fema flood insurance rate map update fema public meeting october 22, 2009
DESCRIPTION
FEMA Flood Insurance Rate Map Update FEMA Public Meeting October 22, 2009. FEMA Initiates Levee Reaccreditation Every 5 Years. Pole Crk Channel (WPD). Pole Crk Debris Basin (WPD). Heritage Levee (City). Levees Expected to be Accredited by November 2009. - PowerPoint PPT PresentationTRANSCRIPT
1
FEMA Flood Insurance Rate Map Update
FEMA Public Meeting
October 22, 2009
FEMA Initiates Levee Reaccreditation Every 5 Years
Heritage Levee (City)
Pole Crk Debris Basin (WPD)
Pole Crk C
hannel (WPD
)
Accredited:
Non Accredited:
Heritage Levee (City)
Pole Crk Debris Basin (WPD)
Non accredited levees cause Flood Zone A
Levees Expected to be Accredited by November 2009
Pole Crk C
hannel (wpd)
Accredited:
Non Accredited:
Years to Accreditation
Future Heritage Levee (City)
3 to 10
1 to 6
Pole Crk Debris Basin (WPD)
Pole Crk C
hannel (WPD
)4 to10
6 to 12
HISTORY OF SESPE CREEK LEVEE
1978: Los Serenos Flood 1979: Q-100 = 98,000 CFS 1983: COE Sespe Levee - 121,000
CFS 1979 to 2009: 6 Large Flood Flows 2006: Q-100 = 135,000 CFS
T E C H N I C A L S T U D I E S
Los Serenos 1978 Flood (pre-levee)
7
Improved Hydraulic Analysis Since 1979
1979: HEC 2 – One Dimensional Flow Analysis
2009: HEC RAS + Flow 2 D – Two Dimensional Flow Analysis
Better projection of flow from island crossover
Main Channel Shifts from West to East (1938 – 2008)
1938 1975 2005
9T E C H N I C A L S T U D I E S
Scour and Aggradation
T E C H N I C A L S T U D I E S 10
(1970s, 2004, & 2005 topography)
SC-1 Levee - Phase 3 Certification Action Plan Cost Estimate: $824,500
Raise levee 1 to 6 feet
Preliminary initial cost$6,500,000
Deepen Foundation?+3X$
A L T E R N A T I V E S A N A L Y S I S12
Preliminary Plan
Retrofit the USACE Levee
6’
1’
1’
A L T E R N A T I V E S A N A L Y S I S
Possible Modification/Replacement of Hwy 126 Bridge
Extension/replacement of exist. structure Options: 90’ extension; Raise existing
structure Cost:
$13,000,000 or
$44,000,000 Possibly
Non effective
T E C H N I C A L S T U D I E S
Summary of Key Sespe Issues Increase in estimated peak flow rates based
on additional stream gage data (+35% compared to 1979 analysis)
Shift of dominant channel from west to east fork
Active channel changes with major storm events
Lower reach of USACE levee does not meet Federal requirements
Long-term sediment deposition and local erosion
Levee foundation must be checked for adequacy for the new 100 year flow
14
T E C H N I C A L S T U D I E S
Next Steps on Sespe Creek Levee Ventura County Watershed Protection District reaches
consensus with FEMA and Army Corps of Engineers on the retrofit work necessary to restore Q-100 capacity.
Prepare Environmental Impact Report, Plans and Specifications.
Locate funds and construct improvements. Obtain Letter of Map Revision from FEMA which
removes Flood Zone “A” and requirements for flood insurance.
Accreditation: 3 to 10 years
ALL CONCEPTS AND COSTS PRESENTED TONIGHT ARE PRELIMINARY AND SUBJECT TO
SIGNIFICANT CHANGE15
Heritage Levee (City)
Heritage Levee Issues
LOMR going to FEMA this month: October 2009.
If approved by FEMA, Heritage area could be removed from Flood Zone “A” as early as Spring 2010.
Accreditation: 6 months to 6 years
Pole Crk Debris Basin (WPD)
Pole Creek Debris Basin Issues Construction of permanent
basin on hold until Heritage Bridges project moves forward.
Once approved by FEMA El Dorado should be removed from Flood Zone “A”
Accreditation: 4 to 10 years
Pole Creek Channel Issues
Pole Crk C
hannel (wpd)
VCWPD is planning to increase capacity from Q-50 to Q-100.
Schedule and funding for this work is uncertain due to issues over Steelhead Trout passage.
Accreditation: 5 to 15 years
Next FEMA map update (2012) may put some homes in east Fillmore into Flood Zone “A” until channel improvements are complete.
Accredited:
Non Accredited:
Heritage Levee (City)
Pole Crk Debris Basin (WPD)
QUESTIONS ?Pole C
rk Channel (w
pd)
Largest Sespe Creek Floods Prior to 1979
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
1933
1936
1939
1942
1945
1948
1951
1954
1957
1960
1963
1966
1969
1972
1975
1978
1981
1984
1987
1990
1993
1996
1999
2002
2005
2008
FLO
W C
FS
1938 = 56,000 CFS
1969 = 60,000 CFS
1978 = 73,000 CFS
2005 = 85,300 CFS
Q-100 Hydrology
Analysis, 1979Q-100 Hydrology
Analysis, 2006
New 100-YR Flow
Old 100-YR Flow 98,000 CFS
10 Largest Sespe Creek Floods
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
1933
1936
1939
1942
1945
1948
1951
1954
1957
1960
1963
1966
1969
1972
1975
1978
1981
1984
1987
1990
1993
1996
1999
2002
2005
2008
FLO
W C
FS
1938 = 56,000 CFS
1969 = 60,000 CFS
1978 = 73,000 CFS
2005 = 85,300 CFS
Q-100 Hydrology
Analysis, 1979Q-100 Hydrology
Analysis, 2006
New 100-YR Flow 135,800 CFS
New 50-YR Flow 102,000 CFS
