12 Sep 2017

How federal policies worsen river floods

A guest post from Mike Lien (Stream Restoration Director, Friends of the Teton River, Idaho), written in response to my post on policy failure increasing Hurricane Harvey damages.

"We are working, grassroots style, to change FEMA’s view of floodplains (protection, updating maps and inappropriate mapping requirements) from little old Driggs. I was successful in updating their project Cost Benefit Analysis model* a few years ago so maybe I can do it again although this is much larger monster. In particular:
  1. FEMA’s messaging is crap. To say something is a 100-year flood event is misleading especially for an uneducated public. A 1% chance flood is much better and they are working on this, so are we. Also, modeling flood event size is also misleading. Empirical data is lacking in most watersheds so we can only use models which almost always seem to underestimate 1% flood size.
  2. FEMA floodplain mapping is a slow and onerous process that is often not even followed by local governments. It is very difficult and expensive to go through the CLOMAR-LOMAR process so most communities don’t do it and even if they try, FEMA can’t keep up. Also, it is difficult to get online and find the latest LOMA maps to even know what has changed.
  3. Dikes and levees fail catastrophically -- and when they do say hello to a 10’ [3 meter] wall of water heading for your front door. Can you say false sense of security? We started a Flood Control District on Teton Creek in Driggs with the goal of managing floods by providing and protecting floodplain a first of its kind in Idaho (taxation with representation as well!). How big of a Monroe Shock Absorber can we build? FEMA and the CORPS have their eyes on the District.
  4. As far as restoring (renovating) damaged streams, the FEMA No-Rise certification is the single largest impediment to working in urban areas. For example if a channel has been enlarged it can hold more water but probably can’t pass its sediment load due to decreased velocities meaning that it will eventually fill in and send floodwaters traversing across the floodplain. If I go to restore the channel so it can work properly again I inevitably will have to make it smaller (cross-section) but this causes a Rise in Base Flood Elevations which is a big problem for FEMA. What a mess.
So after that rant, here's my proposed solution:

If communities choose to allow development in floodplains,* then it is their responsibility to address NFIP shortcomings. To do this, communities need to follow these steps:
  1. Assess current stream channel and floodplain conditions for all waterways affected by proposed developments and
  2. Determine what if any restoration work/protection measures need to be completed prior to development to ensure the safety of their citizens. If development has already occurred then communities need to go back to step 1 and then fix any problems before allowing additional development.
[Mike's] Bottom Line: Communities need to start viewing waterway management in holistic manner and not as a series of one-off projects since inappropriate actions in one section of a waterway can affect people in upstream and downstream directions for miles. The benefits of this approach will far exceed the costs."

* My post on the Army Corps distorted Cost-Benefit methods, and how they encourage construction in flood plains.

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