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. Substantially all existing areas or areas proposed for development within the Authority are above the projected 100-year flood plain. 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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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. The Authority is working to better protect bayous from receiving excessive solids and oily substances.

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Lidar 1 foot contour maps showing elevation are now available on our website, sorted alphabetically by subdivision.