[env-trinity] Trinity Journal: FEMA rolls out new Trinity River maps

[Tom Stokely]

This is a June 2013 article that I think I missed, but is still relevant.
TS
http://www.trinityjournal.com/news/environment/article_746125be-d87f-11e2-a595-0019bb30f31a.html 

FEMA rolls out new Trinity River maps
Sally Morris The Trinity Journal | Posted: Wednesday, June 19, 2013 6:15 am
    New Trinity River floodplain maps are in the process of being adopted by the Federal Emergency Management Agency, having the potential to affect insurance rates and construction permits for numerous private property owners along the river from Lewiston down.
    Public workshops were conducted last week in Douglas City and Junction City and with the Trinity County Board of Supervisors to share the proposed FEMA maps that are based on recent studies conducted by the California Department of Water Resources based in Red Bluff.
    Trinity County Director of Transportation and Planning Rick Tippett said that updating the federal maps is a FEMA project, and the county’s only role is to help present the new information to the public.
    The new maps will ultimately replace the existing floodplain maps created in 1976 using the flow calculations and engineering methods available at that time to survey the river corridor every 2,000 feet.
    Noting that huge advancements in technology have occurred since then, Tippett said the ability now exists to survey large areas and produce much more accurate, high resolution pictures and data.
    “FEMA is not adding or taking anyone out of the floodplain. They are updating the maps with today’s technology, now looking at segments every couple hundred feet so the accuracy is much greater than before,” he said.
    Some property owners are finding out they are in the floodplain where the old studies indicated they weren’t. Tippett said it is still possible to obtain a building permit for existing parcels in the floodplain, but they can’t be subdivided.
    Once adopted, the maps will result in changes to flood risk classification for many property owners and show some properties in the Special Flood Hazard Area that are not included now, resulting in insurance premium changes for some residents. Any new flood zone residents will be required to purchase flood insurance if they have a federally backed home loan.
       An exact number of affected parcels was not available, but impacted areas include Coopers Bar, Junction City, Steiner Flat, Douglas City/Indian Creek, Poker Bar, Steel Bridge Road, Bucktail and Salt Flat.
    The draft maps depict where the river will rise in the event of a 100-year storm event and a 500-year event. There is a one percent chance of a hundred-year flood in any given year.
    Contracted by FEMA to perform the newest studies in 2009, DWR project manager Todd Hillaire emphasized that the draft maps are based on local conditions of topography and hydrology.
      He said studying the area from Lewiston to the North Fork Trinity River confluence included an exhaustive review of all rainfall and gauging data in the river, calculations of tributary runoff, reservoir operation data for Lewiston Dam releases and Trinity River Record of Decision flow releases.
      “We take the worst case of all those flows occurring during that given 100-year event, coupled with topography, and we develop a hydraulic model that we use to generate new water surface elevations for 40 river miles,” he said.
    In some areas, the new maps follow the old ones pretty closely, but in many cases the picture of potential inundation is very different, Hillaire said, adding “we believe this is the best representation we can give you of the river.”
    FEMA regional engineer for Region 9 Kathleen Schaeffer, from Oakland, presented some history on the National Flood Insurance Program, created in 1965 to make insurance available to all while charging people in high risk flood zones more for insurance than those in low risk areas.
      Over time the program has been revised and stiffer penalties added for non-compliance in the wake of devastating hurricanes and floods that placed the federal government on the hook for billions of dollars in damage to cover homeowners who lacked insurance and walked away from their mortgages.
    Stiffer mapping requirements have also evolved to provide local communities with better information on which to base planning and building decisions. The 2009 study of the Trinity River was prompted by a need to convert old paper maps into digital format.
    Schaeffer said the hydraulic model and resulting draft maps have been subject to rigorous, independent quality assurance review. The draft maps available for public review now will be rolled out in the fall as official preliminary maps that will be subject to a 90-day review and appeal period, followed by a six-month period before a final determination is made.
    She said her concern about the Trinity study is the high velocities predicted in a flood, creating more of a threat to life and public safety issue.
      “It will be like several thousand Ford F150 trucks coming past people’s homes. We often get dialogue about insurance, but my hope here is that you will also be engaging emergency service providers because of these high velocities coming by people’s homes,” she said.    
     Several comments were offered by homeowners in some of the affected areas.
    Jim Smith of Douglas City argued that the only mapping changes appear to be where the homes are.
    “The old line might have come to the edge of houses, and now it goes right through them,” he said, challenging some of the data as potentially biased, especially any provided by the Trinity River Restoration Program. He requested that at least a manual survey be conducted where the margins are within just a few feet in or outside of the floodplain.
    Others questioned how restoration program activities in the river such as injecting gravel and transporting it with high flows may have altered the riverbed and raised the base flood elevation.
    Clark Tuthill said his home at Poker Bar was 100 feet out of the floodplain when he bought it “and now it’s right at the edge. There’s been so much done to the river with manmade mitigation changing the river bottom. We can see where fishing holes have filled in. It seems there should be some sort of stopgap for awhile to let nature take its course.”
    Sup. Debra Chapman noted that a naturally flowing river “is very dynamic. It moves around a lot, every year.” She added it is always surprising to see where some homes have been built in areas she remembers seeing underwater as a child growing up here.
    “I’d rather see it go back to a natural river than a bunch of bulldozers and the flows set up in the ROD (Record of Decision),” Tuthill said.
    Paul Catanese of Poker Bar also objected to the gravel injections upstream he blamed for raising the floodplain.
    “We have fought that every year, but our river guides’ association has been run over by the federal government. We built here in 1988 based on the floodplain maps then and a lot of things have changed. This will cost Trinity County millions and millions of dollars in property value,” he said, urging a break in restoration program activities “because every drop of gravel being put in is raising that floodplain.”
    The draft work maps can be found at three locations: a FEMA Web site, www.r9map.org, a FEMA link on the county Web site at www.trinitycounty.org, or by visiting the Trinity County Department of Transportation office in Weaverville. Formal Preliminary Flood Insurance Rate Maps are anticipated to come out in October for public review and comment.
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