I have a friend who is fond of saying, “If rain falls on your roof, you need flood insurance.” Here are two telling statistics from the final Harvey report issued by Harris County Flood Control that dramatize that point. But there’s more than one type of flood insurance.
In Harvey, Two-Thirds of Flood Victims Had No Insurance
Of the 154,170 estimated homes flooded across Harris County from Harvey, only 36% had active flood insurance policies in place.
Of those 154,170 homes flooded, 105, 340 were outside the mapped 1% (100-yr) floodplain – 68%.
From these two statistics, you can tell that people thought being outside a mapped flood zone meant SAFETY. You can also see how tragically wrong they were.
Virtually ALL Humble Area Retired Teachers Have Flood Insurance
Monday morning I gave a talk to the Humble Area Retired Teachers Association (HARTA). There were probably 150-200 teachers in the room. I asked for a show of hands to see how many had flood insurance. Virtually every hand went up. Given the aforementioned statistics, this SHOCKED me.
There are two possibilities.
People learned a lesson from Harvey and Imelda.
The teachers in the room were smart!
I’m sure it’s a combination of both in this case. Teachers tend to be fast learners. But it was such a pleasant surprise. They set a great example for everyone!
FEMA needs to study HARTA to find out how to market flood insurance to the rest of the world.
Static Maps in a Changing World
How could the flood maps during Harvey have been so far off? It was a combination of things.
Of course, Harvey was a far larger-than-normal storm – the biggest ever to hit the continental US.
Second, flood maps are a stationary snapshot in time. They assume nothing changes.
But we also know that things DO change:
The river changes every time it floods.
There has been massive development upstream from us in Montgomery County in the last two decades.
Conroe has been one of the fastest growing cities in America.
That development increases runoff, shortens the time of accumulation for floodwaters, and causes higher flood peaks.
The one thing that hasn’t changed: Montgomery County flood maps. The County has not updated the data behind them since the 1980s. Parts of the county remain unmapped. And the County does not even employ a surveyor, according to an inside source.
Radical Example of Impact of Upstream Development
Uncontrolled upstream development can totally change the game. Here’s a personal example.
Back in 1980, I bought a home on Spring Creek in the Dallas area. It was built two feet above the hundred year flood plain. The next year, developers built the 250-acre Collin Creek Mall upstream from me in Plano. The creek behind my house started flooding on minor rains of less than a half inch. A three city commission between Garland, Richardson and Plano asked the Army Corps to investigate.
The Corps found that I was now 10 feet BELOW the 100-year flood plain instead of two feet ABOVE it. A 12-foot delta!
That’s how radically and quickly things can change from upstream development as the people in Elm Grove discovered.
Elm Grove’s Game Changer: Woodridge Village or what some now call “Village of the Damned“
New Flood Maps Being Developed
NOAA’s new Atlas-14 Rainfall statistics for this area are causing flood maps to be redrawn. The statistics reflect about 40% more rain for a 100-year flood. That means flood zones will expand.
When released in the next year or two, the new maps will open a lot of eyes for people who have not yet purchased flood insurance.
Net: If you don’t have flood insurance, get it.
Another Type of Flood Insurance
That brings us to another type of flood insurance not covered by FEMA’s National Flood Insurance Program. It’s the kind of insurance that comes from situational awareness and community engagement.
The more aware we are of the causes of flooding…
The more engaged we are as citizens…
The more we insist that developers follow best practices…
…the safer we become.
NFIP insurance will partially reimburse you if you flood. But awareness and activism may keep you from flooding in the first place. We need both types of insurance. One without the other is a recipe for disaster.
We should not assume that some benevolent government agency in Montgomery County is watching over new development, protecting us. They are not. Period. They have other priorities and protecting downstream residents is rarely one of them. Even though Harris County is redrawing its flood maps, Montgomery County is not. That will make MoCo’s even MORE OUTDATED. That’s why we need vigilant, involved citizens.
Need Regional Flood Control
And even more, that’s why we need regional flood control, much as we have regional groundwater control. With groundwater withdrawals, one conservation district must get its plans approved by neighboring districts. Wouldn’t it be beautiful if we had a similar arrangement for flood control?
Posted by Bob Rehak on 2/11/2020
896 Days after 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.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/01/20200120-RJR_7283.jpg?fit=1200%2C800&ssl=18001200adminadmin2020-02-10 22:36:552020-02-11 11:39:35Flood Insurance: Two Types
Jeff Lindner, Harris County Meteorologist but put this notice thus morning. He said wet weather will persist until mid week.
Slow-Moving Cold Front Stalls Out
A slow-moving cold front currently extends from Longview to north of Austin and is creeping southward. Ahead of this boundary a warm and moist air mass covers all of SE TX this morning. Meanwhile, north of the boundary a colder and somewhat drier air mass is in place.
Radar is fairly calm this morning with a couple of lines of showers lifting north over the region in the warm air advection pattern in place.
Surface cold front will move to near a Madisonville-to-College-Station line later this morning and then likely stall in that region today. Focus for rainfall today will be mainly across the northern half of the region closest to the front. Rainfall amounts today could average 1-2 inches north of HWY 105 as another upper level disturbance approaches from the WSW and interacts with the slow moving front.
Front Pushes South Tonight
Front will get another push this evening and likely progress southward toward the coast tonight. With the afternoon and evening short wave disturbance moving off to the ENE expect a lull in any heavier rains by late evening across the northern portions of the area.
Mainly light showers will impact the southern portions of the area this evening and overnight as the surface front stalls near the coast.
Tuesday Front Lifts Back North
On Tuesday the surface front begins lifting back northward as a warm front with a continued chance of showers over the area.
A strong upper level storm system currently digging into NW Mexico will begin to move slowly eastward and toward TX late Tuesday into Wednesday. This will result in the formation of a surface low pressure system over the coastal bend of TX Tuesday night which then moves ENE/NE across SE TX Wednesday.
Showers and thunderstorms will be likely in this period with some heavy rainfall possible.
Clearing Late in Week
This surface low will be strong enough to finally push a stronger front through the region and clear the area out for at least a couple of days before clouds and rain chances return for the weekend.
Yo-Yo Temperatures
Temperatures will be all over the place with the surface front stalling and then creeping across the area. Ahead of the front temperatures will be in the 70’s and then fall into the 60’s and possibly 50’s behind the boundary.
Rainfall 1-4 Inches, Highest to North
Rainfall Amounts:
Fairly tight rainfall gradient will setup across SE TX over the next 72 hours with much of the rainfall occurring north of HWY 105 and much lower amounts near the coast.
Storm total rainfall amounts through Thursday morning will likely average 1-2 inches over much of the region north of I-10 and 3-4 inches in the Lake Livingston area.
South of I-10 amounts of .50-1.0 inch will be possible. While the drought monitor shows dry conditions over much of the area, the time of year combined with lack of any vegetation growth and the widespread nature of the expected rains suggest rises on area creeks and rivers will be likely.
Highest impacted watersheds look to be the mainstem and tributaries of the Trinity River and the San Jacinto basin.
Currently predicted amounts are spread out enough to preclude any forecast to reach flood stage, but we will need to watch rainfall trends today and again on Tuesday especially north of HWY 105.
Should rainfall totals begin to pile up in our NE counties (Polk, Trinity, Houston, San Jacinto) a flash flood watch could be required for those areas.
Excessive Rainfall Outlook (Monday):
The Lake Houston area has only a marginal to slight risk of excessive rainfall today.
Excessive Rainfall Outlook (Tuesday):
Tuesday, the risk for excessive rainfall in our area looks mostly marginal.
Day 1-3 Forecast Rainfall Amounts:
Rainfall in the 3 day period should total 1-4 inches. Higher totals to the north. Lower to the south.
Posted by Bob Rehak on 2/10/2020 with thanks to Jeff Lindner
895 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/02/image003.gif?fit=748%2C562&ssl=1562748adminadmin2020-02-10 07:41:592020-02-10 07:47:23Rain Forecast This Week
Here’s a construction update for Perry Homes’ Woodridge Village, the stalled development implicated in flooding Elm Grove and North Kingwood Forest twice last year.
On January 25, 2020, I flew over Woodridge Village. Not much had changed since my December flyover. However, Perry Homes, had concreted about 280 feet of Taylor Gully on the east side of the development facing North Kingwood Forest. And they started to build a berm between Woodridge Village and Elm Grove. Finally, they have started prep work for building more streets. See images below.
Overview of Construction Activity
Homes in North Kingwood Forest (bottom right) flooded twice in 2019 when water from the Taylor Gulley channel behind them overflowed.In December and January, Perry Homes, the ultimate developer of clearcut area called Woodridge Village, lined a portion of that channel with concrete.Closer View: Perry Homes also erected a berm along the southern edge of the kite-shaped S2 detention pond. Note the lack of activity above the pond.
Slanting Berm Between Elm Grove and Woodridge
Since the January flyover, Perry Homes has continued to build up a berm south of the S2 detention pond. The height of the berm is about 3-4 feet immediately west of Taylor Gulley (grassy channel in lower right). It tapers down to nothing before you get to Fair Grove Drive, one long block to the west (out of frame to the left in picture above).
Note height of berm at end of Village Springs Drive, adjacent to Taylor Gulley.Erosion from berm is already starting to collapse silt fence in numerous areas.Photo taken 2/8/2020.Looking east from opposite end of pond. At Fair Grove Drive, the berm is below the level of Elm Grove homes behind the tree line on the right.Photo taken 2/8/2020.
Whether Perry intends to build up the western portion of the berm is unclear. If they intend to go west beyond the point above and continue the berm south of the S1 pond, they have not yet done so.
The Strange Case of the Elevated Swale
Perry Homes has now dug a ditch at the peak of the berm to act as a backslope interceptor swale. Such a swale is designed to reduce erosion on the slopes of a detention pond by channeling water through pipes instead (note concrete opening of one such pipe in distance).Photo taken 2/8/2020.
Originally, I thought the berm might be the missing maintenance road that Montgomery County regulations specify around detention ponds. However, yesterday, Perry Homes’ contractor etched a ditch in the middle of the berm. I guess this ditch will act as the backslope interceptor swale, another requirement of detention ponds in Montgomery County.
Such swales channel water into ponds through pipes installed at low points. Their purpose: to prevent runoff from surrounding areas from flowing over the edge of ditches and causing erosion.
Except in this case, water from the surrounding areas would have to flow uphill several feet to get to the swale. So the swale will only channel water that falls directly on it.
No New Detention Ponds
No new detention ponds have been created since last August.
Prep Work for New Streets
However, Perry Homes is starting to add new storm drains to areas where roads have not yet reached on the north side of the S2 detention pond.
Storm drains being added to the north side of the S2 detention pond. Photo taken 2/8/2020.Note rilling (erosion) along side of pond.
Perry Had Promised No New Streets Until All Detention Ponds In
Point #1 in Perry Homes’ letter to the City Attorney about remediation efforts promised that Perry would delay additional street construction until three detention ponds on the northern part of Woodridge Village were complete. But as you can see from the first photo above, no additional detention ponds have even been started on the northern portion of the site.
Possible Impact of Changes on Flooding
The concrete channel will reduce erosion, but will do nothing to reduce flooding. As you can see from the video below, taken by Jeff Miller after a minor rain, Perry Homes needs the three additional detention ponds they promised in 2017, two and a half years ago, to reduce flooding.
The berm may redirect flooding. The berm has the potential to change the location of flooding. As floodwaters build up in the S2 pond shown above, they will eventually rise above the overflow channel between the concrete portion of Taylor Gulley and the pond. When that happens, the water will go around the berm. It could happen on two sides. On the west at Fair Grove (above) and on the east at Taylor Gulley (below).
Video by Jeff Miller after light rain on Jan. 28th shows flow from north side of Woodridge Village into Taylor Gulley. There should be a massive detention pond beyond the black fence.Taylor Gully concrete channel is approximately one-third fullon about a third of an inch of rain before this point in the day.See graph below. Photo taken around 5pm.The closest official gage at West Lake Houston Parkway showed 0.32 inches of rain before Miller took the photo above.
On the east side of the concrete portion of Taylor Gulley, notice how the edge slants down toward North Kingwood Forest (out of frame on the right).
Note levels on either side of the concrete culvert shown in aerial photos above. S2 detention pond is out of frame to left and North Kingwood Forest to right.Photo taken 2/8/2020.
Once floodwater gets into North Kingwood Forest, experience has shown that it will flow through streets into Elm Grove, bypassing Taylor Gulley.
Storm sewers, once connected to the detention ponds, will simply shorten the time of accumulation after heavy rains and fill the ponds even faster. That usually results in higher peaks. Again, without additional detention, there is no flood-reduction benefit for downstream residents.
Posted by Bob Rehak with help from Jeff Miller on 2/9/2020
894 Days after Hurricane Harvey and 143 after Imelda
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.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/02/20200208-RJR_7558.jpg?fit=1200%2C800&ssl=18001200adminadmin2020-02-09 14:30:152020-02-10 06:47:08Construction Update: Perry Homes Adding Storm Sewers, Berm to Woodridge Village
Flood Insurance: Two Types
I have a friend who is fond of saying, “If rain falls on your roof, you need flood insurance.” Here are two telling statistics from the final Harvey report issued by Harris County Flood Control that dramatize that point. But there’s more than one type of flood insurance.
In Harvey, Two-Thirds of Flood Victims Had No Insurance
Of the 154,170 estimated homes flooded across Harris County from Harvey, only 36% had active flood insurance policies in place.
Of those 154,170 homes flooded, 105, 340 were outside the mapped 1% (100-yr) floodplain – 68%.
From these two statistics, you can tell that people thought being outside a mapped flood zone meant SAFETY. You can also see how tragically wrong they were.
Virtually ALL Humble Area Retired Teachers Have Flood Insurance
Monday morning I gave a talk to the Humble Area Retired Teachers Association (HARTA). There were probably 150-200 teachers in the room. I asked for a show of hands to see how many had flood insurance. Virtually every hand went up. Given the aforementioned statistics, this SHOCKED me.
There are two possibilities.
I’m sure it’s a combination of both in this case. Teachers tend to be fast learners. But it was such a pleasant surprise. They set a great example for everyone!
Static Maps in a Changing World
How could the flood maps during Harvey have been so far off? It was a combination of things.
Of course, Harvey was a far larger-than-normal storm – the biggest ever to hit the continental US.
Second, flood maps are a stationary snapshot in time. They assume nothing changes.
But we also know that things DO change:
The one thing that hasn’t changed: Montgomery County flood maps. The County has not updated the data behind them since the 1980s. Parts of the county remain unmapped. And the County does not even employ a surveyor, according to an inside source.
Radical Example of Impact of Upstream Development
Uncontrolled upstream development can totally change the game. Here’s a personal example.
Back in 1980, I bought a home on Spring Creek in the Dallas area. It was built two feet above the hundred year flood plain. The next year, developers built the 250-acre Collin Creek Mall upstream from me in Plano. The creek behind my house started flooding on minor rains of less than a half inch. A three city commission between Garland, Richardson and Plano asked the Army Corps to investigate.
That’s how radically and quickly things can change from upstream development as the people in Elm Grove discovered.
New Flood Maps Being Developed
NOAA’s new Atlas-14 Rainfall statistics for this area are causing flood maps to be redrawn. The statistics reflect about 40% more rain for a 100-year flood. That means flood zones will expand.
When released in the next year or two, the new maps will open a lot of eyes for people who have not yet purchased flood insurance.
Net: If you don’t have flood insurance, get it.
Another Type of Flood Insurance
That brings us to another type of flood insurance not covered by FEMA’s National Flood Insurance Program. It’s the kind of insurance that comes from situational awareness and community engagement.
The more aware we are of the causes of flooding…
The more engaged we are as citizens…
The more we insist that developers follow best practices…
…the safer we become.
We should not assume that some benevolent government agency in Montgomery County is watching over new development, protecting us. They are not. Period. They have other priorities and protecting downstream residents is rarely one of them. Even though Harris County is redrawing its flood maps, Montgomery County is not. That will make MoCo’s even MORE OUTDATED. That’s why we need vigilant, involved citizens.
Need Regional Flood Control
And even more, that’s why we need regional flood control, much as we have regional groundwater control. With groundwater withdrawals, one conservation district must get its plans approved by neighboring districts. Wouldn’t it be beautiful if we had a similar arrangement for flood control?
Posted by Bob Rehak on 2/11/2020
896 Days after 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.
Rain Forecast This Week
Jeff Lindner, Harris County Meteorologist but put this notice thus morning. He said wet weather will persist until mid week.
Slow-Moving Cold Front Stalls Out
A slow-moving cold front currently extends from Longview to north of Austin and is creeping southward. Ahead of this boundary a warm and moist air mass covers all of SE TX this morning. Meanwhile, north of the boundary a colder and somewhat drier air mass is in place.
Radar is fairly calm this morning with a couple of lines of showers lifting north over the region in the warm air advection pattern in place.
Surface cold front will move to near a Madisonville-to-College-Station line later this morning and then likely stall in that region today. Focus for rainfall today will be mainly across the northern half of the region closest to the front. Rainfall amounts today could average 1-2 inches north of HWY 105 as another upper level disturbance approaches from the WSW and interacts with the slow moving front.
Front Pushes South Tonight
Front will get another push this evening and likely progress southward toward the coast tonight. With the afternoon and evening short wave disturbance moving off to the ENE expect a lull in any heavier rains by late evening across the northern portions of the area.
Mainly light showers will impact the southern portions of the area this evening and overnight as the surface front stalls near the coast.
Tuesday Front Lifts Back North
On Tuesday the surface front begins lifting back northward as a warm front with a continued chance of showers over the area.
A strong upper level storm system currently digging into NW Mexico will begin to move slowly eastward and toward TX late Tuesday into Wednesday. This will result in the formation of a surface low pressure system over the coastal bend of TX Tuesday night which then moves ENE/NE across SE TX Wednesday.
Clearing Late in Week
This surface low will be strong enough to finally push a stronger front through the region and clear the area out for at least a couple of days before clouds and rain chances return for the weekend.
Yo-Yo Temperatures
Temperatures will be all over the place with the surface front stalling and then creeping across the area. Ahead of the front temperatures will be in the 70’s and then fall into the 60’s and possibly 50’s behind the boundary.
Rainfall 1-4 Inches, Highest to North
Rainfall Amounts:
Fairly tight rainfall gradient will setup across SE TX over the next 72 hours with much of the rainfall occurring north of HWY 105 and much lower amounts near the coast.
South of I-10 amounts of .50-1.0 inch will be possible. While the drought monitor shows dry conditions over much of the area, the time of year combined with lack of any vegetation growth and the widespread nature of the expected rains suggest rises on area creeks and rivers will be likely.
Currently predicted amounts are spread out enough to preclude any forecast to reach flood stage, but we will need to watch rainfall trends today and again on Tuesday especially north of HWY 105.
Should rainfall totals begin to pile up in our NE counties (Polk, Trinity, Houston, San Jacinto) a flash flood watch could be required for those areas.
Excessive Rainfall Outlook (Monday):
Excessive Rainfall Outlook (Tuesday):
Day 1-3 Forecast Rainfall Amounts:
Posted by Bob Rehak on 2/10/2020 with thanks to Jeff Lindner
895 Days since Hurricane Harvey
Construction Update: Perry Homes Adding Storm Sewers, Berm to Woodridge Village
Here’s a construction update for Perry Homes’ Woodridge Village, the stalled development implicated in flooding Elm Grove and North Kingwood Forest twice last year.
On January 25, 2020, I flew over Woodridge Village. Not much had changed since my December flyover. However, Perry Homes, had concreted about 280 feet of Taylor Gully on the east side of the development facing North Kingwood Forest. And they started to build a berm between Woodridge Village and Elm Grove. Finally, they have started prep work for building more streets. See images below.
Overview of Construction Activity
Slanting Berm Between Elm Grove and Woodridge
Since the January flyover, Perry Homes has continued to build up a berm south of the S2 detention pond. The height of the berm is about 3-4 feet immediately west of Taylor Gulley (grassy channel in lower right). It tapers down to nothing before you get to Fair Grove Drive, one long block to the west (out of frame to the left in picture above).
Whether Perry intends to build up the western portion of the berm is unclear. If they intend to go west beyond the point above and continue the berm south of the S1 pond, they have not yet done so.
The Strange Case of the Elevated Swale
Originally, I thought the berm might be the missing maintenance road that Montgomery County regulations specify around detention ponds. However, yesterday, Perry Homes’ contractor etched a ditch in the middle of the berm. I guess this ditch will act as the backslope interceptor swale, another requirement of detention ponds in Montgomery County.
Such swales channel water into ponds through pipes installed at low points. Their purpose: to prevent runoff from surrounding areas from flowing over the edge of ditches and causing erosion.
Except in this case, water from the surrounding areas would have to flow uphill several feet to get to the swale. So the swale will only channel water that falls directly on it.
No New Detention Ponds
No new detention ponds have been created since last August.
Prep Work for New Streets
However, Perry Homes is starting to add new storm drains to areas where roads have not yet reached on the north side of the S2 detention pond.
Perry Had Promised No New Streets Until All Detention Ponds In
Point #1 in Perry Homes’ letter to the City Attorney about remediation efforts promised that Perry would delay additional street construction until three detention ponds on the northern part of Woodridge Village were complete. But as you can see from the first photo above, no additional detention ponds have even been started on the northern portion of the site.
Possible Impact of Changes on Flooding
The concrete channel will reduce erosion, but will do nothing to reduce flooding. As you can see from the video below, taken by Jeff Miller after a minor rain, Perry Homes needs the three additional detention ponds they promised in 2017, two and a half years ago, to reduce flooding.
The berm may redirect flooding. The berm has the potential to change the location of flooding. As floodwaters build up in the S2 pond shown above, they will eventually rise above the overflow channel between the concrete portion of Taylor Gulley and the pond. When that happens, the water will go around the berm. It could happen on two sides. On the west at Fair Grove (above) and on the east at Taylor Gulley (below).
On the east side of the concrete portion of Taylor Gulley, notice how the edge slants down toward North Kingwood Forest (out of frame on the right).
Storm sewers, once connected to the detention ponds, will simply shorten the time of accumulation after heavy rains and fill the ponds even faster. That usually results in higher peaks. Again, without additional detention, there is no flood-reduction benefit for downstream residents.
Posted by Bob Rehak with help from Jeff Miller on 2/9/2020
894 Days after Hurricane Harvey and 143 after Imelda
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.