FEMA for Land Surveyors is a support group for land surveyors regarding the common services directly involving FEMA that land surveyors provide for clients. These include LOMA, CLOMA, LOMR-F, CLOMR-F, etc
Greetings.
I'll start this by saying I am not posting this as a surveyor, but as a homeowner who happens to understand a thing or two about surveying. I am occasionally "just a surveyor" as my job requires it...but that's another story.
My question/dilemma pertains to the LOMA process and how the BFE is determined for the EC.
The property in question is shown in the 100-year FP on a FIRM. I have also tracked down the FIS with accompanying profiles and Floodway Data Tables. I have interpolated a BFE from the FIRM, plotted out a BFE on the profile and found the closest regulatory water surface elevation (aka: BFE) from the Flootway Data Table. Each being a little different with the FIRM highest BFE and the data tables the lowest.
I have called several surveying companies around town that claim to be experts in the LOMA process and have been getting widely varying opinions on how they will determine BFE, including one extremely bizarre conversation where an individual became irate and started screaming at me telling me I was crazy if I thought .10' would make a difference. (Still trying to figure that one out!)
Is there really that much discretion available on how one determines the BFE at a particular location? On the property in question, a tenth could literally mean the difference between qualifying for a LOMA or not.
I found the following training material on FEMA's site:
UNIT 4: USING NFIP STUDIES AND MAPS
On page 4-7 I found the following:
Here’s the order of precedence for identifying the BFE at a particular location:
¨ The most accurate BFEs are found in the Floodway Data Table (for a riverine
floodplain) and the Summary of Stillwater Elevations table (for a lake). These BFEs
are listed to 0.1 foot. However, the Floodway Data Table is only good for sites on or
next to a cross section.
¨ The next most accurate source of elevation data is the profile. This plot of the crosssection
data is difficult to read accurately.
¨ The least accurate source of elevation data for a riverine floodplain is the FIRM.
BFEs are rounded to the nearest whole foot. However, the FIRM is the only source of
base flood elevations for coastal floodplains and AO and AH Zones.
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Replies
I've found there are two main goals for doing an EC. (Beyond when it's absolutely required by a lender or insurer.)
1) To prove that you are above the BFE and to get a LOMA from FEMA to have the property or structure completely removed from from the flood plain. This puts you out of the 100-year and allows you to get a preferred flood policy. (read: much cheaper!)
2) To prove that although the ground and lowest adjacent grade (LAG) is at or below the BFE, but the lowest finished floor (LFF) is still above the BFE so there's no chance the structure will flood in a 100-year event. This still reduces the cost of flood insurance but not nearly as much as a LOMA.
Of course, my goal would be to LOMA this property out of the floodplain completely.
The property in question is about 600' south of edge of the creek. There are two cross sections that are about 2800' apart - one on either side of the property. The closest one is about 460' upstream from the edge of the property.
It is in the 100-year floodplain, but the lowest adjacent grade is borderline as far as being above the BFE...depending which method you use to get the BFE. Again, we're talking a matter of a tenth or two in either direction. The lowest finished floor is at least 1.5' above the worst case scenario for BFE so there is at least comfort there.
For further comfort, the home was built in 1976 and has never flooded despite numerous 100-year events that flooded other homes in the neighborhood.
I'm just tasked with finding a surveyor who cares enough to look at the big picture and hopefully agree that the Tables are the best source of data.
Lee - it sounds like you understand the source of my confusion. I was always taught to use the most accurate source of information available. In this case, it's my opinion that a tabulated numerical data is more precise than a graph (profile) or rounded up grades on a map.
Brad,
It is my understanding that all the elevations reported on the EC are to the nearest tenth of a foot. For many years EC's and LOMA's out of this office had BFE's that were scaled off of the firm with no complaints from FEMA. A few years ago I had a LOMA kicked back because I had checked the source of the BFE as the Firm. I called the FEMA consultant who was working this case and he told me that we should be using the FIS study and not the Firm, even though as you point out the Firm is listed as a source. So now I use the FIS study to determine the BFE. I would say that if you are at a cross section (I have no idea what they mean by "near") to use the floodway data, it would be more accurate. To get the BFE from the FIS study you have to first determine the river mile location of the structure or upstream edge of the property you are working with. That means scaling upstream or downstream from a known point or cross seciton. Scaling is not an exact science, so anyone who claims to get a BFE in this manner to anything less than a tenth of a foot is fooling themselves. Then you take a shot with the rod at the LAG or lowest point on the property, which as most of us know should only be reported to the nearest tenth, and hope that you have pleased the FEMA gods and your elevation is at least a tenth of a foot above the BFE. One might also contemplate how the original data for the profile was collected back in the early 70's, which was then used to create a model that was laid over a topo (Quad map perhaps?)... I think nearest tenth might be stretching it depending on your % of certainty. Basically you do the best you can with the tools you have available, round to the nearest tenth and hope it works out in you clients favor. At the least if you are not above the BFE doing the EC with help with your insurance rating.
My two cents,
Lee MacDonald, PLS, CfedS, CWRE
Thanks for the quick reply, Pete.
In a way, I've be "interviewing" surveyors and trying to find someone who will at least acknowledge the FEMA material I posted in that it may be acceptable practice to use the Floodway Data to determine the BFE. The answers I get lead me to believe that a lot of them are vastly uniformed on the process and it scares me a bit. As I said, I believe this property may come down to .10' whether the LAG is at or above the BFE....and of course it makes a difference on how they determine the BFE to begin with. It could make a huge difference in the insurance costs and whether I even buy the property in the first place.
From everything I've read, the BFE and surveyed elevations on the EC are reported to the nearest .10'. I have saved all of the LOMAs for the map panel where the property is located and they are all reported to the tenth.
This is in the (north) Houston area. If you have recommendations on someone in the area that you think would take the time to understand my questions and concerns with the process, I'd definitely be interested.
It's funny because I work with surveyors daily and there are about a dozen in my office right now...but our line of work does not require them to be licensed so while they are a good resource for my questions, they can't do much to help me out in the end!
Also, I just took another read through the instructions that are attached to FEMA's EC form. For the BFE field, it states the following:
So even the form itself says it's acceptable to use the Floodway Data Table. Why is it so hard to find a surveyor that understands this?
Hmm...it would appear the forum cut off the bottom of my post...here's the rest:
The part in red is my main concern - primarily the last sentence. What exactly does "on or next to a cress section" mean?
The property in question lies about 600' from the edge of the channel, is definitely in the floodplain and falls between two cross sections. Is it on or next to a cross section?
How does one go about getting an "official" answer to this? I spoke to someone on FEMA's map services/LOMA hotline and she couldn't give me a definitive answer. I've fired off an e-mail to the same department but I'm not anticipating a firm answer, if I even get a response at all.
I'm truly confused.