FEMA Flood Hazard Zones

The Flood Hazard Zones are extracted from the National Flood Hazard Layer, which is a database that contains FEMA’s flood hazard map data. The database contains flood hazard information and supporting data used to develop the information. The primary flood hazard classification is indicated in the Flood Hazard Zones layer. Flood zones are geographic areas…

Watershed Boundary Dataset, 12-Digit Hydrologic Units

The 12-Digit Hydrologic Units, a component of the Watershed Boundary Dataset (WBD), depict the sixth level hydrologic subdivision of the United States. A hydrologic unit can accept surface water from upstream drainage areas and may define a drainage area with single or multiple outlet points. A 12-digit hydrologic unit, or subwatershed, supports water resource management…