Tillamook County, OR
Flood Study
Board of Commissioners’ meeting
June 23, 2010
Agenda
•National Flood Insurance Program (NFIP)
•Map Modernization Program
•Tillamook County Flood Insurance Study
(FIS) Review
•Map Adoption Process
Purpose of the NFIP
Reduce economic loss caused by flood events
• Maps the flood risk and assign insurance rates
(FIRMs)
• Makes flood insurance available
• Sets minimum floodplain construction
standards
• Reduces dependency on structural flood
control
• Promotes floodplain management practices
NFIP Facts
Nationally...
•5.6 million flood
insurance policies
•20,532 participating
communities
•$1.2 trillion in flood
coverage
How the NFIP Works
Three disciplines of the
NFIP:
•Mapping – Flood
Studies
•Regulations
•Insurance
Flood Studies
• FIS creates maps that show Special Flood Hazard Areas
(SFHA); base (100-yr) floodplain
• FIS sets flood insurance rates per the maps
• Lenders must require flood insurance in the 100-year
floodplain for Federal-related loans
• FIS provides communities with data to enforce their
ordinances
• Study Report: Describes flood history, principal flood
problems, flood protection measures, hydrology and hydraulic
methods, floodway data tables, water surface profiles
• Flood Insurance Rate Map (FIRM): Shows floodplain limits,
base flood elevations (BFEs), floodways, surveyed cross
sections, corporate limits, roads, insurance zones
Flood Insurance Rate Maps (FIRM)
Who uses the FIRM?
• Local Jurisdictions
- Community Officials
- Building and Zoning Departments
- Economic Development
- Planners
- Emergency Managers
• Lending Institutions
• Surveyors & Engineers
• Builders/Developers
• Insurance Agents
• Property Owners
• State and Federal Agencies
When Will it Flood?
Flood Frequency
Years
Chance in any Year
% chance over
30 yr mortgage
10
10 out of 100
96%
50
2 out of 100
46%
100
1 out of 100
26%
500
.2 out of 100
6%
Base Flood
•A flood that has a 1% chance of being
equaled or exceeded in any given year.
•Base Flood Elevation (BFE) - the elevation
that the base flood is expected to reach.
Base Flood = 100-year flood
What is Map Modernization?
Through Map
Modernization…
…FEMA will provide
digital flood insurance
rate maps and studies…
…for communities
nationwide…
…that are more accurate,
easier to use, and more
readily available.
Why Modernize?
2005
•
•
•
•
•
2007
2009
Outdated maps (10+ years old)
Physical changes in floodplains – man-made and natural
Digital format enables overlays/analysis
Easier to update maps
Maps are foundation for flood risk reduction and
insurance (5.6 million policies, 1.2 trillion coverage)
Tillamook County
Flood Study Details
Contractors: WEST
Consultants, Inc., &
Michael Baker Jr., Inc.
FEMA Funds: $520,000
Tillamook County Preliminary FIS:
December 31, 2009
History
Pre-Scoping Report – January 2006
Establish Community Contacts, Retrieve Data (models, LOMRs, needs),
Level of Study, Available Base Map Data
Scoping Meeting – March 11, 2006
Discuss proposed scope of work, identify available data and update needs,
14 Attendees (FEMA, County, Cities of Tillamook and Garibaldi, State,
USACE, WEST)
Large Flood Event – November 6, 2006 –
Wilson River near Tillamook - 38,600 cfs vs FIS 100-year – 36,300 cfs
Large Flood Event – December 3, 2007–
Wilson River near Tillamook – 33,100 cfs
Scope of Work
•Re-assess hydrology
•If not within tolerance, evaluate effects on the BFE
•Re-delineate floodplain extents along reaches where
we obtained newer topography and aerial photos
•Refine floodplain boundaries
•Digitally convert effective FIRMS
– All effective panels, except for detailed re-study of Miami,
Kilchis, Wilson, Trask and Tillamook Rivers
Hydrologic Assessment
•Wilson/Trask/Tillamook hydrology modified
because of large floods in 2007 and 2008
•Kilchis hydrology unchanged (within 2% of
effective)
•Miami 100-year hydrology increased from
6,600 cfs to 9,550 cfs based on flood
frequency analysis
Hydrologic Assessment
Location
Gage
14301500
Wilson
River near
Tillamook,
OR
through
2008
Drainage
Area
(square
miles)
161.0
2008 FFA Computed Discharge (cfs)
Frequency
Confidence Limits
2002 FIS
Discharge
(cfs)
Discharge
25percent
75percent
10-Year
28,500
29,700
27,400
25,000
50-Year
37,600
39,700
35,800
33,000
100-Year
41,400
43,900
39,300
36,300
500-Year
50,200
53,800
47,200
43,500
Trask River 100-year Flow went
from 27,400 to 33,500 CFS
Floodway
•Area where water velocities and depths are
the most destructive
•Defined as the channel of a river or other
watercourse and the adjacent land areas that
must be reserved in order to discharge the
base flood without cumulatively increasing
the water surface elevation more than a
designated height (1 foot).
FLOODWAY SCHEMATIC
100 YEAR FLOODPLAIN
FLOODWAY
SURCHARGE
FLOODWAY + FLOODWAY FRINGE = 100 YEAR FLOODPLAIN
SURCHARGE NOT TO EXCEED 1.0 FEET
Hydraulic Model
•Based on Corps flood reduction model (2004)
– Cross sections from a variety of sources (County,
previous FEMA, and Corps surveys)
– Sections extended the overbanks using 2-ft topo
from late 1999
– Calibrated to events in Nov. 1999, May 2001 and
Nov. 2001
•Some modifications to:
– Expand the sections to contain the 0.2% flood
– Fix split flow in SW part of model
Floodway Development
•Lower Trask River and Tillamook River did
not have defined floodways
•Wilson River floodway needed updating to
new hydrology and hydraulics
•Initially “adopted” effective floodways
– Worked for upper Wilson and Trask, but not
downstream
•Floodplain and floodway mapped to 2-ft
contours
DFIRM Conversion Reaches
Detailed Study – Approximately 80 miles
Distance (mi)
Nehalem Bay
4.0
Nestucca Bay
3.7
Nehalem River
15.1
NF Nehalem River
5.2
Nestucca River
16.0
Three Rivers
4.9
Wilson River
4.3
Pacific Ocean
28.4
DFIRM Conversion of 28 FIRM and 7 FBFM Panels
What’s new
Flood Insurance Study
•New maps are county-wide
•Follows a USGS Quad layout – countywide coverage
with no city “cut-outs”
•Contains 100- & 500-year floodplains (AE/X zones)
•10, 50, 100, 500 year flood elevations published
•Re-delineation of flooding sources where better
topography was available
•Vertical Datum change (NGVD 1929 to NAVD 1988)
What’s new
Vertical Datum Change
• NGVD 29
– Based on a mean sea level from 21 tidal stations in
the US & 5 stations in Canada
• NAVD 88
– Based on the density of the Earth instead of varying
values of sea heights
– More accurate
• Conversion for Tillamook County Varies
– NGVD + (vertical adjustment’) = NAVD
– Conversion factor for County for FIS is 3.54 feet
Digital Flood Insurance Rate Maps
Vertical Datum and FIRMs (e.g. uses 3.54’ conversion)
NGVD 29
NAVD 88
15
15
10
10
5
BFE = 2 ft
BFE = 5.54 ft
5
0
0
Digital Flood Insurance Rate Maps
Digital Format
Special Flood Hazard Areas
Land Ownership
Transportation
Surface Waters
Boundaries
Geodetic Control
Elevation
Aerial Imagery
Digital Flood Insurance Rate Maps
Apply local parcel and topo layers…
Digital Flood Insurance Rate Maps
Zone Designation Changes
Old FIRMs
New FIRMs
Definition
A
A
Approximate Floodplain (SFHA)
A1- A30
AE
Detail River Floodplain (SFHA)
A99
A99
Protected by Levee
AH
AH
Shallow Floodplain with BFE
AO
AO
Shallow FP without BFE
B
X (shaded)
500 Year Floodplain
C
X (un-shaded)
Outside 500 Year Floodplain
D
D
Undetermined Floodplain
V
V
Approx Coastal Floodplain
V1-30
VE
Detailed Coastal Floodplain
Digital Flood Insurance Rate Maps
FIRM Labels
•AE Zone
•X Zone
(shaded)
•Floodway
Digital Flood Insurance Rate Maps
Some new labels on dFIRMs look like this…
X (Un-shaded )
X (Shaded)
(500-year)
Floodway
A & AE Zones
SFHA (100-year)
Tillamook County
Adoption Process
Post PreLiminary Processing
Timeline of events
• Preliminary maps issued ………......... December 31, 2009
• Hold Coordination Meeting ……........ March 31, 2010
• Public Meeting……………………................................. May 12, 2010
• 90 day appeal period begins ……... e.g. June 15, 2010
after 2nd public notice in local newspaper
• 90-day appeal period ends……......... e.g. September 15, 2010
FEMA reviews submitted technical appeals and
modifies or maintains maps as appropriate
• FEMA issues “Letter of Final
Determination (LFD)” ………………………... Est. December, 2010
to communities and publishes the BFEs in the
Federal Register
Communities have 6 months to adopt the study
before the data becomes “effective”. Failure
to adopt results in suspension from NFIP
• Effective date ……………………………............ Est. June, 2011
Appeals
44 CFR 67.6A –
The sole basis of appeal under this part shall be the possession
of knowledge or information indicating that the elevations
proposed by FEMA are scientifically
or technically
incorrect.
Because scientific and technical correctness is
often a matter of degree rather than absolute (except where
mathematical or measurement error or changed physical
conditions can be demonstrated), appellants are required to
demonstrate that alternative
methods or
applications result in more correct
estimates of base flood elevations, thus demonstrating
that FEMA's estimates are incorrect.
Appeals
Signed Letter with Backup Technical Information
Mail to:
STARR - Region X Support Center
901 Fifth Avenue, Suite 3100
Seattle, WA 98164
Informal Comments not needing a response:
Email: RSC10@STARR-team.com
Questions:
Phone: 206-682-1159 ext. 2225
Comments
•#1– Floodway crosses across school despite the entire area
uniformly being raised 10 feet above river bank. Can the
floodway be adjusted to not include school since it looks like
it would either convey over the entire area or not at all?
Backup Documentation – Zoomed in map of area, address
topography
•#2 – Area has flooded numerous times in the past. Why is it
mapped as dry?
Backup Documentation – Zoomed in map of area, address,
photos, topography
Comments Not Able to Address
#1 - My house has never flooded in xx number of years, why
am I being shown wet?
Problem – The 100-year flood is generally larger than recent
floods. We need technical information that shows the
calculations are incorrect (flow, stage, topography)
#2 - There is newer topography since you started the study.
Please redo study to newer topography.
Problem – Too expensive and time-consuming and would
never be able to complete a study. Not a valid appeal by
definition.
Letters of Map Change (LOMC)
(ways to appeal at any time)
•LOMA - for property owners who believe a
property was incorrectly included in a SFHA. An
elevation certificate supports a LOMA, but by itself,
does not remove the insurance requirement.
•LOMR – removes land that has been graded or
filled (physical changes) since the date of the map.
A LOMR can waive flood insurance requirements.
• (LOMA) Hotline - 1-877-FEMA-MAP
Future Steps after
Appeal period ends
• FEMA addresses submitted
comments
• Local jurisdictions adopt an
ordinance that is compliant with
your map and FEMA standards
• Local jurisdictions develop and
implement outreach strategies, if
desired.
• Upon receipt of LFD, local
jurisdictions begin enforcing the
maps
Letter of Final Determination (LFD)
•Starts with the Letter of Final Determination (LFD)
stating that the Appeals have been resolved, if applicable
•Officially notifies community of final base flood
elevations
•Indicates effective date of FIRMs as 6 months from the
date of the letter
•Ordinance meeting FEMA regulations MUST become
effective by end of 6 months or community will be
suspended