Revision of a traditional water and flood control plan to free land and cut costs.

The city of Sugar Land, Texas is a planned community that is growing rapidly, with the population increasing by over 30% in a decade. Sugar Land has won a series of awards for careful planning during this growth.

Arup was invited to improve a traditional 'end-of-pipe' water and flood control plan for a new 720a residential and commercial development. The site is located within a floodplain and is subject to intense rainfall that creates heavy stormwater surges.

To address both water quality and flooding, Arup developed an integrated stormwater plan.

Arup demonstrated that over 15a of land allocated for end-of-pipe detention could be freed for other use. This land could be reallocated as open space or for additional residential areas.  

The firm’s revised plan demonstrated the potential to reduce storm drain lengths and excavation requirements, reducing capital costs by nearly $1.2m.

The plan utilises low-impact development approaches to effectively manage runoff volumes, peak flow timing and water quality while improving site utilisation, reducing infrastructure costs and enhancing habitat and aesthetics.

Arup’s plan considers the costs and benefits of four water management strategies to reduce peak stormwater surges and treat waterfor sediment and urban pollutants.

Flood management areas

Rather than create a single large lake, the plan designates a number of smaller areas that will be allowed to flood during storms. Areas flooded more regularly are generally used as open space or habitat improvement while those that flood less frequently can be allocated for sports and other recreation.

Underground storage

In a planned development, numerous opportunities for underground water storage exist beneath roadways, open space and parking lots. While more expensive than floodable areas, these vaults can be designed to hold enormous volumes of water and take up almost no footprint on the surface.

Arup’s concept demonstrated that more than 15a of land previously allocated for end-of-pipe detention could be freed for other use by incorporating at-source stormwater treatment and retention devices both on streets and private parcels. This land could be reallocated as public open space or additional residential areas.

Street-level water management

Several methods were used to integrate naturalised treatment, flow control and conveyance methods into the planned streetscape. These included vegetated swales, flow-through planters, bulbouts, permeable paving, traffic calming and underground vaults.

Parcel-level best management practices

Naturalised treatment, flow control and conveyance methods were also integrated at the parcel level. These methods included raingardens, cisterns, permeable paving, planter boxes, drywells and green roofs.

The revised plan demonstrated the potential to reduce storm drain lengths and excavation requirements, reducing capital costs by nearly $1.2m.