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Old 11-19-2009, 12:09 PM
 
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Could someone please help me to interpret the flooding information provided by FEMA?

How would one compare areas marked blue (1% floodplain (FEMA zone AE) and areas marked gray on the map - is marked gray what is protected by levee? In other words, staying in "gray" is better than staying in "blue" from a potential flood perspective, right?

the source is here

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Old 11-19-2009, 01:14 PM
 
Location: San Antonio/Houston
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Staying in gray is better than staying in blue. Dark blue is the worst.
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Old 11-19-2009, 01:21 PM
 
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Quote:
Originally Posted by elnina View Post
Staying in gray is better than staying in blue. Dark blue is the worst.

That's what I thought. What about the red lines coming from the river? Is it a potential 100 year water mark? Or a water direction?
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Old 11-19-2009, 01:48 PM
 
Location: Houston, TX
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Live in the gray areas...you will have to pay more for flood insurance in the blues
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Old 11-19-2009, 02:08 PM
 
Location: The land of sugar... previously Houston and Austin
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Yes, but keep in mind several other large areas do have levees, but aren't showing up in gray yet because the status hasn't been updated, or something of the sort. The disclaimer is in there. New Territory and Pecan Grove are a few of those. Also, the land was all mapped several years ago so new subdivisions/areas less than a few years old may not be accurate on here.
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Old 11-19-2009, 06:48 PM
 
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Quote:
Originally Posted by AK123 View Post
Yes, but keep in mind several other large areas do have levees, but aren't showing up in gray yet because the status hasn't been updated, or something of the sort. The disclaimer is in there. New Territory and Pecan Grove are a few of those. Also, the land was all mapped several years ago so new subdivisions/areas less than a few years old may not be accurate on here.
Is it both, New Territory West and East? Or only East?
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Old 11-21-2009, 01:18 AM
 
Location: Sugar Land, TX
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In 30 years, I've never seen any residential flooding in Sugar Land. But it's also been a while since the Brazos River flooded really bad. Years ago, I remember seeing it so high that it almost came up to the bottom of the 90A bridge at Richmond. This was before all of the Greatwood/New Territory developments that are so close to the Brazos. If I were going to worry about flooding, I'd stay out of the zones close to the river (in the blue). Hopefully the levee system will do the job..... but we do tend to get 500 year floods every 10 years here in Houston.
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Old 11-21-2009, 10:26 AM
 
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New Territory on both the East and West Sides have never flooded. Over the past year, New Territory has raised the retaining walls around the community to stay out of the flood plain.
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Old 11-21-2009, 11:58 AM
 
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As best as I can determine, if you're inside a zone identified as "protected by levee(s)" FEMA has removed that area from the 100-year flood plane and you're eligible to buy flood insurance at a reduced rate. It doesn't mean you're safe from flooding, just more protected than if you were not protected by a levee. But the Brazos is not the only flooding you have to worry about either.

FEMA and Ft. Bend County jointly started remapping Ft. Bend County in 2004-5-ish, which was the first update in decades. The remapping included use of modern technologies (like LIDAR) that meant the new maps were much more accurate in measuring elevations.

At the Richmond gauge (at the Brazos River Bridge) the Brazos enters flood stage at 48', and is at "major" flooding at anything over 50'. For comparison purposes, at Richmond the river is usually about 12-13 feet deep.

The Brazos has flooded at Richmond at least a couple of times that I can remember in the last 35 years, and it will happen again. The last time I can remember the Brazos in major flood stage at Richmond was in the early 90's, and I think it happened before that in the mid-to-late 80's as well (can't recall the year, but sure it was before 88 as a friend living in Thompsons was flooded out of his home sometime before the end of 88). That affected people living close to the river.

After the initial map data was available from the remapping (but not finalized), some of the levees were deemed to be insufficient to protect against 100 year flooding. The deficiency was measured in inches, but it was enough to exclude those areas from FEMA considering them to be protected. They came in and raised the levees in First Colony (and I think at least parts of Riverbend if not all of it) by a foot, which should put them all well over what FEMA requires. That was done 2007-ish.

As late as September 2008, the maps were still not finalized. The levees had all been raised but the county asked for an extension to finalize their preliminary mapping data. I think the maps you linked to are the county's final version of mapping data submitted to FEMA, but may not be FEMA's final accepted version. Really not sure about that though.

Personally, depending on how you draw a line between my house and the Brazos, I'm behind at least two levees and right on the edge of "it just doesn't flood here" territory. So I think that there will be at least a couple of soup bowls full of houses underwater before the Brazos ever gets to me.

So, I'm not all that worried about the Brazos. But I still have flood insurance.

If you look at the flood maps you will see the area is full of drainage ditches, creeks, dams and man-made retention lakes. They're not there to look pretty, they are part of the flood control system. Not for the Brazos, but to run rainwater off from the neighborhoods through the system and eventually into the Brazos. Extremely heavy rains (Tropical Storm Allison - Wikipedia, the free encyclopedia) can put a heavy burden on that system. Allison hit Ft. Bend County the day before it unleashed flooding in Houston, and it was several inches less here than in Houston, but still the lake next to my house was within a foot of coming over into the street. The flow from the streets to the runoff drain into the lake was backed out into the street by almost a foot. Neighbors living two blocks away from me (and the lake) had street flooding approaching their front doors.

I have no way of knowing what it would have looked like here if we had gotten all the rain that Houston got the next day, but for a few hundred bucks a year I have flood insurance and I think it's worth it.
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