Who determines the boundaries of a floodplain? / What data is used to create a Flood Insurance Rate Map?.What is a 0.2 percent (500-year) flood/floodplain? / What are my chances of flooding in a 0.2 percent (500-year) floodplain?.What is a 1 percent (100-year) flood/floodplain? / What are my chances of flooding in a 1 percent (100-year) floodplain?.

What is a floodplain? / What is a floodway?.

Contact a mortgage lender or insurance agent for an official floodplain determination. As a property owner or renter, you can learn where your structure is located relative to a mapped floodplain. To learn if your structure is located in a mapped 1 percent (100-year), 0.2 percent (500-year) or coastal floodplain, visit FEMA’s online Map Service Center at There, you can view a FIRM at no charge using a property’s address. The Harris County Flood Control District encourages all residents to have flood insurance. Flooding tops the list of natural threats in Harris County. Structures near unstudied bayous and creeks could be located in an unidentified floodplain. Furthermore, of the more than 2,500 miles of bayous and creeks in Harris County, only about 1,300 miles have been studied for the purpose of identifying floodplains on the Harris County FIRM. In fact, 65 percent of the area that flooded during Allison was not in a mapped floodplain. A FIRM also does not show flooding risks from events greater than the magnitude of a 0.2 percent (500-year) flood, such as Tropical Storm Allison, which dropped unprecedented amounts of rain and far exceeded a 0.2 percent (500-year) flood in some parts of Harris County in 2001. Half or more of the flooding that occurs in Harris County falls into these two categories. A FIRM does not identify risks from street flooding caused by roadside ditches and storm sewers exceeding their capacity or from sheet flow, which is water traveling over land to reach a bayou. While a FIRM is a good indicator of flooding risks from a bayou or creek overflowing during certain floods, it does not identify all flooding risks for Harris County, which receives an average of 48 inches (4 feet) of rain each year.

Its purpose is to identify areas at risk for flooding from a bayou, creek or other waterway overflowing during 1 percent (100-year) and 0.2 percent (500-year) floods, and from coastal flooding related to storm surge from a tropical storm or hurricane. It is used to determine flood insurance rates and to assist in floodplain management and the regulation of land development. What is a Flood Insurance Rate Map and how do I use it?Ī Flood Insurance Rate Map (FIRM or floodplain map) is a map produced by the Federal Emergency Management Agency (FEMA) and adopted by a city or by a county. What is a Flood Insurance Rate Map and how do I use it? Back to Top.Floodplain Status/Floodplain Determinationįor questions pertaining to development and construction of or improvements to a property located in a floodplain, contact your local municipality or the Harris County Public Infrastructure Department’s Permit Office at (713) 956-3000 or Flood Insurance Rate Map (FIRM or floodplain map).Flood Insurance Rate Map (FIRM or floodplain map).Select one of the following to view Frequently Asked Questions and Answers related to that topic.

100 year flood maps