On the Harris County Commissioner’s Court agenda for today are two Harris County Flood Control District (HCFCD) “transmittals.” One will update commissioners on flood-bond spending to date. The other will update commissioners on the progress of new flood maps (the MAAPnext program). They are items 269 and 270 on today’s agenda.
Transmittals are reports by departments. Commissioners don’t usually discuss them unless one of the commissioners wishes to make comments for some reason. So, I’m calling them to your attention here.
Flood-Mitigation Spending Through Third Quarter Reaches $865 Million
About half of the $865 million spent on flood mitigation since voters passed the bond in 2018 has come from bond funds. The rest has come from grants and local partnerships. See pie chart below on left.
The left pie chart underscores the importance of partnership funding.
The map below shows where flood-bond spending has occurred.
Flood-mitigation spending by watershed since approval of flood-bond in 2018.
The winner in the $weep$take$: HCFCD spent almost $154 million on Brays Bayou.
Other leading watersheds (rounded to nearest million) in flood-bond spending included:
$81 million in Addicks Reservoir
$76 million on Greens Bayou
$76 million on Cypress Creek
$50 million on Little Cypress Creek
$46 million on White Oak Bayou
$32 million on Clear Creek
With a few exceptions, this spending reflects the influence of the Harris County Flood-Bond Equity Prioritization Framework implemented in 2019. That framework gives highest priority to low- to middle-income watersheds with a high social-vulnerability index. Thus, tiny Halls Bayou has received more assistance than the largest watershed in the county – the San Jacinto River. And Brays Bayou has received almost 11 times more assistance than Buffalo Bayou.
Two notable exceptions are:
Vince Bayou which is almost totally inside the City of Pasadena and is therefore primarily Pasadena’s responsibility.
Little Cypress Creek which is part of HCFCD’s experimental Frontier Program. The Frontier Program aims to prevent future flooding by buying up land on the cheap before it’s developed. HCFCD then sells detention basin capacity to developers to help make back its investment.
Other Insights Gained from Report
Most projects are ahead of schedule and on budget. Good news!
More than half of buyouts have been completed and enough funding apparently remains to complete the rest.
Progress continues on the $124 million FEDERAL Flood Damage Reduction project on White Oak Bayou, where six stormwater detention basins will hold almost a billion gallons of stormwater. That’s equivalent to about a foot of stormwater falling over almost 5 square miles.
An earlier version of this report generated some controversy. People in some watersheds didn’t believe the reported expenditures. Members of the Northeast Action Collective questioned whether any projects had started in their watersheds. They demanded immediate cancellation of projects in Kingwood and transfer of Kingwood’s funds, so that projects in Halls and Greens Bayou could start immediately.
That’s, in part, why I wrote “How to Find and Verify Flood-Related Information: Part I.” Flood-mitigation projects are hard to spot from the ground. Construction almost always happens out of sight behind tall fences and dense tree lines. After construction, the projects are often disguised as parks. For those who doubt, I recommend confirming the existence of projects from the air.
I haven’t confirmed every project in the county, but I have spot-checked many. And I have yet to find discrepancies between what HCFCD reports and what I can see from the air.
C-25, a Halls Bayou Detention pond now under construction by HCFCD. The bayou runs through the trees in the foreground.New basin at Hopper and US59 on a tributary of Halls Bayou.Lauder Detention Basin on Greens Bayou as of 10/12/2021. Phase One of a two-phase project is nearly complete.Cutten Road detention basin on Greens Bayou continues its relentless expansion.Phase 1 of the Greens Bayou Aldine-Westfield Basin on left is complete. Phase 2 on right is now beginning.
For more information that includes watershed spending data before the flood-bond, check out the funding page.
MAAPnext Effort About to Be Turned Over to FEMA
Harris County Flood Control (HCFCD) estimates it has completed 86% of its part of the flood-map updates. HCFCD will deliver drafts of the new maps to FEMA in January for review and kick off a campaign of public meetings at the same time. The public will see draft maps in February. A public comment period of 90 days will follow. And FEMA hopes to release preliminary flood insurance insurance rate maps by mid-year next year.
I have had a peek at the new maps and reports. And I must say, the effort should result in a dramatic leap forward in flood-risk understanding. Individualized reports will inform homeowners of their flood risks from a variety of different sources, including street flooding. The prototype of the website is very user friendly.
After receiving preliminary maps from HCFCD, it typically takes FEMA another 18-24 months to release final, official flood maps. That gives affected property owners time to comment and appeal. The process looks like this.
MAAPnext milestones as of the end of 2021.
Posted by Bob Rehak on 11/30/2021
1554 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2021/11/20211130-Screen-Shot-2021-11-30-at-10.31.04-AM-2.jpg?fit=1200%2C836&ssl=18361200adminadmin2021-11-30 12:47:472021-11-30 12:47:51Where Flood-Bond Spending Is Going, When New Flood Maps Will Be Released
This is Part II in a series about how to find and verify flood-related information. Yesterday’s post focused on finding good information about flood vulnerabilities. This second part will focus on reviewing developers’ plans. The second can compound the first.
The very first sentence of the Texas Water Code § 11.086 begins with a warning not to flood your neighbors. It says, “No person may divert or impound the natural flow of surface waters in this state, or permit a diversion or impounding by him to continue, in a manner that damages the property of another by the overflow of the water diverted or impounded.”
The second sentence declares that a person injured by diverted water may sue to recover damages. Of course, at that point the damage has already been done. Lawsuits are expensive and take years. And the defendant, usually a developer, will always point to plans prepared by a professional engineer and approved by a government body. Suing them will require expert witnesses. And the defendant will likely claim that you wouldn’t have flooded except for an Act of God.
Lawsuits are tall, expensive mountains to climb. So concerned residents near new developments are better off closely scrutinizing plans before they’re built and closely monitoring construction to ensure developers follow the plans.
You can’t stop development. But you can ensure developers play by the rules.
But how do you find and verify their plans?
Need to Find and Verify Info
If you notice a large piece of property for sale near you, monitor it closely. Check with the listing agent. Also check Houston’s Plat Tracker website. It’s updated before every meeting of the Planning Commission and shows items on their agenda. Houston also maintains a map-based website that shows projects in various stages of approval throughout the City and its extra-territorial jurisdiction.
Leap into action if you find a potential cause for concern near you. The next step is to obtain the development’s plans, the drainage impact analysis and soil tests. The developer must prove “no adverse impact” to people and properties downstream.
How you obtain those plans and studies depends on the development’s location. If inside a municipality, check with your city council representative. If you live outside a municipality, your best starting point will probably be your county engineer or precinct commissioner.
The plans are public information and must be provided in response to Freedom of Information Act (FOIA) Requests.
Signed, Stamped, Approved and So Obviously Wrong
In every case I reviewed during the last four years where someone flooded because of a new development, something jumped out of the plans that should have raised concerns for reviewers, but didn’t.
For instance, after Colony Ridge engineers apparently mischaracterized soil types, Plum Grove flooded repeatedly. The engineer said soils would let more water soak in than actually could. That meant the developer didn’t have to build as many detention ponds and could sell more lots. But it also contributed to flooding homes downstream.
Concerned citizens must learn how to obtain and review such plans for potential problems or hire a consulting engineer.
Here are some things I’ve learned to look for.
Soil Tests
Are they accurate? Were the samples taken at representative points? Or did they conveniently ignore wetlands? Permeability of the soils will affect the amount of detention needed. The level of the water table could affect the amount of detention provided.
If plans call for a ten-foot deep detention pond, but the soil test encounters a shallower water table, that will compromise the pond’s capacity. Capacity should be calculated from the top of standing water, not the bottom of the pond. If the pond is already half full, that half shouldn’t count.
Floodplain maps in Harris County are currently being revised. That may not be the case in surrounding counties. The lack of updated flood maps endangers current residents, by letting developers build to old and ineffective standards.
Developers often try to beat the implementation of new requirements. This happened in the case of Woodridge Village. It’s also happening in the case of the Laurel Springs RV Park and Northpark South along Sorters-McClellan Road. The entrance to the Northpark development sits in a bowl. A quick check of the elevation profile on the USGS National Map confirmed that. During Harvey, local residents tell me that not even high-water rescue vehicles could get through that intersection. Put the Cajun Navy on standby now.
Wetland Issues
Filling wetlands requires an Army Corps permit for some, but not all wetlands. Whether they fall under the Corps’ jurisdiction depends on how far up in the branching structure of a watershed they are. Those near the main stem are jurisdictional. Three levels up may not be.
The US Fish and Wildlife service has thoroughly documented wetlands in this area. Check their National Wetlands Database and appeal to the Corps if you find a problem. At a minimum, the developer may be forced to buy mitigation credits somewhere nearby, which could help reduce flooding.
Drainage Issues
Is a new development’s detention pond capacity adequate? Is it based on the right percentage of impermeable cover? If the pond(s) fill up, where will the water go?
Calculating detention capacity requires math skills most people don’t have. But you can check the basis for the calculations. Are plans based on new Atlas-14 requirements? Are plans meeting current Houston and Harris County requirements?
Current City of Houston and Harris County Requirements for Detention Pond Capacity
Also see where they’re routing excess water in case of an overflow.
In the case of the Laurel Springs RV Park, the developer said they would route the water to a detention pond near Hamblen and Laurel Springs in anything greater than a two year rain. See below.
Screen Capture from Laurel Springs RV Resort Drainage Impact Report shows that in anything greater than a 2-year rain, overflow water will could threaten homes in Lakewood Cove.
RV Park Site Outlined in White. Overflow described above would presumably follow red path.
Laurel Springs RV Park as of 11/29/21. Detention pond will go in foreground, but overflow will go into pond at top of frame according to text above.
Missing Details from Drainage Impact Analysis
I have requested additional details three times from the City but still have not received them. I suspect they may not exist. All other plan requests have been filled.
So what happens when the Lakewood Cove detention pond fills up? Or gets covered up in a flood? Overflow from the RV park will contribute to flooding someone downstream.
The developer also said excess capacity would get to the Lakewood Cove pond by overland sheet flow. That could threaten homes on the southwest corner of Lakewood Cove – visible in the middle of shot above.
But a City engineer reviewing the plans said overflow would follow the railroad tracks on the western side of the RV park. Hmmmm. Two engineers – one who developed the plans and another who approved them – 180 degrees apart. What’s a concerned citizen to do?
If the engineers who develop and review such plans were always right, no one would ever flood. But we do. So always find and verify those plans.
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/2021/11/20211129-DJI_0877-2.jpg?fit=1200%2C799&ssl=17991200adminadmin2021-11-29 19:09:202021-12-08 15:51:19How to Find and Verify Flood-Related Information: Part II
This will be the first of a two-part series on how to find and verify flood-related information. Today’s post will focus on flooding itself. Tomorrow’s will focus on how some developers can affect flooding. Together, they should help you protect yourself whether you are a homebuyer, homeowner, or community activist.
Triangulating on Truth
The world is awash in misinformation. Most of it results from people simply repeating things they’ve heard but haven’t verified. And some of it is intentional, i.e., for political or financial gain.
Getting an accurate picture of the world around you often involves investigation and “triangulating on truth” by looking at multiple perspectives.
Below are sources of information you may find useful. They represent my go-to sources. I often supplement them with interviews, but I usually start with these.
The Harris County Flood Control District’s website, HCFCD.org, is a wealth of information about what’s happening where. It is organized by watershed. Click one to see an overview of issues there, flood mitigation projects that address them, maps, risks, costs, pending grants, and more. Note: Flood Control manages hundreds of projects. Sometimes the projects move faster than website updates. So it’s always good to verify the status of projects by laying eyes on them.
The Harris County Flood Warning System, HarrisCountyFWS.org, gives you real-time information during floods. It also gives you historical information about rainfall, gage heights, and flooding at locations throughout the region. You can use this site to explore when, if, or how often a channel came out of its banks and by how much.
Note: Before 2010 you may find suspicious data because of the type of gages in use during that period. Pressure transducers frequently clogged with floating debris and reported false information. So, if you see a hundred-foot flood that lasted 15 minutes, you’re likely looking at error. Cross check the reading against rainfall at the same gage. Also check the readings immediately up and downstream.
Using this information, you can help narrow down the source of flooding. If a neighborhood flooded, but the channel didn’t come out of its banks, chances are that you’re looking at a street flooding issue. Most storm sewers and roadside ditches in Harris County and Houston are sized to handle a two-year rain. But older ones may have only a one-year level of service. And many become clogged over time. See below.
Drive Around and Talk to Residents
To confirm whether street flooding is your issue, drive around and look at the ditches and storm drains. Even if you clean out your ditch but a neighbor doesn’t, water could be trapped in your neighborhood. The photo below shows ditches in three areas that report frequent flooding: Kashmere Gardens, Trinity Gardens, and East Aldine. They are symbolic of a problem that exists in many other areas..
Ditches blocked by silt in Kashmere Gardens, Trinity Gardens, and East Aldine
Report blocked drains and ditches to authorities. Who you report them to will depend on where you live. Inside the City of Houston or another municipality, report them to the city. If you live outside a city but inside Harris County, report them to your precinct commissioner. The Harris County Flood Control District is not involved in roadside ditches. Flood Control only works on channels, bayous and rivers.
Ditch blocked by garbage in Kashmere Gardens, a neighborhood that experiences frequent flooding.
Drones/Helicopters
It’s often hard to see Flood Control projects from the ground. Construction happens behind tall fences and trees in remote areas. However, you can spot projects easily from the air with drones or helicopters.
Phase 1 of the new Lauder Detention Basin on Greens Bayou is virtually invisible from streets. Yet many Greens Bayou residents are convinced nothing is being done to protect them.
The Harris County Flood Education Mapping Tool at HarrisCountyFEMT.org was developed after Tropical Storm Allison in 2001. It shows channels and watershed boundaries. Zoom in to find your neighborhood. That activates the ponding button. You can then see areas likely to flood from ponding or, alternatively, floodplains. Note: Most of the current flood maps for Harris County are based on Allison but are now being updated.
This particular tool is geared toward coastal areas but also covers all of Harris County. It includes FEMA’s flood hazard layers (see below), plus dozens of other visualization tools, all in one website. It shows development density, wetlands, emergency infrastructure, and much, much more. The site also lets you vary opacity of different layers and save maps.
A one-stop shop for flood preparedness anywhere in Texas. TexasFlood.org brings together local information from all over the state. Check everything from stream gages to the status of evacuation routes. It even lets you see the spread of floodwaters and the structures that will be inundated when a gage reaches a certain height. Hosted by the Texas Water Development Board.
Not exactly a flood map, Texas Watershed Viewer is useful in figuring out where water comes from and how it converges. This also lets you see how streams may have been altered. For instance, a part of North Kingwood Forest that used to drain into Mills Branch now drains into Taylor Gully where hundreds of homes flooded in 2019.
A Texas Water Development Board/USGS site. Click on a river gage, select a flood depth, and see how far the waters would spread. Clicking on a location within the flooded area will also show you the estimated depth at that point. You can also turn on a layer that shows flooded buildings. Unfortunately, however, the number of gages is limited, and most are in northern Harris and southern Montgomery Counties.
FEMA’s National Flood Hazard Layer Viewer lets you zoom into any part of the country. Wait a few seconds. And outlines for the floodway, 100-year flood plain and 500-year floodplains will appear. This website has amazing investigative potential. With it, you can tell how far your home or business is from flood threats.
FEMA’s Flood Map Service Center lets you plug in any address and instantly see where your property stands in relation to floodplains that may exist around it.
The USGS National Map Viewer lets you find elevations and slopes everywhere in the US and works down to the individual property level. Find the elevation of your slab, the slope of your street, your elevation above street level, and more. Best of its kind. Here’s a post that explains more about how to use it. Realtors and people who want to buy homes with minimal flood risk will find this useful.
Want to know if a house was built on wetlands? Check the US Fish and Wildlife Service Wetlands Mapper. Some developers fill in wetlands to build more homes. But those homes are subject to foundation shifting and driveway cracking. Also, water will often collect in former wetlands after a storm. See below. Also note how the homes are built within feet of a major ditch. These factors should send signals to homebuyers, who may want to request discounts to compensate for increased risk.
High-density neighborhood built over wetlands near East Little York
Enter your address or zip code in NOAA’s Precipitation Data Frequency Server and see the Atlas-14 precipitation frequency estimates for your neighborhood, in graphical or tabular formats. This will tell you what constitutes a 1-, 2-, 5-, 10-, 25-, 50-, 100-, 200-, 500-, or 1000-year rain in your area. The rates vary with distance from the coast.
Precipitation Frequency Estimates for 77339. 17.3 inches in 24 hours constitutes a 100-year rain. You can see how storm sewers designed to hold a 1-year rain could easily become overwhelmed in a climate like Houston’s.
If your neighborhood floods on less than the 1- to 2-year amounts shown above, you may need to investigate the cause.
Imelda left a 13-foot high bathtub ring around around East End Park in Kingwood.With this knowledge and the elevation of a home’s slab from a survey or the USGS National Map, you could determine whether a particular home flooded during Imelda.
Other Valuable Sources for Flood-Related Information
Google Earth Pro
Using the History Function in Google Earth Pro (a Free App Download) lets you scroll back through aerial and satellite images of an area at different points in time. With it, you can see how neighborhoods filled in floodplains, rivers migrated, deltas formed, and more. The app also contains powerful measurement tools to calculate area and distance. Using this gives you a greater appreciation for the difficulty of building flood mitigation projects where people build too close to bayous, ditches, and rivers. Whole neighborhoods must be bought out before construction can begin. Check out, for instance, the detention ponds on both sides of US59 at Halls Bayou.
All people are entitled to request government information under the Freedom of Information Act or Texas Public Information Act. Both are valuable tools for getting at information that may not be published. Make sure you put FOIA or TPIA in the subject line of your email and state your request as succinctly as possible. Certain records are exempt (such as personnel files and correspondence with lawyers). But bids, plans, reports, and spending information are all fair requests. Generally, a government agency has 10 business days to respond. Different agencies have different procedures and starting points. So you may want to call or google before submitting your request.
Caveat Emptor
Buyer Beware. The ancient slogan applies to flood-related information as well as homes. The more you know, the safer you are.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/06/NOAA-Atlas-14-Rainfall-Rates-for-Kingwood.png?fit=976%2C828&ssl=1828976adminadmin2021-11-28 17:11:042021-11-30 12:58:53How to Find and Verify Flood-Related Information
Where Flood-Bond Spending Is Going, When New Flood Maps Will Be Released
On the Harris County Commissioner’s Court agenda for today are two Harris County Flood Control District (HCFCD) “transmittals.” One will update commissioners on flood-bond spending to date. The other will update commissioners on the progress of new flood maps (the MAAPnext program). They are items 269 and 270 on today’s agenda.
Transmittals are reports by departments. Commissioners don’t usually discuss them unless one of the commissioners wishes to make comments for some reason. So, I’m calling them to your attention here.
Flood-Mitigation Spending Through Third Quarter Reaches $865 Million
About half of the $865 million spent on flood mitigation since voters passed the bond in 2018 has come from bond funds. The rest has come from grants and local partnerships. See pie chart below on left.
The map below shows where flood-bond spending has occurred.
Other leading watersheds (rounded to nearest million) in flood-bond spending included:
With a few exceptions, this spending reflects the influence of the Harris County Flood-Bond Equity Prioritization Framework implemented in 2019. That framework gives highest priority to low- to middle-income watersheds with a high social-vulnerability index. Thus, tiny Halls Bayou has received more assistance than the largest watershed in the county – the San Jacinto River. And Brays Bayou has received almost 11 times more assistance than Buffalo Bayou.
Two notable exceptions are:
Other Insights Gained from Report
Additional maps in the full report show:
Also, a massive GANNT chart shows the stages of every project in every watershed and county-wide projects.
Check out the full report here.
Controversy over Previous Version of Report
An earlier version of this report generated some controversy. People in some watersheds didn’t believe the reported expenditures. Members of the Northeast Action Collective questioned whether any projects had started in their watersheds. They demanded immediate cancellation of projects in Kingwood and transfer of Kingwood’s funds, so that projects in Halls and Greens Bayou could start immediately.
That’s, in part, why I wrote “How to Find and Verify Flood-Related Information: Part I.” Flood-mitigation projects are hard to spot from the ground. Construction almost always happens out of sight behind tall fences and dense tree lines. After construction, the projects are often disguised as parks. For those who doubt, I recommend confirming the existence of projects from the air.
I haven’t confirmed every project in the county, but I have spot-checked many. And I have yet to find discrepancies between what HCFCD reports and what I can see from the air.
For more information that includes watershed spending data before the flood-bond, check out the funding page.
MAAPnext Effort About to Be Turned Over to FEMA
Harris County Flood Control (HCFCD) estimates it has completed 86% of its part of the flood-map updates. HCFCD will deliver drafts of the new maps to FEMA in January for review and kick off a campaign of public meetings at the same time. The public will see draft maps in February. A public comment period of 90 days will follow. And FEMA hopes to release preliminary flood insurance insurance rate maps by mid-year next year.
I have had a peek at the new maps and reports. And I must say, the effort should result in a dramatic leap forward in flood-risk understanding. Individualized reports will inform homeowners of their flood risks from a variety of different sources, including street flooding. The prototype of the website is very user friendly.
After receiving preliminary maps from HCFCD, it typically takes FEMA another 18-24 months to release final, official flood maps. That gives affected property owners time to comment and appeal. The process looks like this.
Posted by Bob Rehak on 11/30/2021
1554 Days since Hurricane Harvey
How to Find and Verify Flood-Related Information: Part II
This is Part II in a series about how to find and verify flood-related information. Yesterday’s post focused on finding good information about flood vulnerabilities. This second part will focus on reviewing developers’ plans. The second can compound the first.
The very first sentence of the Texas Water Code § 11.086 begins with a warning not to flood your neighbors. It says, “No person may divert or impound the natural flow of surface waters in this state, or permit a diversion or impounding by him to continue, in a manner that damages the property of another by the overflow of the water diverted or impounded.”
The second sentence declares that a person injured by diverted water may sue to recover damages. Of course, at that point the damage has already been done. Lawsuits are expensive and take years. And the defendant, usually a developer, will always point to plans prepared by a professional engineer and approved by a government body. Suing them will require expert witnesses. And the defendant will likely claim that you wouldn’t have flooded except for an Act of God.
Lawsuits are tall, expensive mountains to climb. So concerned residents near new developments are better off closely scrutinizing plans before they’re built and closely monitoring construction to ensure developers follow the plans.
But how do you find and verify their plans?
Need to Find and Verify Info
If you notice a large piece of property for sale near you, monitor it closely. Check with the listing agent. Also check Houston’s Plat Tracker website. It’s updated before every meeting of the Planning Commission and shows items on their agenda. Houston also maintains a map-based website that shows projects in various stages of approval throughout the City and its extra-territorial jurisdiction.
Leap into action if you find a potential cause for concern near you. The next step is to obtain the development’s plans, the drainage impact analysis and soil tests. The developer must prove “no adverse impact” to people and properties downstream.
How you obtain those plans and studies depends on the development’s location. If inside a municipality, check with your city council representative. If you live outside a municipality, your best starting point will probably be your county engineer or precinct commissioner.
The plans are public information and must be provided in response to Freedom of Information Act (FOIA) Requests.
Signed, Stamped, Approved and So Obviously Wrong
In every case I reviewed during the last four years where someone flooded because of a new development, something jumped out of the plans that should have raised concerns for reviewers, but didn’t.
For instance, after Colony Ridge engineers apparently mischaracterized soil types, Plum Grove flooded repeatedly. The engineer said soils would let more water soak in than actually could. That meant the developer didn’t have to build as many detention ponds and could sell more lots. But it also contributed to flooding homes downstream.
Another example, the engineers for Woodridge Village claimed there were no floodplains on the property when there were. The property just hadn’t been surveyed yet.
In those cases, multiple other issues surfaced after close review. Wetlands that had been ignored. Substandard construction of detention ditches that led to severe erosion. Failure to implement stormwater quality controls. Failure to follow plans. Ignoring Atlas-14 requirements that led to undersizing detention ponds by 40%. And more.
In another development, I spotted safety issues related to river migration that had been ignored. Underground parking next to the floodway of the San Jacinto River. Failure to consider flood evacuation.
Concerned citizens must learn how to obtain and review such plans for potential problems or hire a consulting engineer.
Here are some things I’ve learned to look for.
Soil Tests
Are they accurate? Were the samples taken at representative points? Or did they conveniently ignore wetlands? Permeability of the soils will affect the amount of detention needed. The level of the water table could affect the amount of detention provided.
You can check the soils that a developer reports against the USDA national soil database.
Floodplain Issues
Floodplain maps in Harris County are currently being revised. That may not be the case in surrounding counties. The lack of updated flood maps endangers current residents, by letting developers build to old and ineffective standards.
Developers often try to beat the implementation of new requirements. This happened in the case of Woodridge Village. It’s also happening in the case of the Laurel Springs RV Park and Northpark South along Sorters-McClellan Road. The entrance to the Northpark development sits in a bowl. A quick check of the elevation profile on the USGS National Map confirmed that. During Harvey, local residents tell me that not even high-water rescue vehicles could get through that intersection. Put the Cajun Navy on standby now.
Wetland Issues
Filling wetlands requires an Army Corps permit for some, but not all wetlands. Whether they fall under the Corps’ jurisdiction depends on how far up in the branching structure of a watershed they are. Those near the main stem are jurisdictional. Three levels up may not be.
The US Fish and Wildlife service has thoroughly documented wetlands in this area. Check their National Wetlands Database and appeal to the Corps if you find a problem. At a minimum, the developer may be forced to buy mitigation credits somewhere nearby, which could help reduce flooding.
Drainage Issues
Is a new development’s detention pond capacity adequate? Is it based on the right percentage of impermeable cover? If the pond(s) fill up, where will the water go?
Calculating detention capacity requires math skills most people don’t have. But you can check the basis for the calculations. Are plans based on new Atlas-14 requirements? Are plans meeting current Houston and Harris County requirements?
In the case of the RV park, the developer will provide roughly half the current capacity requirement thanks to a grandfather clause in the regs. You can find construction guidelines for Houston, Harris County, MoCo and Liberty County on the Reports Page under the Construction tab.
Also see where they’re routing excess water in case of an overflow.
In the case of the Laurel Springs RV Park, the developer said they would route the water to a detention pond near Hamblen and Laurel Springs in anything greater than a two year rain. See below.
Missing Details from Drainage Impact Analysis
I have requested additional details three times from the City but still have not received them. I suspect they may not exist. All other plan requests have been filled.
So what happens when the Lakewood Cove detention pond fills up? Or gets covered up in a flood? Overflow from the RV park will contribute to flooding someone downstream.
The developer also said excess capacity would get to the Lakewood Cove pond by overland sheet flow. That could threaten homes on the southwest corner of Lakewood Cove – visible in the middle of shot above.
But a City engineer reviewing the plans said overflow would follow the railroad tracks on the western side of the RV park. Hmmmm. Two engineers – one who developed the plans and another who approved them – 180 degrees apart. What’s a concerned citizen to do?
If the engineers who develop and review such plans were always right, no one would ever flood. But we do. So always find and verify those plans.
To see the first part of this series, click here.
Posted by Bob Rehak on 11/29/2021
1553 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.
How to Find and Verify Flood-Related Information
This will be the first of a two-part series on how to find and verify flood-related information. Today’s post will focus on flooding itself. Tomorrow’s will focus on how some developers can affect flooding. Together, they should help you protect yourself whether you are a homebuyer, homeowner, or community activist.
Triangulating on Truth
The world is awash in misinformation. Most of it results from people simply repeating things they’ve heard but haven’t verified. And some of it is intentional, i.e., for political or financial gain.
Getting an accurate picture of the world around you often involves investigation and “triangulating on truth” by looking at multiple perspectives.
Below are sources of information you may find useful. They represent my go-to sources. I often supplement them with interviews, but I usually start with these.
Local Sources
HCFCD.org
The Harris County Flood Control District’s website, HCFCD.org, is a wealth of information about what’s happening where. It is organized by watershed. Click one to see an overview of issues there, flood mitigation projects that address them, maps, risks, costs, pending grants, and more. Note: Flood Control manages hundreds of projects. Sometimes the projects move faster than website updates. So it’s always good to verify the status of projects by laying eyes on them.
HarrisCountyFWS.org
The Harris County Flood Warning System, HarrisCountyFWS.org, gives you real-time information during floods. It also gives you historical information about rainfall, gage heights, and flooding at locations throughout the region. You can use this site to explore when, if, or how often a channel came out of its banks and by how much.
Note: Before 2010 you may find suspicious data because of the type of gages in use during that period. Pressure transducers frequently clogged with floating debris and reported false information. So, if you see a hundred-foot flood that lasted 15 minutes, you’re likely looking at error. Cross check the reading against rainfall at the same gage. Also check the readings immediately up and downstream.
Using this information, you can help narrow down the source of flooding. If a neighborhood flooded, but the channel didn’t come out of its banks, chances are that you’re looking at a street flooding issue. Most storm sewers and roadside ditches in Harris County and Houston are sized to handle a two-year rain. But older ones may have only a one-year level of service. And many become clogged over time. See below.
Drive Around and Talk to Residents
To confirm whether street flooding is your issue, drive around and look at the ditches and storm drains. Even if you clean out your ditch but a neighbor doesn’t, water could be trapped in your neighborhood. The photo below shows ditches in three areas that report frequent flooding: Kashmere Gardens, Trinity Gardens, and East Aldine. They are symbolic of a problem that exists in many other areas..
Report blocked drains and ditches to authorities. Who you report them to will depend on where you live. Inside the City of Houston or another municipality, report them to the city. If you live outside a city but inside Harris County, report them to your precinct commissioner. The Harris County Flood Control District is not involved in roadside ditches. Flood Control only works on channels, bayous and rivers.
Drones/Helicopters
It’s often hard to see Flood Control projects from the ground. Construction happens behind tall fences and trees in remote areas. However, you can spot projects easily from the air with drones or helicopters.
HarrisCountyFEMT.org
The Harris County Flood Education Mapping Tool at HarrisCountyFEMT.org was developed after Tropical Storm Allison in 2001. It shows channels and watershed boundaries. Zoom in to find your neighborhood. That activates the ponding button. You can then see areas likely to flood from ponding or, alternatively, floodplains. Note: Most of the current flood maps for Harris County are based on Allison but are now being updated.
Coastal Flood Exposure Mapper
This particular tool is geared toward coastal areas but also covers all of Harris County. It includes FEMA’s flood hazard layers (see below), plus dozens of other visualization tools, all in one website. It shows development density, wetlands, emergency infrastructure, and much, much more. The site also lets you vary opacity of different layers and save maps.
City of Houston Water Flood Hazards
City of Houston maintains a GIS site that shows the extent of flood hazards for many smaller streams and ditches in neighborhoods that are not covered in county or national maps.
Texas Sources of Flood-Related Information
TexasFlood.org
A one-stop shop for flood preparedness anywhere in Texas. TexasFlood.org brings together local information from all over the state. Check everything from stream gages to the status of evacuation routes. It even lets you see the spread of floodwaters and the structures that will be inundated when a gage reaches a certain height. Hosted by the Texas Water Development Board.
Texas Flood Viewer
Texas Flood Viewer shows gages throughout Texas. Click on a dot and you can see current water level relative to various flood stages.
Texas Watershed Viewer
Not exactly a flood map, Texas Watershed Viewer is useful in figuring out where water comes from and how it converges. This also lets you see how streams may have been altered. For instance, a part of North Kingwood Forest that used to drain into Mills Branch now drains into Taylor Gully where hundreds of homes flooded in 2019.
Flood Decision Support Toolbox
A Texas Water Development Board/USGS site. Click on a river gage, select a flood depth, and see how far the waters would spread. Clicking on a location within the flooded area will also show you the estimated depth at that point. You can also turn on a layer that shows flooded buildings. Unfortunately, however, the number of gages is limited, and most are in northern Harris and southern Montgomery Counties.
National Sources of Flood-Related Information
FEMA Estimated Base Flood Elevation Viewer
This site shows not only the extent but also the estimated depth of floods. It maps many areas not included in the National Flood Hazard Layer Viewer. See below.
FEMA National Flood Hazard Layer Viewer
FEMA’s National Flood Hazard Layer Viewer lets you zoom into any part of the country. Wait a few seconds. And outlines for the floodway, 100-year flood plain and 500-year floodplains will appear. This website has amazing investigative potential. With it, you can tell how far your home or business is from flood threats.
FEMA Flood Map Service Center
FEMA’s Flood Map Service Center lets you plug in any address and instantly see where your property stands in relation to floodplains that may exist around it.
USGS National Map Viewer
The USGS National Map Viewer lets you find elevations and slopes everywhere in the US and works down to the individual property level. Find the elevation of your slab, the slope of your street, your elevation above street level, and more. Best of its kind. Here’s a post that explains more about how to use it. Realtors and people who want to buy homes with minimal flood risk will find this useful.
US Fish and Wildlife Service Wetlands Mapper
Want to know if a house was built on wetlands? Check the US Fish and Wildlife Service Wetlands Mapper. Some developers fill in wetlands to build more homes. But those homes are subject to foundation shifting and driveway cracking. Also, water will often collect in former wetlands after a storm. See below. Also note how the homes are built within feet of a major ditch. These factors should send signals to homebuyers, who may want to request discounts to compensate for increased risk.
NOAA’s Precipitation Data Frequency Server
Enter your address or zip code in NOAA’s Precipitation Data Frequency Server and see the Atlas-14 precipitation frequency estimates for your neighborhood, in graphical or tabular formats. This will tell you what constitutes a 1-, 2-, 5-, 10-, 25-, 50-, 100-, 200-, 500-, or 1000-year rain in your area. The rates vary with distance from the coast.
If your neighborhood floods on less than the 1- to 2-year amounts shown above, you may need to investigate the cause.
USGS High-Water Marks
High water marks validate the extent of flooding. After Harvey, the US Geological Survey measured them at 74 selected points throughout SE Texas and published them in this study. Check out this event viewer to learn about other floods and how they affected various neighborhoods or this post to learn how high-water marks fill gaps in flood-related information.
Other Valuable Sources for Flood-Related Information
Google Earth Pro
Using the History Function in Google Earth Pro (a Free App Download) lets you scroll back through aerial and satellite images of an area at different points in time. With it, you can see how neighborhoods filled in floodplains, rivers migrated, deltas formed, and more. The app also contains powerful measurement tools to calculate area and distance. Using this gives you a greater appreciation for the difficulty of building flood mitigation projects where people build too close to bayous, ditches, and rivers. Whole neighborhoods must be bought out before construction can begin. Check out, for instance, the detention ponds on both sides of US59 at Halls Bayou.
FOIA and TPIA Requests
All people are entitled to request government information under the Freedom of Information Act or Texas Public Information Act. Both are valuable tools for getting at information that may not be published. Make sure you put FOIA or TPIA in the subject line of your email and state your request as succinctly as possible. Certain records are exempt (such as personnel files and correspondence with lawyers). But bids, plans, reports, and spending information are all fair requests. Generally, a government agency has 10 business days to respond. Different agencies have different procedures and starting points. So you may want to call or google before submitting your request.
Caveat Emptor
Buyer Beware. The ancient slogan applies to flood-related information as well as homes. The more you know, the safer you are.
To see the second part of this series which focuses on developers’ plans, click here.
Posted by Bob Rehak on 11/28/21
1552 Days since Hurricane Harvey