The general area of the Authority ranges in elevation from 10 feet mean sea level along the extreme eastern boundary to about 35 feet mean sea level along the northwestern boundary. In the general area of the Authority, there are three well-defined major watersheds. The three major drainage channels are Horsepen Bayou on the west, Armand Bayou in the central area, and Cow Bayou on the south and discharge through Clear Lake into Galveston Bay.

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Harris County Flood Control District provides Interactive Mapping Tools at https://www.hcfcd.org/Resources/Interactive-Mapping-Tools

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Drainage of the developed subdivisions is accomplished by means of enclosed storm sewer systems which outfall into detention ponds and/or improved channels of the three major streams.

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Lidar 1 foot contour maps from a 2017 study showing area elevations are available below, sorted alphabetically by subdivision.