LOMR - Duplicate Effective 1

[Rye1]

Froude - I hope you chime in.

I'm working on a LOMR - FEMA region IV. The FIS records all the profiles for all of the events, the channel invert is shown in the profiles, the WSEs are shown for the various events, but there isn't an effective model available. Apparently, the model that was used to create the FIS has been lost to the ages. Now, jump forward, there is a subdivision plan submitted and they have a CLOMR from FEMA approved prior to the end of construction in 2009. I'm trying to complete the LOMR following the CLOMR to perhaps restart the project. The reviewer is requiring me to create a duplicate effective model that matches the existing older FIS model. No one knows exactly what was in the field when the original model (now lost) was created. Is there an NFIP rule or reg that states that the Duplicate Effective model matches with +/- so many feet of the exiting model?

Robert Billings

http://www.newrivereng.com

 

[beej67]

Sounds prohibitively difficult to me. I'm interested to hear responses from folks who do these routinely.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[froude]

Rye1,

Unfortunately, I've run into this situation a few times. In one instance, I was able to prove to the local reviewer and the FEMA reviewer that the FEMA library was unable to provide an effective model (I did this by documenting correspondence with the FEMA library in which the library specialist specifically told me they did not have the model). In lieu of this, they accepted the new model I created, which began downstream at a Known WSEL from the FIS profile.

There is a statement on page 10 of the MT-2 instruction forms (Link) that says "If the effective model is not available, the new model must be calibrated to reproduce the FIS profiles within 0.5 foot." Hopefully if there are any old work maps, dFIRM data, or the effective FIRM, at the very least, you can create some semblance of a "duplicate" model. It may be that the current stream hydraulic conditions will give you results that are within this threshold. If they don't, I would try to convince the reviewer that it's nearly impossible to recreate old hydraulic conditions without knowing anything.

I don't know which US Army Corps region you are in, but in my region, the Corps is frequently able to produce hydraulic models which FEMA claims to not have. These models are often the effective model (or very close to them; close enough, anyway).

It seems that every time FEMA changes the consultant it uses for its library, more and more data is lost. Hope this helps. Good luck!

 

[Rye1]

I've created a duplicate effective model but I had to truncate the model to only include the immediate project area. There is an existing road crossing down stream of the project site that has been revised since the FIS profiles. I briefly tried to reproduce the profile through the crossing but found that without some kind of information about what was there in the past, it was virtually impossible.


Robert Billings

http://www.newrivereng.com

 

[gopher669]

That seems to be a standard comment on their first review letter. Make sure to talk to your reviewer, they may waive the requirement. I've gotten out of creating the duplicate (and/or corrected) effective model after explaining to the reviewer that I don't have accurate topo from 10-20 years ago, and that anything I put together would just be a complete fabrication.