floodplain mapping

Newhall Ranch Floodplain Mapping

Newhall Ranch is the largest master planned community in Los Angeles County over 13,000 acres with approximately 30,000 homes proposed.  Newhall Ranch straddles the Santa Clara River and contains over 15 tributaries.  The project contains steep foothills from the Santa Susana Mountains to existing farmland adjacent to the River.  The Ranch has a variety of constraints including rare habitat, protected species, wildlife corridors, and a variety of other physical constraints.  PACE was hired by Newhall Land and Farm to provide a biological sensitive approach to the master drainage plan.   PACE developed  an extensive multi-alternative river management plan to satisfy this approach.

PACE created over 30 different bank stabilization alignments for the main river and its major tributaries.  In conjunction with GIS and Hec-RAS, the industry standard river modeling tool developed by the Army Corps of Engineers, PACE produced over 210 floodplains.   The floodplains were generated for 7 storm events; 2 year, 5 year, 10 year, 20 year, 50 year, 100 year, and the capital storm event, per each alternative.  The results allowed PACE to provide GIS analysis on crucial items for the EIR/EIS such as scour potential, habitat loss/gain, refugia habitat potential, floodplain comparisons, velocity comparisons, restoration opportunities, and much more.