Community
Community (Assoc)
USGS Gauge
IFC Bridge Sensor
IFC Rain Gauge

Major Flood Stage
Moderate Flood Stage
Flood Stage
Action Stage

Flood Risk: Above Normal
Flood Risk: Elevated
Flood Risk: Near Normal
Flood Risk: Reduced
Flood Risk: Below Normal

Flood Risk High
Flood Risk Elevated

Active Flood Map
Under Development

IFC Bridge Sensor
USGS Stream Gauge

Step 1: Hydrography Hydrography describes the geometry of Iowa's network of streams and rivers.
The Iowa Department of Natural Resources (IDNR) statewide Light Detection
and Ranging (LiDAR) dataset, which provides a very high-resolution representation
of Iowa's land surface, is used to locate stream channels and create a digital
stream network map. All channels draining greater than 24 acres are included.
Step 2: Hydrology Hydrology is used to predict the amount of water flowing in Iowa's streams.
Stream gage data and mathematical relationships from the United States
Geological Survey (USGS) are used with LiDAR and hdyrography data to
estimate stream flows.
Step 3: Hydraulics Hydraulics use physics to calculate flood depths and extents based upon
stream flow. Computer models are constructed using LiDAR and
hydrography data, and used to simulate flow behavior and estimate flood
elevations. Computer models are developed for Iowa's streams draining
greater than one square mile.
Step 4: Mapping The results of hydraulic computer models are used to create maps
showing flood depths and extents. Model results are combined
with LiDAR data and analyzed to identify floodplain boundaries.
Step 5: DFIRM Digital Flood Insurance Rate Maps (DFIRMs) are floodplain map products
used by the Federal Emergency Management Agency (FEMA) and the
National Flood Insurance Program (NFIP). Map data are formatted
according to FEMA requirements and submitted for review and adoption.