Floodplain Development: How to Get Approval to Build in a Floodplain

You made the decision to develop a property in a floodplain. You have identified the floodway and floodplain boundaries. Now it’s time to devise a strategy to get approval to build in a floodplain.

In this post, the second of a two-part blog series, we’ll look at how you can modify the floodway and floodplain limits to gain more developable land. We will also walk you through the local and federal approval process required to build in a floodplain.

How to modify a floodway line

This is where you want to start. DO NOT accept the floodway as depicted on the FEMA maps as unchangeable. A closer look may reveal that you can reduce the limits of the floodway to remove a portion or all of your property.

A few things to know about modifying the floodway:

  • Do it early. It’s really the deciding factor in your go/no go process. The location of the floodway can make or break a project.
  • You do not need a development plan to modify the floodway. This is completely independent of what you want to do with the land.
  • A qualified floodplain expert can review available maps and information to determine whether you can modify a floodway line. If they are well versed in the rules of FEMA and follow the guidelines, they can be almost certain it will gain approval, minimizing your risk to move forward. 

 How to modify a floodplain line

There are three ways to determine whether you can move the floodplain line.

  1. Verify with a field survey. This requires land surveyors to prove the area is above the floodplain elevation.
  2. Modify FEMA’s existing conditions hydraulic model. By adding more cross sections to the model, you can tighten the area up and often find it’s possible to move the line.
  3. Create your own hydraulic model. When a detailed study is not available, your consultant can develop one to verify the actual floodplain.

 “All of the individuals at Nave Newell did a tremendous job helping me to modify the official floodplain line on my property and obtain a Letter of Map Amendment from FEMA. They were patient and understanding throughout this long process and I appreciate all of the time and attention they put into this project. I am forever grateful and can now construct a shed on my property.” 

Nate Evans, Residential Client in Montgomery County, PA

How to remove a portion of your property from the floodplain

Using the hydraulic models, your consultant considers a layout and preliminary grading for your development. This allows them to determine what is located in the floodplain and the impact on floodplain elevations. From there, we can make adjustments, running different models/scenarios to maximize the developable area and find the best option. Most likely, there’s a chance to gain more land than you would have thought. However, it does take time and expertise.

You can typically fill some portions of the site, in particular, pads for your proposed structure to get buildings out of the floodplain, without negatively affecting surrounding neighbors.

What’s the approval process to build in a floodplain?

Once you’ve determined your ideal or preferred plan, you will go to the municipality. You may also need to go through FEMA. However, start with the municipality. The process is more complicated, and when they buy into the development, FEMA is more likely to support it.

For redevelopments where structures are already located in the floodplain, the goal is to demonstrate that the improvements will not adversely affect the current floodplain elevations of adjoining properties. For properties where a portion of the site is in the floodplain, your civil engineer will design the site to ensure that the stormwater management controls are out of the floodplain.

What’s the local/municipal process?

Start with zoning relief. It helps to have an expert by your side as you go through this process. Together, with your attorney and civil engineer/floodplain consultant, you can sort out the best approach to obtain zoning relief.

After zoning, you’ll need a grading plan and municipal approval. Municipalities are promoting redevelopment and economic development while at the same time dealing with the real and perceived issues of localized flooding. Having a floodplain expert on your team makes that process easier. Some municipalities will require the submission of a Conditional Letter of Map Revision (CLOMR) to the municipality, as well as FEMA. For smaller streams, if it’s not mapped, you shouldn’t need to go to FEMA, however, the municipality may still require models.

What is FEMA’s process?

If the floodplain is mapped by FEMA, you will need to go through their approval process. You’ll start with the CLOMR and your consultant will model the impact of the proposed conditions. FEMA will then review the models along with various forms and applications. Once they’re in agreement with the study, construction can begin. When complete, your consultant will go back and run the as-built condition through the model, submit to FEMA, and that’s when they actually change the map, which is a Letter of Map Revision (LOMR).

How long does it take to get through the approval process?

Getting the CLOMR approved by FEMA usually takes somewhere between 6-9 months. The good news is that this can take place concurrent with your other land development approvals.

Each site will face different obstacles. As a rule of thumb, if an existing building is in the floodplain, the process will be easier. This is also true if a municipality permits construction in the floodplain. You’ll face the most opposition when looking to develop a piece of vacant land in the floodplain.

Why choose Nave Newell as your qualified floodplain expert?

Our in-house qualified floodplain expert, Paige Maz, PE, knows where to find the right mapping and models. She also knows how to analyze them, adjust them, develop new models, and determine the best way to proceed. She has extensive experience with FEMA and knows how to navigate their entire process while working closely with them.

Paige Maz, PE - Nave Newell's Qualified Floodplain Expert
Paige Maz, PE

Paige has completed hundreds of these studies, specifically on CLOMR’s and LOMR’s. Over the last 20+ years, her efforts have been in the Greater Philadelphia area, including along the Schuylkill River. She has a unique expertise of the process. She knows the steps to approach development in the floodplain effectively, efficiently, and confidently. When big rain events happen, Paige’s models are spot on!

Don’t let a floodplain designation scare you away from an otherwise great development opportunity. Let us show you how to make it work!

Contact Nave Newell for your next floodplain development project.

“This has been a long journey that would have been impossible to navigate without the skillful help of Nave Newell and, specifically, Paige Maz. We are homeowners, not PennDot, so building a bridge isn’t in our wheelhouse. The process is complicated, confusing, frustrating by nature, and time consuming. NN and Paige were able to outline the procedure to us in a way that made sense, then act as the point person to accomplish everything required to get that done. Our bridge crosses a floodplain (see below) and Paige’s expertise in construction in this environment was crucial in getting approval for the project.

We attempted to build this bridge before using another engineering firm, but abandoned that effort because the drive by that company to see the project through simply was not there, so the project was perpetually in limbo until we finally gave up. That was not the case with NN and Paige. This was almost personal with this firm. They were determined to get this project approved. You will not be lost in the shuffle if you allow NN and Paige Maz to plan and execute your project.”  

– Jay Rowan VMD and Erin Downes VMD, Residential Clients in Chester County, PA
Bridge construction over a floodplain