Harris County Floodplain Reference Marks

Harris County Floodplain Reference Marks


In response to the flooding in June 2001 that occurred during Tropical Storm Allison, the Harris County Flood Control District (Flood Control District) and the Federal Emergency Management Agency initiated the Tropical Storm Allison Recovery Project. The project resulted in new Harris County Flood Insurance Rate Maps. The maps are used exclusively within Harris County to determine flood insurance zones and to aid in limiting future flood related damages. As a part of the project, control surveys were performed between September 2002 and April 2003 to create a large network of benchmarks known as Floodplain Reference Marks.

Click here to View our county-wide network of Floodplain Reference Marks full screen.

The Flood Control District’s system of more than 1,600 reference marks plays an important role in the permitting of development and administration of the National Flood Insurance Program in Harris County. The system aids 35 communities in Harris County with their administration of floodplain ordinances. 

Each reference mark – whether in the form of an engraved disk, rod or other type of permanent monument—is referenced to an established vertical elevation datum. Usually affixed to bridges or other stable structures, they provide a necessary reference point in determining the location of a structure in a floodplain within Harris County. 

The Harris County Floodplain Reference Marks interactive mapping tool provides information from the Flood Control District’s countywide network of reference marks. This on-line tool allows users to search by watershed, street address and other parameters to access information about specific numbered benchmarks. For each benchmark, the tool includes a description of its site location, plus a photograph and sketch of the site to help in locating the marker within the site. PDFs of the information may be easily downloaded and printed for field use.