HomeMy WebLinkAboutAGENDA REPORT 2006 0118 CC REG ITEM 09AMOORPARK CITY COUNCIL
AGENDA REPORT
ITEM 9. A .
CITY OF MOORPARK, CALIFORNIA
City Council Meeting
A.
AC'i'Iti�iVt
BY:
TO: The Honorable City Council
FROM: Yugal K. Lall, City Engineer /Public Works Director
DATE: January 9, 2006 (Council Meeting 1- 18 -06)
SUBJECT: Consider Proposed Appeal of the New Draft Digital Flood
Insurance Rate Map [DFIRM] for the City of Moorpark and
Resolution Amending the Fiscal Year 2005/06 Budget to
Provide Funding for Certain Flood Zone Planning Efforts
BACKGROUND
New Hydrology Study and New DFIRM: For the past several years, the Ventura
County Watershed Protection District [ VCWPD] has been working with the U. S.
Army Corp of Engineers [COE], the Federal Emergency Management Agency
[FEMA] and their consultants, on a new Hydrology Study for the Calleguas Creek
Watershed and on FEMA's development of a new Digital Flood Insurance Rate Map
[DFIRM] for all of Ventura County. That effort is nearing completion.
2. New Flood Zone Boundaries: The recently completed Hydrology Study for the
Calleguas Creek Watershed yielded data which indicates that peak storm flows will
far exceed the capacity of the Arroyo Simi Channel through the City of Moorpark. As
a result, the new draft DFIRM shows many more properties within the various Flood
Zones than what is shown on the current 1986 Flood Insurance Rate Map [FIRM]. A
representation of 1986 FIRM and the draft DFIRM are attached as Exhibits 1 and 2.
3. Public Meeting: On November 9, 2005, the City Council hosted a public meeting to
discuss the draft DFIRM. Notice of that meeting was mailed to all property owners in
the City. The purpose of that meeting was to advise affected property owners of
effects of the proposed new DFIRM and of the need for owners of affected properties
to seek flood insurance.
4. Engineering Analysis: At the November 9, 2005, meeting staff advised the City
Council that the services of a consultant engineer had been retained to review and
possibly critique the data, methodologies and assumptions used by the VCWPD
PW/YI(L08002/RPT101l11 108
000001
New Draft Digital Flood Insurance Rate Map [DFIRM]
January 18, 2006
Page 2
and FEMA in determining the water surface elevations (WSE) which generated the
flood zone boundaries on the draft DFIRM.
DISCUSSION
A. Preliminary Draft Report
Attached as Exhibit 1, is a preliminary draft report from the City's consultant
summarizing the consultant's analysis of the DFIRM in support of same. That report
also sets forth the consultant's recommendations regarding possible grounds for
submitting an appeal to FEMA.
B. Summary of Consultant's Analysis
To summarize the consultant findings, there are basically five main areas of concerns
that can potentially reduce the limits of the flood plain within the city the exact limits of
the reduction up to 3 feet in water depth is yet to be determined and will be subjected
to FEMA approval of our appeal:
• Breakout Analysis upstream of the railroad bridge. In this scenario it would be
assumed that the levee upstream of the railroad bridge would fail creating a break-
out of the flow at this location. The existing channel would be capable of carrying
a flow of up to 16,000 cfs (cubic feet per second) and a break -out of 6,000 cfs
flowing through the streets and low lying areas adjacent to the channel. This
rationale was previously used by FEMA for the City of Simi Valley, wherein the
limits of the flood boundaries were reduced;
• Bridge Analysis Assumptions used by FEMA consultants including the roughness
coefficient and the modeling methodology does not compare with what was
historically used;
• The Peach Hill Wash Flood Plain was removed from the 100 year flood plain on
August 24, 1990, and this was left out of the study by the FEMA consultants;
• The Flood Plain delineation for the Walnut Canyon Drain at Casey Road does not
conform to the current topography, and detention improvements upstream of
Casey Road were not included. Revisions to the topography and inclusion of the
new detention basins may reduce the flood plain boundary in this area;
• Overflow analysis through the City is based on the over bank hydraulic
characteristics rather than the main channel analysis.
C. Consultant's Recommendation
File an appeal to FEMA for the five (5) main areas of concern based on FEMA
guidelines.
P W / V KL06002/RPT /01 /11 106
000002
New Draft Digital Flood Insurance Rate Map [DFIRM}
January 18, 2006
Page 3
D. Summary and Conclusion
Staff concurs with the recommendation of our consultant to file an appeal to FEMA
by February 28, 2006.
E. Fiscal Impact
To date City has spent approximately $15,000 towards the DFIRM review, and an
additional amount of $25,000 is needed for the preparation of the appeal. Funding
has been through the General Fund. At this time staff is requesting a budget
appropriation to cover this specific need.
STAFF RECOMMENDATION (Roll Call Vote)
1. Direct staff to retain consultant services to prepare and submit to FEMA an appeal of
the Draft DFIRM, said appeal to address the issues discussed in Section B of this
report.
2. Adopt Resolution No. 2006-
Attachments:
Exhibit 1: Consultant's Report
Exhibit 2: Resolution
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L.
KASRA /E CONSUL TING
201 BURNETT A VENUE VENTURA CA 93003
Mr. Yugal Lail, PE
Director of Public Works
City of Moorpark
799 Moorpark Avenue
Moorpark, CA 93021
Phone: 517 -6255
FAX: 529 -7358
Subject: FEMA DFIRM Review — Phase I
City of Moorpark, California
Dear Mr. Lall ( Yugal):
Exhibit 1
(805) 340 -4744
January 9, 2006
Per your request, we have completed our preliminary evaluation of the new Federal
Emergency Management Agency's (FEMA) Digital Flood Insurance Rate Maps ( DFIRM)
study for the City of the Moorpark.
The scope of this qualitative evaluation is limited due to the short time frame as dictated by
FEMA's 90 -day review process. Consequently, this letter report should not be construed as
an all inclusive and thorough evaluation of a relatively large body of information material
that has been produced by FEMA's mapping and engineering contractors for this purpose.
During the course of this evaluation, the following have been reviewed: the computer
(hydraulic) models, work maps dated September 30, 2004, the `Preliminary Flood Insurance
Study' report, and the `Flood Insurance Rate Maps (FIRM)' for `Ventura County, California
and Incorporated Areas' stamped Preliminary September 16, 2005. Additionally, some
Public Works staff were consulted on various drainage issues, who also provided
construction plans for various drainage and bridge facilities. Several field visits were
conducted to validate or evaluate hydraulic assumptions made in the computer models.
FEMA contracted with NOLTE of San Diego, California as a `Mapping Partner' to perform
the necessary engineering and floodplain mapping analysis for this project from September
2001 through September 2004. FEMA also contracted with DEWBERRY of Fairfax,
Virginia as another Mapping Partner who provided QA/QC and other services for the project.
The Preliminary DFIRM project for the City of Moorpark consists of the same three major
streams that had been mapped in detail before; Arroyo Simi, Walnut Canyon Drain, and the
Peach Hill Wash. All other floodplains remain the same as shown on the `effective' FIRM
dated September 29, 1986. No new detailed study has been performed for the other known
floodplain areas in the City.
All detailed floodplain mapping projects are based on mathematical and computer analysis
that are supposed to mimic natural processes and physical conditions on the ground.
11111•
Moorpark DFIRM Review
Page 2, January 9, 2006
The lay of the land, slope, surface and land cover, debris and sediment, rainfall and wind
condition, fire, obstruction in the drainage path, vegetation, buildings, flood channels,
bridges, levees, human activity, etc. all affect the behavior of flood waters during major flood
events. Consequently, the mathematical assumptions made to simulate the effects of the
above factors greatly influence the results of the analysis, the BFEs, and the extent of the
floodplains. Therefore, it is crucial that the basic mathematical assumptions made
correspond to accepted national guidelines.
Findings
The City's first line of defense against a catastrophic flood event is a levee system built on
the west bank of Arroyo Simi above the Railroad Bridge some thirty years ago. This levee
does not currently meet FEMA's levee requirements and it cannot be certified to provide
adequate protection against a 100 -year flood. The lower reaches of Arroyo Simi through
City of Moorpark are also hydraulically inadequate and deficient.
Generally speaking, the above study and floodplain maps have been prepared in accordance
with FEMA's guidelines and specifications. The Arroyo Simi floodplain has been delineated
conservatively and presents a `worst case' flooding scenario in the case of major levee or
bridge failure and breakouts.
Even though the contactors have followed FEMA's floodplain mapping guidelines, some of
their assumptions may have resulted in overly conservative `Base Flood Elevations' (BFE) in
parts of the City as shown on the FIRMs. A case in point is the City's Police Services Center
(PSC) which has recently been built on Spring Road approximately 4 -5 feet above the
adjacent ground. Under the new maps, the PSC would be flooded by an additional 2 -4 feet
of water during a 100 -year storm event.
The following presents the results of this preliminary evaluation and review in a few basic
categories:
Hydraulic & Hydrologic Modeling
1. The `Present Condition' hydrology information used for the hydraulic modeling effort
was provided by the Ventura County Watershed Protection District (VCWPD) in
March 2003. The total peak flows have been used properly in the models, although
the flow distribution for various sections seems to be unstable and changes rapidly
from left overbank to right overbank. This indicates hydraulic instability which may
require careful examination or remodeling. Some of the `split flows' may also
require examination and remodeling using the `inline' or `lateral structure' features in
the hydraulic model.
000005
Moorpark DFIRM Review
Page 3, January 9, 2006
2. The hydraulic model software used for this purpose is called the `River Analysis
System' developed by the Hydrologic Engineering Center of the US Army Corps of
Engineers. This software known as HEC-RAS is a standard and conventional 1-
dimensional modeling tool which is approved by FEMA, and it is used across the
United States for floodplain mapping purposes.
3. The 2001 topography with 2 -foot contour interval has been used for this purpose,
which is fairly adequate for many parts of the floodplain. However, in areas where
the depth of flow is less than 2 feet, the results may be questionable.
4. The Manning's roughness `n' factors used for the main channel and the overbank
areas are within a reasonable and acceptable range. However, the use of `vertical
variation in (n) 0.2' above the bridges such the Spring Road and the Rail Road bridge
is not a common practice and results in higher than normal water surface elevations
above bridges that are overtopped during a flood.
5. The bridge analysis seems to be somewhat conservative as they have used the
`highest energy answer' for the low flow methods, and the `energy only' for the high
flow methods. This particular assumption also yields higher than normal water
surface elevations above bridges such as the Spring Road Bridge, where the existing
bridge opening does not have enough capacity to carry the 100 -year flood. A more
typical assumption in these cases is the `momentum, pressure and weir' procedures.
6. The FIRM shows much of the Arroyo Simi flow is carried in the north overbank area
above the main channel. If that is the case, the distance between the sections and the
overall channel slope should match the overbank area, and not the main channel. It
would appear that an `overland flooding' situation is treated as a `riverine' condition.
A better approach would have been to model the overbank areas of Arroyo Simi
separately from the main channel across the entire length of the overbank.
7. The calculated `storage volume' of the overbank floodplain of Arroyo Simi is
substantially larger than the ` hydrograph volume' for the portion of the 100 -year 24-
hour hydrograph in excess of the channel capacity. This would indicate that the
overbank flooding depths and volume may be too high, as they do not conform to the
amount of overflow volume separating from the main channel. A 2- dimensional
unsteady floodplain analysis may provide a more realistic floodplain map within the
urban areas of the City.
8. The floodplain delineation for the Walnut Canyon Drain at Casey Road does not
conform to the actual topography. The latest topographic mapping may be utilized
for this purpose to determine a more accurate spill and split flow at this location and
the downstream reaches.
9. Unlike previous FEMA floodplain studies for Arroyo Simi in Moorpark, debris was
not directly taken into account in the current study by adding floating debris to bridge
piers. Debris can be a detriment to the stability of a bridge, and it directly affects the
capacity of bridges during major storm events. This is especially of concern because
of the October 2003 fire in the watershed upstream of Moorpark. The winter 2005
storm events in Happy Camp Canyon may have gotten worse as a result of the recent
fires.
Moorpark DFIRM Review
Page 4, January 9, 2006
Levee
10. The FEMA mapping guidelines for uncertified levees have not been followed
completely. Even though the analysis presented by the Mapping Partner appears to
be conservative `worst case' scenario, FEMA's `Guidelines and Specification for
Flood Hazard Mapping Partners, Appendix H: Guidance for Evaluating Flood
Protection Systems, FINAL February 2002 Section H.6' states that if the subject
levee does not meet the requirements stated in Section 65.10 of the NFIP regulations,
the 1- percent -annual-chance flood elevations will be recomputed as if the levee did
not exist. The levee built in 1976 above the Railroad Bridge does not meet FEMA's
levee requirements and therefore it falls within these guidelines.
11. The above guidelines also address the need to perform several other analyses if levees
exist on both sides of a stream, as it is the case between the New LA Avenue and the
Railroad Bridge. In these cases, `the evaluation of the levee systems shall consider
the possibility of simultaneous levee failure, failure of only the left side, and failure of
only the right side. Simultaneous levee failure shall be considered for both elevation
and regulatory floodway computations.'
Flood Insurance Study
12. The Preliminary Flood Insurance Study (FIS) Report dated September 16, 2005 is a
single document that contains the FIS reports for ALL the ten Cities and the County
of Ventura. Some portions of this document which should have been updated as part
of the current study within the Calleguas Creek Watershed have not changed, such as
the peak flow hydrology tables, and some of the Floodway tables and their
corresponding stations and water surface elevations. Other examples follow.
13. Some of the narratives about City of Moorpark are outdated and need to be corrected.
For example, on Page 30, it is stated that `the VCFCD has constructed a levee on the
west bank of Arroyo Simi between New LA Avenue and a point north of the
Southern Pacific Railroad. This levee meets the FEMA policy and, as such, is shown
providing protection against the 1- percent annual chance flood.' This statement is
incorrect as it is obvious on the new maps.
14. `Engineering Methods' narrative on Page 38 does not mention the procedures and
analysis used for the current study by the US Army Corps of Engineers (February
2003) or the VCWPD study (March 2003).
15. On Page 64, it is stated that in previous studies, `debris potential was considered in
the analysis throughout the study area.' That does not happen to be the case with the
current model, as explained above. Sediment and debris production and transport is a
natural process in this watershed, and cannot be ignored in floodplain mapping.
00000'7
Moorpark DFIRM Review
Page S, January 9, 2006
Flood Insurance Rate Maps
16. The floodplain for the Peach Hill Wash from the east limit of the current study
(approximately 900' west of Tierra Rejada) to Peach Hill Road was removed from the
100 -year floodplain on August 24, 1990, because the 100 -year flood was contained in
the underground storm drain system. The FIRM Panel is 060712 0005A (102A). A
review of the construction plans for the closed conduit portion of Peach Hill Wash
indicates that the system still has the 100 -year flow capacity based on the current
hydrology. Therefore, it is assumed that this portion of the Peach Hill Wash
floodplain should be eliminated.
Appeal Process
FEMA has placed two official notices in a local newspaper to alert community residents
about the availability of the mentioned floodplain maps (FIRM) and the FIS.
However, during a 90 -day appeal period (which began November 28, 2005), community
officials, or individual property owners working through community officials, may submit a
formal objection to the proposed BFEs to FEMA. These objections, which are referred to as
appeals, must be based on data that show the proposed BFEs to be scientifically or
technically incorrect. FEMA reviews all information submitted by the community and other
interested parties before finalizing the FIS Report and FIRM panels. If the appeal is
successful, revised preliminary maps may be issued. A protest will not result in revised
preliminary maps, but will be incorporated into the final maps if the required data is
submitted.
An appeal is a dispute of a new or revised BFE and must be based on knowledge or
information that the proposed flood elevations are scientifically or technically incorrect. A
protest is a formal objection to items on the FIRM panels other than a BFE (e.g., floodplain
boundaries or street names). The final maps are published after the compliance period ends
and all protests and appeals are resolved.
11111:
Moorpark DFIRM Review
Page 6, January 9, 2006
Conclusions
Based on the above findings, it would appear that the City of Moorpark may have a strong
enough case to appeal (and protest) the proposed floodplain maps and BFEs for the City.
However, it is difficult to know whether or not FEMA would agree with the City's reasoning
and the supporting technical and scientific data.
The following are key points on which a possible appeal may be filed with FEMA:
A. Uncertified levee above the Railroad Bridge, and the possibility of breakout flow
upstream
B. Bridge analysis assumptions (roughness, modeling approach, etc.)
C. Walnut Canyon Drain floodplain map revision at Casey Road and downstream
D. Peach Hill Wash floodplains where the map had been revised years ago
E. Overflow analysis through the City based on overbank hydraulic characteristics as
opposed to the main channel, and the `hydrograph storage' issue
Should the City decide to pursue an appeal and win the case, the resulting flood hazard areas
may be 2 -3 feet shallower in parts of the City, which may result in lower flood insurance
premiums for the affected properties. However, the actual changes to the BFEs and the
floodplain and floodway boundaries will be evident after a thorough reanalysis and approval
by FEMA.
The deadline for the 90 -day appeal period is February 28, 2006. The City and their
consultants will not have adequate time to prepare the necessary information and analysis for
an appeal by the said deadline. Therefore, a time extension request will need to be filed with
FEMA as soon as possible, should the City decide to pursue an appeal at this time.
Thank you for retaining our professional services on this important project. We look forward
to hearing from you soon. Please feel free to call if you have any questions or comments.
Very truly yours,
Hassan Kasraie, PE, CFM
Cc: Kenneth C. Gilbert
11111•
Exhibit 2
RESOLUTION NO. 2006 -
A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF
MOORPARK, CALIFORNIA, AMENDING THE FY 2005/06
BUDGET TO PROVIDE FUNDING FOR CERTAIN FLOOD
ZONE PLANNING EFFORTS FROM THE GENERAL FUND
(FUND 1000)
WHEREAS, on June 15, 2005, the City Council adopted the Budget for Fiscal
Year 2005/06; and
WHEREAS, a staff report has been presented to the City Council requesting a
budget increase in the aggregate amount of $40,000; and
WHEREAS, Exhibit "A ", attached hereto and made a part hereof, describes said
budget amendment and its resultant impacts to the budget line item(s).
NOW, THEREFORE, THE CITY COUNCIL OF THE CITY OF MOORPARK DOES
HEREBY RESOLVE AS FOLLOWS:
SECTION 1. That a budget amendment in the aggregate amount of $40,000, as
more particularly described in Exhibit "A ", is hereby approved.
SECTION 2. The City Clerk shall certify to the adoption of this resolution and
shall cause a certified resolution to be filed in the book of original resolutions.
PASSED AND ADOPTED this 18TH day of January, 2006.
Patrick Hunter, Mayor
ATTEST:
Deborah S. Traffenstedt, City Clerk
Attachment:
Exhibit 'A': Appropriation and Budget Detail
000010
Resolution No. 2006 -
Exhibit "A"
FY 2005/06
Budget Appropriations
Required for
Certain Flood Zone Panning Efforts
A. Fund Allocation
Fund No.
Fund Name
Amount
1000.5500
General Fund
$40,000
$ 40,000
$ 41,000
Total
$ 1,000
Total
$40,000
B. FY 05/06 Budget Appropriation:
BUDGET NUMBER
BUDGETED
REVISION
NEW BUDGET
1000.8100.0000.9103
$ 1,000
$ 40,000
$ 41,000
Total
$ 1,000
$ 40,000
$ 41,000
Approved as to form:
MNKL06003WT /01/1 1108 O O 0 O1 1L