Southeast portion of the U.S. from Florida to Maryland.

View Data Inventory Maps

Topographic and Bathymetric Data Considerations

"Topographic and Bathymetric Data Considerations: Datums, Datum Conversion Techniques, and Data Integration (Data Considerations)" is the second part of the Roadmap. It is important for a surface to have data inputs that are positioned in reference to the same metric if it is used to accurately portray the nearshore and coastal areas. The consequences of having mismatched datum reference can show up in the DEM grid as a sharp drop-off in the data or as a wall; either of these will have a large impact on how water flows across the land-water interface. This document strives to improve and streamline the process of creating DEMs by providing a review of available datum conversion and integration techniques. It describes the importance of establishing a uniform reference for multiple data sets and techniques for manipulating and joining data sets.

Topobathy Applications

The third part of the Roadmap will highlight some common coastal applications that can benefit from a highly accurate, high-resolution DEM. This reference, which is not yet completed, will describe applications of topographic, bathymetric, and topobathy DEMs and address standards for input data and the resulting DEM for an application. This information will help guide users on the practical and potential needs and uses of coastal elevation data and also provide technical users of elevation data with information to create a DEM specific to the needs of their application. Some examples of applications that may be addressed are shoreline delineation, wetland mapping, and inundation modeling. This document is currently in development and will be available online.

For more information please contact the NOAA Coastal Services Center