LAN is currently developing a City-wide master drainage plan covering more than 64 square miles of contributing drainage area on Galveston Island, including 63 miles of storm sewer and 22 miles of cross culverts.

The study works to evaluate the existing system and form the basis of proposed flood risk reduction concepts across several problem areas around the City. CIP integration, a funding framework, and an operations & maintenance manual are also included as part of this project.

The Stormwater Master Plan plan includes the evaluation of the existing drainage system under various influence conditions that are unique to coastal environments, such as high/low-tide and future sea-level rise.

LAN will update the City’s existing GIS database to integrate it with the InfoWorks ICM 1D/2D model, enabling future improvements to be evaluated seamlessly in tandem with the overall City-wide modeling effort. LAN plans to divide the City into a minimum of two primary
drainage areas: the East End and the West End. Since the East End is primarily storm sewer infrastructure and the West End is primarily roadside ditch and culverts, the improvement concepts will vary and can be evaluated separately.

Multiple interconnected storm sewer trunklines extend through the City, these individual systems often interact via surface overland flow when they reach capacity and overflow onto the surface. Due to the flat topography of the City, overland sheet flow has the potential to cascade across multiple different systems before reaching a final storm sewer outfall. Understanding the interactions of subsurface and overland flow will prove critical to identifying solutions to the problem areas.