At least part of Madera, a new 1,700-acre development in Montgomery County that straddles FM1314 immediately north of SH242, is being built on wetlands and is in a 10-year flood zone.
US Fish & Wildlife Map Shows Wetlands Dot Development
From US Fish & Wildlife Service National Wetlands Inventory. Madera will stretch past the left/right edges of this picture north of SH242 (the east/west highway near the bottom.) FM1314 bisects pictures from N to S in middle.
FEMA’s Base Flood Elevation Viewer Shows Flood Risk
From FEMA’s Base Flood Elevation Viewer. Extent of 100-year flood zone shown on left. 10-year flood zone shown on right.
Note that this survey shows only about a quarter of Madera (see below). The survey stops abruptly on the western margin. So, it is hard to say with certainty how bad flooding is throughout the rest of the site.
Yellow outline shows approximate outline of FEMA BFE survey shown above within Madera tract (black/white outline).
Option to See Depth of 100-Year Flood Waters
Also note that the purple area shows only the extent of 100- and 10-year floods. However, within the FEMA BFE viewer, you also have the option to select a layer that illustrates the depth of 100-year floodwaters. See below. (FEMA does not offer the option to show the depth of 10-year floods.)
Limitations of BFE Viewer
Of course, FEMA shows “estimated conditions” before developers bring in fill and alter drainage. But notice how a pre-existing development near Madera would fare in the same 100-year flood. You can see the close-up below just above SH242 near the right edge of the image above.
FEMA shows that most homes in this development are still in the flood zone and would still flood to a depth of 1-2 feet in a hundred-year flood.
The street leading out of the development to SH242 could be under more than FIVE FEET of water in places!
FEMA Base flood Elevation Viewer
FEMA’s “Estimated Base Flood Elevation” is “The estimated elevation of flood water during the 1% annual chance storm event.” Structures below the estimated water surface elevation may experience flooding.” A 1%-annual-chance flood is also known as a 100-year flood. FEMA defines properties with a 1% annual chance of flooding as having “high flood risk” and says they have a 26% chance of flooding during the life of a 30-year mortgage.
Purposes of BFE Viewer
The agency developed its Base Flood Elevation viewer with several purposes in mind. To:
- Inform personal risk decisions related to the purchase of flood insurance and coverage levels.
- Inform local and individual building and construction approaches.
- Prepare local risk assessments, Hazard Mitigation Plans, Land Use Plans, etc.
- Provide information for “Letter of Map Amendment” (LOMA) submittals.
A LOMA lets the developer of a subdivision change the depiction of how flooding affects his/her subdivision. It’s the key to offering up-to-date risk assessments.
Full BFE Reports Available
FEMA also lets you download or print full BFE reports that give more specific estimates of flood depth at exact points, not just within a wide area.
At the point shown above, you could expect 4.2 feet of water above the land surface in a 1%-chance flood. For the full report, click here.
Here’s what that point looked like last Saturday (1/22/22) from the air.
Madera development today at FM1314 and SH242, the point shown in BFE report above.
Cross-check this area on the maps above for wetlands and swamps! Then you can see why it’s so soupy.
BFE, Fill Not Mentioned in Drainage Analysis or Construction Plans
Text searches of Madera’s construction and drainage plans showed no references to “BFE” or “base flood.”
It seems unlikely that a “cut and fill” operation could excavate enough dirt from Madera’s drainage channel (dotted blue line with red parallel lines) and detention ponds to raise the whole site out the hundred-year flood zone. Five feet is a lot of fill for a 1700 acre site.
To raise a site this large, contractors would likely have to bring in fill from outside the property. But a text search from the word “fill” did not turn up any exact matches either.
So maybe they’re just planning to create the world’s biggest drain and hope to carry water off before it can reach homes.
However, a summary of the Madera master drainage plan notes…
“Coordination with MCED [Montgomery County Engineering Department] and adjacent property owners is recommended … on the potential need for inundation easements.”
Revised Channel Alignment Memo, 2/19/21, Page 11
Still, engineers for the development claim it will have “No adverse impact.”
To review Montgomery County regulations regarding flood zones and drainage, see the documents under the “Construction Regs in Flood Hazard Areas” tab on my reports page. You’ll see plenty of opportunities for improvement.
Posted by Bob Rehak on 1/27/22
1612 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.