Development in Potentially Hazardous Areas

Desired Trend


Current Trend

Baseline (2006): 15.5%
Current (2011): 16.1%

Theme Prepared


Percent of development in potentially hazardous areas (500-year flood zone, potential landslide areas, and potential earthquake liquefaction areas)

Why is it Important?

Natural events such as floods, landslides, and earthquakes only become natural hazards if humans are nearby and could be affected by the event. In other words, it is the mixture of natural events and human development that creates the possibility of natural hazards. Due to population growth, more people are living in potentially hazardous areas than ever before.1 However, through land use planning and proper incentives, it is possible to direct growth away from potentially hazardous areas and reduce risk. This indicator measures the percent of development (commercial, industrial, and residential) that is located in the 500-year flood zone, potential landslide areas, and/or potential earthquake liquefaction areas. The 500-year flood zone includes areas where there is a one in 500 risk of flooding in any particular year. Potential landslide areas are those with significant slopes, which increase the risk of landslides. Potential earthquake liquefaction areas have loose and unconsolidated soils that could lose strength and liquefy in the event of an earthquake.

How are we Doing?

The percent of development in potentially hazardous areas increased from 15.5 percent in the baseline year 2006 to 16.1 percent in 2011. Development is occurring more in potentially hazardous areas than in the five county area in general (Missouri portion of the region only).2 Specifically, while the amount of development increased by 2.8 percent from 2006 to 2011 in the five county area, the amount of development in potentially hazardous areas increased by 6.3 percent,

Flood zones are the most common type of potentially hazardous area in the St. Louis region. The 500-year flood zone covers 525,000 acres in the region, while potential liquefaction areas cover 308,000 acres and potential landslide areas cover 175,000 acres. Most of the development in potentially hazardous areas is located in a potential liquefaction area (67.1 percent) and/or the 500-year flood zone (55.7 percent), while potential landslide areas are found in 22.9 percent of development in potentially hazardous areas.3

Geographic Level

Franklin, Jefferson, St. Charles and St. Louis counties and city of St. Louis in Missouri (data for additional areas within the eight county region will be added if it becomes available)


1 NASA Earth Observatory, The “Nature” of the Problem: Population and Natural Disasters; accessed on 10 January 2014 at

2Local data for the counties in Illinois is not available.

3These percentages do not add to 100 because some developments are located in areas with more than one potential hazard.

Data Sources

Federal Emergency Management Agency; Missouri Department of Natural Resources; and National Land Cover Database, Multi-Resolution Land Characteristics (MRLC)