Скачать презентацию Tillamook County OR Flood Study Board of Commissioners Скачать презентацию Tillamook County OR Flood Study Board of Commissioners

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Tillamook County, OR Flood Study Board of Commissioners’ meeting June 23, 2010 Tillamook County, OR Flood Study Board of Commissioners’ meeting June 23, 2010

Agenda • National Flood Insurance Program (NFIP) • Map Modernization Program • Tillamook County 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 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, 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 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 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 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 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 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 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 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. 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 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 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 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 Hydrologic Assessment Location Gage 14301500 Wilson River near Tillamook, OR through 2008 Drainage Area (square miles) 2008 FFA Computed Discharge (cfs) Frequency Confidence Limits 2002 FIS Discharge (cfs) 25 percent 75 percent 10 -Year 28, 500 29, 700 27, 400 25, 000 50 -Year 161. 0 Discharge 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 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 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 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 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. 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 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 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’ 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 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 Apply local parcel and topo layers…

Digital Flood Insurance Rate Maps Zone Designation Changes Old FIRMs New FIRMs Definition A Digital Flood Insurance Rate Maps Zone Designation Changes Old FIRMs New FIRMs Definition A A Approximate Floodplain (SFHA) A 1 - A 30 AE Detail River Floodplain (SFHA) A 99 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 V 1 -30 VE Detailed Coastal Floodplain

Digital Flood Insurance Rate Maps FIRM Labels • AE Zone • X Zone (shaded) Digital Flood Insurance Rate Maps FIRM Labels • AE Zone • X Zone (shaded) • Floodway

Digital Flood Insurance Rate Maps Some new labels on d. FIRMs look like this… Digital Flood Insurance Rate Maps Some new labels on d. FIRMs look like this… X (Un-shaded ) X (Shaded) (500 -year) Floodway A & AE Zones SFHA (100 -year)

Tillamook County Adoption Process Tillamook County Adoption Process

Post Pre. Liminary Processing Timeline of events • Preliminary maps issued ………. . December Post Pre. Liminary 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 2 nd 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. 6 A – The sole basis of appeal under this Appeals 44 CFR 67. 6 A – 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 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: RSC [email protected] com Questions: Phone: 206 -682 -1159 ext. 2225

Comments • #1– Floodway crosses across school despite the entire area uniformly being raised 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 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 - 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 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) 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