Groundwater flow model of a coastal aquifer, Malibu, California

A groundwater model was developed for a 14-acre site in Trancas Canyon, along the Malibu coast, Southern California. A GIS was used in conjunction with the Visual MODFLOW(c) groundwater modeling package to determine effects on groundwater levels at Broad Beach due to wastewater disposal from proposed development on the terrace north of the beach.; Constant-head boundary conditions were set north of the site to simulate recharge from existing homes and along the high tide line to simulate the ocean. Observed groundwater elevations and estimated recharge rates, 25,240 L/d, from surrounding sites were used to calibrate the model in a steady-state mode. Injection points were added to simulate recharge from site development. Results show that a 1.7 cm rise in groundwater elevation will be experienced at Broad Beach. This amount will not adversely impact the site and will likely be masked by the tidal influence of 10 cm.