S2 Flood Hazards

Only areas with a white background are considered part of the General Plan.

An intersection in Ontario is flooded after a storm.

Flood hazards to the  area can be classified into two general categories: flash flooding down natural channels and sheet flooding across the alluvial fans. A 100-year flood or larger event is anticipated to result in extensive property damage and temporary displacement of hundreds of households.  Catastrophic failure of any one of four retaining structures when full, has the potential to cause considerable damage in Ontario.



Minimized risk of injury, loss of life, property damage and economic and social disruption caused by flooding and inundation hazards.



Entitlement and Permitting Process.  We follow State guidelines and building code to determine when development proposals require hydrological studies prepared by a State-certified engineer to assess the impact that the new development will have on the flooding potential of existing development down-gradient.


Flood Insurance.  We will limit development in flood plains and  participate in the National Flood Insurance Program.


Facilities that Use Hazardous Materials.  We comply with state and federal law and do not permit facilities using, storing, or otherwise involved with substantial quantities of onsite hazardous materials to be located in the 100 year flood zone unless all standards of elevation, flood proofing and storage have been implemented to the satisfaction of the Building Department.


Prohibited Land Uses.  We prohibit the development of new essential and critical facilities in the 100-year floodplain.


Storm Drain System.   We maintain and improve the storm drain system to minimize flooding. (Link to Environmental Resources)


Use of Flood Control Facilities. We encourage joint use of flood control facilities as open space or other types of recreational facilities.


All Exhibits are part of the Policy Plan


All References are not part of the Policy Plan

  1. Flood Hazards Areas (Figure 5.9-2 of EIR)