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FEMA Simplified Method – DEM Instead of Contours?
Posted by jhframe on October 18, 2016 at 4:04 amI’ve been asked about providing an Elevation Certificate for a parcel that’s in Zone A with no BFE determined. The client wants to make improvements, and the county is requiring him to show that the improvements will be above BFE. An engineered drainage study is beyond the client’s budget. The property is in a rural area adjacent to a major creek.
FEMA allows local agencies to authorize construction — but not a flood insurance rating — based on a BFE determined by simplified methods. However, the requirement to add 1/2 contour interval to the lowest Zone A boundary elevation scaled from a quad sheet isn’t very helpful in this instance, as the contour interval is 40 feet. I’m wondering if anyone has successfully used DEM data to effectively reduce the contour interval to near zero.
Thanks!
james-vianna replied 7 years, 10 months ago 7 Members · 9 Replies -
9 Replies
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Jim Frame, post: 395673, member: 10 wrote: I’ve been asked about providing an Elevation Certificate for a parcel that’s in Zone A with no BFE determined. The client wants to make improvements, and the county is requiring him to show that the improvements will be above BFE. An engineered drainage study is beyond the client’s budget. The property is in a rural area adjacent to a major creek.
FEMA allows local agencies to authorize construction — but not a flood insurance rating — based on a BFE determined by simplified methods. However, the requirement to add 1/2 contour interval to the lowest Zone A boundary elevation scaled from a quad sheet isn’t very helpful in this instance, as the contour interval is 40 feet. I’m wondering if anyone has successfully used DEM data to effectively reduce the contour interval to near zero.
Thanks!
We’ve had little success with DEM data.
It tends to be “off” quite a bit where we’ve tried them. Maybe they are better there, it’s not difficult to check them. -
Jim Frame, post: 395673, member: 10 wrote: I’ve been asked about providing an Elevation Certificate for a parcel that’s in Zone A with no BFE determined. The client wants to make improvements, and the county is requiring him to show that the improvements will be above BFE. An engineered drainage study is beyond the client’s budget. The property is in a rural area adjacent to a major creek.
FEMA allows local agencies to authorize construction — but not a flood insurance rating — based on a BFE determined by simplified methods. However, the requirement to add 1/2 contour interval to the lowest Zone A boundary elevation scaled from a quad sheet isn’t very helpful in this instance, as the contour interval is 40 feet. I’m wondering if anyone has successfully used DEM data to effectively reduce the contour interval to near zero.
Thanks!
I can’t speak to the DEM use, but the last two certs I did that were in a A zone I just filled out the cert leaving flood depth off. Then I had my client fill out a request form and send it all in to fema. After a few months they came up with a number.
Jim -
I agree with James. Leave the BFE off and FEMA will calculate it for you.
Historic Boundaries and Conservation Efforts -
Jim Frame, post: 395673, member: 10 wrote: FEMA allows local agencies to authorize construction — but not a flood insurance rating — based on a BFE determined by simplified methods.
I was not aware of this. The elevation certificate form does not differentiate on how a given community determined BFE was developed. How does the NFIP sort this out?
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The few times I’ve used a simplified method for an EC I’ve included a report detailing how I developed the BFE, and the whole package went to the country floodplain administrator as part of the building permit application.
I don’t know what happens if someone takes one of those ECs and submitted it with an application for insurance. I guess it’s up to the underwriter to read the EC comments and catch the BFE limitation.
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James Vianna, post: 395713, member: 120 wrote: I can’t speak to the DEM use, but the last two certs I did that were in a A zone I just filled out the cert leaving flood depth off. Then I had my client fill out a request form and send it all in to fema. After a few months they came up with a number.
Jimwhere is the form you requested located on FEMA.gov?
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Jim Frame, post: 395673, member: 10 wrote: I’ve been asked about providing an Elevation Certificate for a parcel that’s in Zone A with no BFE determined. The client wants to make improvements, and the county is requiring him to show that the improvements will be above BFE. An engineered drainage study is beyond the client’s budget. The property is in a rural area adjacent to a major creek.
FEMA allows local agencies to authorize construction — but not a flood insurance rating — based on a BFE determined by simplified methods. However, the requirement to add 1/2 contour interval to the lowest Zone A boundary elevation scaled from a quad sheet isn’t very helpful in this instance, as the contour interval is 40 feet. I’m wondering if anyone has successfully used DEM data to effectively reduce the contour interval to near zero.
Thanks!
I always use the 265 Manuel and the quick2 software from fema.
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I always use the 265 Manuel and Fema’s quick 2 software.
Run two perpendicular crossections, obtain the q value and run it through the software.
It is usually pretty close to the simplified method, but we are on a 10 foot contour interval.
Db
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Joe the Surveyor, post: 395865, member: 118 wrote: where is the form you requested located on FEMA.gov?
This has worked for me twice and I just verified with a FEMA representative:
Fill out Elev. cert leaving BFE blank, have homeowner fill out section E then complete and submit a letter of map change form to FEMA. They will crunch the numbers and then arrive at a BFE.
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