Odom lake Swamp Archives - Reduce Flooding

Yesterday, I posted about the discovery of something called the Odom Lake Swamp on a 70-year-old map. Many of the homes that flooded in Elm Grove on May 7 were built in or near it. But learning that required scaling and aligning maps in Photoshop. It’s a time consuming process and not everyone has Photoshop. If you’re considering buying a piece of property, luckily, there’s an easier way to check on its past: the history function in Google Earth Pro.

History Function In Google Earth Pro

Google Earth Pro contains dozens of aerial and satellite images that are already scaled and aligned. The program is a free download and makes scrolling back through time simple. When you first open the program, you’ll see a map of the world. Click on the area that interests you to zoom closer in steps.

Then:

From the menu at the top of the screen, select “View/Historical Imagery”
Click on the Clock icon in the menu bar.
Arrows and a timeline will appear at the top left of the screen.
Scroll back and forth through time by clicking on the arrows.
To show streets that exist today (but that didn’t exist when the image was taken), select View/Sidebar. Then check Labels/Borders and Roads.

Here’s what you see when you scroll back to 1978 (minus the red circle which I added to highlight the area of interest).

Looking at this, you wouldn’t have known that the large flat, featureless area was called Odom Lake Swamp. But you could tell that something unusual was going on there. And that might tell you to dig further into the area’s history.

“Reading” Satellite and Aerial Images

Google Earth Pro doesn’t show contour intervals as a topographic map would. Nevertheless, it can still tell you a lot. Flat featureless areas like this in the middle of dense forests can indicate ponding, at least on a seasonal basis. Translation: Low area.

Note several other discontinuities in the image above:

A small pond in the lower left (north of Sherwood Trails)
A depression near the upper left that interrupts the straight white line
A triangular area in the upper right where no trees are growing.

In the image below, I zoomed in closer on the Odom Lake Swamp. The image shows what at the time was a dry lake bed. Taylor Gulley had just reached the area and had most likely drained what was a seasonal pond or swampy area. Taylor Gulley itself (bottom right) had not yet been excavated to the county line (thin green diagonal line in upper left).

Close up of Odom Lake Swamp. Taylor Gulley at the bottom was still under development at the time of this image in 1978. Streets had not yet been built in this area. The white lines show where streets are today.

Nature Never Forgets

As one expert told me: “Where old channels, swamps, meanders, etc. were filled in, during major floods, water always seeks the lowest point. Even if you fill in an area, it usually is still the lowest point of a larger area (or watershed) and during large rain storms, the water finds its way there.”

It only takes a one degree slope to make water move across concrete (two degrees through grass or foliage). That’s barely visible. It underscores the need to consult maps and tools like Google Earth when buying property.

Awareness of potential problems is your best way to prepare for or avoid them.

Google Earth can help in this regard. As does FEMA’s National Flood Hazard Layer Viewer.

Posted by Bob Rehak on 6/20/2019

660 Days since Hurricane Harvey

A 1949 map of the area now called Kingwood reveals that the homes in Elm Grove that flooded on May 7 were built in something once called the Odom Lake Swamp. It turns out, “Nature never forgets.”

*Area of interest for this discussion is circled in red.*

I previously posted about this map in the context of how the West Fork has shifted over time. At the end of the post, I asked readers to write me if they found anything else interesting. One did. And it was a very interesting indeed.

He pointed to the area circled in red above. When I superimposed that over the present-day image below, my jaw dropped.

*Same general area that was superimposed over old map.*

It’s True. Nature Never Forgets

The area labelled Odom Lake Swamp matches very closely the outline of the May 7 flood in Elm Grove that damaged almost 200 homes.

*I used the county line and the confluence of the East and West Forks to align the two images, then cropped this out of the center.*

*The reader who reported this came up with a slightly different map that shifts the label “Odom Lake Swamp” to the west side of Village Springs. I am not sure what alignment points he used*, *but his work and mine closely match.*

At a Houston Geological Society seminar on flooding that I attended last year, I remember several speakers talking about this phenomenon, including former Harris County Judge Ed Emmett. During heavy rainfalls, water gravitates toward its original channels.

One expert, who talked to me on condition of anonymity because of the lawsuits swirling around this issue, explained it this way. “Where old channels, swamps, meanders, etc. were filled in, during major floods, water always seeks the lowest point. Even if you fill in an area, it usually is still the lowest point of a larger area (or watershed) and during large rain storms, the water finds its way there.”

Current Flood Map Echoes 1949 Map

He attributed the Elm Grove flooding to a combination of clear cutting without mitigation upstream, heavy rainfall, and lower elevation. In fact, FEMA’s National Flood Hazard Layer Viewer shows that this part of Elm Grove is in the 100-year (aqua) and 500-year flood plains.

*2007 (most recent) flood plain map for Elm Grove, Mills Branch, Woodstream and Royal Brook* *subdivisions*.

Implications

I’m not a lawyer and I don’t give legal advice, but it seems to me that this finding does little to change the legal lay of the land (no pun intended).

The residents south and east of Woodridge Village, despite being lower than surrounding areas, had never flooded before – even in Harvey.

They didn’t flood until the developer clearcut 268 acres, filled in natural streams, eliminated wetlands that act like natural detention ponds, and graded the property toward the area that flooded. All without constructing detention ponds until AFTER people flooded.

Had those ponds been in place, they should have held 13 inches of rain (a 100-year) rainfall. We didn’t get that much. The gage at US59 recorded 6.24 inches on May 7 over six hours. The heaviest rain fell during the noon hour when we got 3.64 inches.

*From HarrisCountyFWS.org* *for May 7. The other official nearby gage at West Lake Houston Parkway received less rain that day.*

Harris County meteorologist Jeff Lindner characterized the May 7th event as somewhere between a two and 50-year rain. Experiment with the different possibilities on the chart below.

*NOAA Atlas 14 precipitation frequency chart.*

Ten Lessons of May 7th

So aside from the Odom Lake Swamp being a historical curiosity, what can readers learn from this.

Flooding doesn’t always come from the river. Streets can flood homes when the rainfall rate exceeds the capacity of storm drains.
Before you buy a home, check historical maps. Learn whether the developer filled in lakes, ponds, swamps, or wetlands and then built your home on top of them. Remember: Nature never forgets!
If the answer is yes, question how much you want the property. Use the knowledge to negotiate a discount with which you can purchase flood insurance. That’s the best way to discourage unsafe development practices.
If you live downstream of an undeveloped area, be aware that floodplains are a shifting target. Just because you’re NOT in a floodplain today is no guarantee that you won’t be tomorrow. Upstream development can cause downstream flooding. So watch carefully.
Pay no attention to anyone who says, “Oh, that area will never be developed.” The more worthless the land, the bigger the profit potential.
If you live in this area, get flood insurance.
If you buy a low-lying home, be prepared to have your life disrupted.
Buyer beware.
Pressure your elected representatives to turn areas such as Woodridge Village into park land. When it was wetlands, it protected the people downstream from flooding and provided recreation.
Buying the property north of Elm Grove could have cost less than the damage to one home. (See appraisal below). Not buying the property was a costly decision.

*Ironically, the Montgomery County appraisal district values the 60+ acres of land north of Elm Grove at about a quarter million dollars.*

Posted by Bob Rehak on 6/19/2019

659 Days since Hurricane Harvey

Tag Archive for: Odom lake Swamp

Google Earth Pro: Another, Easy Way to Check on a Property’s Hydrologic History