In Harm’s Way – To Build or Not to Build?
Texas and Maryland represent opposite ends of the political spectrum. So, it’s not too surprising that floodplain regulations in the two areas differ radically. When it comes to building in harm’s way, most municipalities and counties in the Houston region allow development in the floodplain with certain precautions. But several counties in Maryland prohibit floodplain building altogether. One even requires developers to deed floodplain land to the county.
In contrast, Texas developers even fight for the right to build in floodways!
The right to develop floodway land in the left foreground above was the subject of an eight-year lawsuit between a developer and the City of Houston.
Let’s examine the differences more closely.
Floodways vs. Floodplains
FEMA defines a floodway as the main channel of a river PLUS adjacent land that must remain free of development in order to avoid flooding areas upstream.
A floodplain extends farther out, usually to the edge of a valley. Floodplains flood repeatedly. Frequency and depth depend on rainfall and elevation within the floodplain. The area in the photo above flooded 53 times since Lake Houston was built 67 years ago. It even flooded SIX times in ONE year.
Houston Building Regulations
During Harvey, more than 150,000 structures in Harris County flooded. The area shown above went under 28 feet of water.
After Hurricane Harvey, Houston made its building regulations in floodplains more stringent. This table by the engineering firm WGA summarizes the changes.
The idea: by building higher, you build safer.
Regulations also address the foundation type and “fill” practices.
- Unlike a slab, pier-and-beam foundations typically let water flow under a house.
- “Zero net fill” prohibits elevating a home by bringing fill dirt in from outside the floodplain.
However, builders can still move dirt around inside the floodplain. They use a practice called “cut and fill.” Example: they take dirt out of a stormwater detention basin and use it to elevate slabs. That way they don’t reduce the area available to store floodwater.
These regulations do nothing to make homes already built in a floodplain safer. They only affect new building.
And they only make people safer to the extent that engineers can accurately predict the future. The future includes both rainfall and upstream development.
In the case of Harvey, remember that FEMA had revised flood maps just 10 years earlier. Now it’s revising them again.
The point: under the “there are ways to build here safely” philosophy, your “safety” is based on imperfect knowledge, changing conditions, changing regulations and shifting estimates.
Sample Maryland Regulations
Maryland takes a different approach to building in harm’s way. It says “Don’t.”
The State of Maryland provides model floodplain regulations. Section 4.2(b)1 states: “Subdivision proposals shall be laid out such that proposed building pads are located outside of the special flood hazard area and any portion of platted lots that include land areas that are below the base flood elevation shall be used for other purposes, deed restricted, or otherwise protected to preserve it as open space.”
Counties and Communities implement their own floodplain regulations. I haven’t checked every county, but found that Howard County:
- Prohibits any new structures in the 100-year floodplain. See page 152.
- Requires subdivisions to either a) deed land in floodplains to the county or b) grant floodplain easements to the county. (Page 136)
- Prohibits storing building materials in a floodplain. (Page 136)
- Prohibits clearing, excavating, filling or altering drainage in floodplains. (Page 136)
- Will not issue variances for projects within floodways that result in any flood discharge levels (Page 139)
Montgomery County, Maryland, has prohibited residential development in 100-year floodplains since 2007. (Page 4).
Frederick County, Maryland, states that no development has occurred in its floodplains in the past 10 years.
Two Different Philosophies
The Texas philosophy says, “There are ways to build safely in flood-prone areas.” The Maryland philosophy seems to say, “It’s safer not to.”
It’s difficult to say objectively which is better/safer. The regulations are designed for different different people in different areas: Rural vs urban. Hilly vs. flat. Temperate vs. Subtropical.
But I will say this. As I read Howard County’s Hazard Mitigation Plan, the number of homes that could be damaged in a 100-year flood – ten – and a 500-year flood – twenty – shocked me. (Page 39). Compare that to the 154,000 structures damaged in Harris County during Harvey. Well, no, don’t. There is no comparison.
Posted by Bob Rehak on 12/4/2022
1923 Days since Hurricane Harvey
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.