Since the late 1800s, farmers in Oregon have been diking estuarine wetlands for their own agricultural benefit. Today, sea level rise is threatening to overtop and breach these dikes, as well as squeeze the remaining wetlands that exist between rising tides and dikes out of existence. Knowing the location and condition of the dikes, as well as who is responsible for maintenance, is critical for making decisions about where dikes should be breached to allow wetlands to migrate and where dikes need to be maintained to protect private and public infrastructure.
The Oregon Coastal Management Program worked with the NOAA Office for Coastal Management to create a geospatial database of dikes and levees in Oregon’s major estuaries. This inventory will be used by coastal management decision makers. Using lidar, aerial photography, and a variety of other map products, the Oregon Coastal Program created a draft data layer of these hydromodification structures and classified them into categories of levees. These draft maps were then verified through fieldwork and participatory mapping methods with local experts in each estuary system. Special districts responsible for dike maintenance were found in local government historical records, and the boundaries of these districts were also included in the maps, along with a point layer for tide gates and a polygon layer representing land influenced by levees.
Many nonprofit organizations and government agencies that conduct wetland restoration work in Oregon are using the dike inventory to prioritize future projects. The inventory is also being used to create more accurate predictions of what marshes and the coast would look like under different sea level rise scenarios. The Oregon Coastal Program and the NOAA Office for Coastal Management are working together to deliver this and other geospatial tools to coastal planners and local governments in a way that is accessible to GIS users of various experience levels.