Groundwater Flooding Risk Assessment

A large commercial and residential development in Newbury town centre required substantial subterranean works in order to provide car parking and other associated facilities.  The location of the proposed development is susceptible to flooding events given the proximity of the River Lambourn to the North and Kennet to the south. River Terrace Gravels overlie Chalk beneath the site and the area is considered particularly vulnerable to groundwater flooding given the presence of the rivers and degree of hydraulic connection with the underlying gravel and chalk aquifer.

ESI developed a steady state MODFLOW groundwater model in Groundwater Vistas in order investigate the potential for elevated groundwater levels generated by the installation of sheet piling to fully penetrate the River Terrace Deposits during construction. The baseline scenario was calibrated to observed groundwater levels and contours extracted from a regional model.

Simulated groundwater levels from the prediction scenario varied little from the baseline scenario, largely due to the highly transmissive nature of the combined chalk and gravel aquifer. The maximum increase observed upgradient of the proposed development was less than 0.03 m.  ESI’s efficiency in developing the initial prediction scenario led to the client to request further scenarios to investigate the range of dewatering rates required during construction.

Please contact ESI for more information on 'Groundwater Flooding Risk Assessment'.