UPDATED EXHIBITS FOR CHORRO CREEK LEVEE PROJECT
Chorro Creek Floodplain Resilience Assessment and Design
UPDATED EXHIBITS FOR CHORRO CREEK LEVEE PROJECT
Site 7A: Berm Setbacks and Floodplain Enhancement (City of Morro Bay Property) Site 7A includes a berm setback, new access road, and floodplain enhancement in a 3-acre area to increase habitat, increase storm flow conveyance and reduce flooding of the adjacent properties to the north and east. Site 7A would also include non-native species removal and revegetation of graded areas.
Figure 41 shows the proposed concept design of Site 7A.
Design Basis: This area is subject to frequent flooding due to several areas of berm/levee erosion resulting from aging and inadequately sized infrastructure, inadequate vegetation management, and channel migration. During the January 9, 2023, storm, this area experienced significant flooding that damaged structures and agricultural property.
Landowner Support: The majority of this work would take place on the City of Morro Bay property, and the City of Morro Bay has given initial indications that it is supportive of these proposed improvements, but this is not confirmed at this time. A small portion of the upstream-most work would take place on a privately owned residential parcel. The landowner has indicated initial support for these improvements.
Potential or Demonstrated Flood Benefits: The improvements at this site resulted in significant flood benefits to the Project Area. The hydraulic model results show that features at site 7A improve flooding in the Chorro Flats community significantly with large reduction in flood heights at 25 and 100-year recurrence interval flood events.
UPDATED EXHIBITS FOR CHORRO CREEK LEVEE PROJECT
Existing Conditions Proposed Conditions
2 Year
25 Year
100
Year
Figure 29. Chorro Creek FPRP Conceptual Design—Plan view of changes in inundation extents between existing conditions and proposed conditions during 2-,25-, and 100-year flood events, showing the effects of implementing conceptual designs at sites 7–9.
Figure 29 shows relatively drastic flood reduction and in planning zones 7, 8, and 9. The combined effects of sites 7A, 7B, 8A, 8B, 9A, and 9B decrease the incidence of overtopping of channel adjacent berms and increase conveyance capacities in San Bernardo and Chorro Creeks. Proposed conditions model results demonstrate elimination of flooding in the Chorro Creek road community and on the Morro Bay ranch property. Proposed conditions model results also show flood reductions along Quintana Road during the 25- and 100-year recurrence intervals. Cross section D cuts along Chorro Creek road and is displayed in Figure 30.
UPDATED EXHIBITS FOR CHORRO CREEK LEVEE PROJECT
Figure 30. Chorro Creek FPRP Conceptual Design—Section view of water surface elevations (feet North American Vertical Datum of 1988) for existing conditions and proposed conditions showing the effects of implementing conceptual designs along Cross Section D for the 100-year event.