Environmental Impact Statement - Sonoma Land Trust

California Department of Fish and Game
U.S. Fish and Wildlife Service
Section 3.2. Surface-Water Hydrology,
Tidal Hydraulics, and Sedimentation
• Construction of a tidal connector channel through the existing salt marsh and
mudflats to San Pablo Bay;
• Sediment deposition within the restored wetlands.
Thresholds of Significance
Criteria used for determining the significance of an impact on surface hydrology
are based on the State CEQA Guidelines and professional standards and
practices. Impacts were considered significant if an alternative would:
• substantially alter drainage patterns, flow rates, or volumes;
• increase the risk of flood peaks or volumes that would damage infrastructure
or property or endanger public safety;
• place within a 100-year flood hazard area structures that would impede or
redirect flood flows;
• expose people or structures to a significant risk of loss, injury, or death
involving flooding, including flooding as a result of the failure of a levee or
dam;
• result in hydrologic changes that could adversely affect existing or planned
biological communities;
• result in the need for new drainage facilities and capital expenditures; or
• increase the potential for erosion or sediment deposition.
Regarding tidal hydraulics, impacts were considered significant if an alternative
would:
• alter the magnitude and direction of tidal circulation outside the immediate
zone of subtidal and outboard marsh channels constructed for the project;
• alter the large-scale morphology of mudflats and subtidal channels outside
the immediate zone of the project;
• cause erosion of the perimeter levee, thus increasing the risk of tidal flooding
on adjacent properties; or
• induce or aggravate erosion of the existing outboard salt marsh.
In addition to these criteria, the consistency of the Project and existing flood
zoning designations were considered when evaluating the significance of
potential project effects.
Sears Point Wetland and Watershed Restoration
Project Final Environmental Impact
Report/Environmental Impact Statement
3.2-11
April 2012