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Floodplain Development: What You Need to Know Before You Build

Did a floodplain designation scare you away from an otherwise great development opportunity?

Waterfront properties have a tremendous amount of curb appeal. However, the threat of flooding can also be a deterrent for many real estate developers.

If you have the right project and the right expertise, you can develop in a floodplain, and it can be a great investment.

In this two-part blog series, we’ll look at development in the floodplain and Nave Newell’s floodplain expert, Paige Maz, PE, will answer some common questions.

How do I know if a property is in a floodplain?

For larger streams and rivers, you can look at the Federal Emergency Management Association (FEMA) – Flood Insurance Rate Maps (FIRM). While this is a good starting point, if you’re in the floodplain, it doesn’t necessarily mean the property is undevelopable.

If you’re near a small stream, it is possible that a FEMA study does not even exist. In either case, you want to consult a qualified floodplain expert. They will verify what you can do with a property and identify next steps.

What’s the difference between a floodplain and a floodway?

Simply put, you can develop in one and not in the other.

floodplain, as defined by FEMA, is any land area susceptible to flooding. A floodplain designation doesn’t necessarily mean you can’t develop a property. While some developers may immediately disregard it, prime properties are tough to come by these days, and it’s often worth a second look.

floodway is the stream channel and adjacent land kept free of development, in order to maintain the flood carrying capacity of the stream. Per regulations, you cannot develop in a floodway. This area must be clear of buildings, other structures and fill, so that increases from any development in the 100-year floodplain are minimized.

Is it possible to modify floodplain and floodway lines?

YES!

It is possible that the floodplain and floodway lines were mapped incorrectly or that conditions have changed over time. An updated land survey and analysis can verify the accuracy of the map. Sometimes it’s as simple as getting a survey to identify a portion of the property that can be removed from the floodplain.

The key is working with a consultant who has the expertise to understand floodplains, and the knowledge and ability to model and change the floodway or floodplain line through FEMA.

How do I determine if development in a floodplain is viable?

First, consult a qualified floodplain expert.

You have questions:

  • Can I build on this site?
  • How much usable ground do I have available?
  • What’s it likely to look like during a big storm event?

An expert can answer them for you!

As long as the area you want to develop is outside the floodway, it is viable. Through our own study and analysis, we can get a more precise picture. Above all, we can determine if line adjustments are possible to allow for more developable land.

We can show you how to maximize your property in the floodplain.

In our next post, we’ll cover how you get approval to build in a floodplain.

Have questions? Ready to talk?

Contact us if you’re ready to talk to a qualified floodplain expert.

Feature Image Credit: Venice Island Townhouses - Varenhorst. 
For a previous developer, Nave Newell's floodplain expert, Paige Maz, PE, obtained a Letter of Map Revision (LOMR) to shift the floodway and gain developable land on this site. For this project, we modeled the proposed townhomes, to demonstrate the impact on the Schuylkill River floodplain elevations to the City of Philadelphia. 

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