A study by Samuel D. Brody, Sammy Zahran, Wesley E. Highfield, Himanshu Grover, and Arnold Vedlitz called “Identifying the impact of the built environment on flood damage in Texas” quantifies the flood reduction benefits of wetlands along the Gulf coast. The authors studied property damage in 423 floods between 1997 and 2001. They identified the effect of several built-environment issues, including wetland alteration, impervious surface and dams on reported property damage while controlling for biophysical and socio-economic characteristics.
Their statistical results suggest that naturally occurring wetlands play a particularly important role in mitigating flood damage. But how much? The results vary by location, of course, but in one county, they discovered that a 3.4X increase in wetland alteration permits correlated to a 10X increase in flood damage.
Floods damage more property than any other type of natural disaster in America – billions of dollars every year. However, the author’s say, there is lack of research on the relationship between the built environment and flood impacts in the eastern portion of Texas. Say the authors, “Such information is critical given the continued development of coastal areas and the increasing vulnerability of human populations to inland coastal flooding.”
What Study Correlated and How
The authors correlated flood property damage (total dollar loss adjusted by the consumer price index) to variables such as:
Precipitation (day of flood)
Precipitation (day before flood)
Percentage of county in 100-year floodplains
Duration of flood
Dams
Percent impervious surface
Wetland alteration
FEMA Community Rating System
Median Household Income
They measured everything by counties. Watershed data would have been better for floods, but damage is not often aggregated by watersheds.
Researchers measured “wetland alterations” by counting wetland permits issued by the US Army Corps of Engineers in Galveston under Section 404 of the Clean Water Act. They simply counted the number of permits issued up to the day of any given flood. This enabled them to measure the cumulative impact of wetland alterations over time.
FEMA’s Community Rating System encourages city and county leaders to promote responsible development over time. The more an area reduces flood damage through regulations, mapping and 18 flood mitigation measures, the higher the discounts that residents earn on flood insurance.
The researchers used multivariate regression analyses to find which factors most influenced the degree of flood damage in eastern Texas. Multivariate regression identifies the degree of influence that multiple variables have over each other. It measures correlation, not causation.
Major Findings
Specific characteristics of the human-built environment in eastern Texas have an important influence on property damage resulting from floods, even when controlling for biophysical and socio-economic factors. Below are four major findings from the study.
First. the amount and duration of precipitation associated with a given storm flood largely governs flood damage.
When looking at biophysical variables, timing of precipitation is particularly important. “Heavy precipitation the day before the actual flood event is by far the strongest predictor of total property damage,” say the authors. This may be because of the delay in the rise of water or the saturation of soil. “It is important for decision-makers and the public to understand that heavy precipitation followed by sunny skies can still result in significant flood damage the next day.”
Second, the most important built-environment indicator of flood damage is the the alteration of naturally occurring wetlands.
“Impervious surfaces have long been criticised for their contribution to increased flooding and associated damage. However, the most significant impact may not depend solely on the total amount of imperviousness in a watershed or drainage basin, but rather on where exactly these built surfaces are placed. Altering or removing a wetland to construct car parks, roads and rooftops, for instance, effectively eliminates its ability to capture, hold and store water run-off.”
For example, comparing two identical rainfalls four years apart in De Witt County showed a 10X increase in damage. During that time, the number of wetland permits granted increased from 5 to 17 – 3.4X.
Similarly, comparing two 1.5 inch rainfalls in Wharton County, damage doubled while the number of wetland-alteration permits increased from 17 to 26.
Incredibly, Galveston County experienced a 20X increase in flood damage based on two 0.09 inch rainfalls three years apart. During that time, the number of wetland permits increased from 546 to 921.
“Developments initially believed to be safe from flood threats become an unexpected target of expensive flood damage over time,” say the authors. “The planning goal in this situation is to allow development to proceed without reducing the hydrological function and value of wetland systems.”
The authors suggest that achieving this objective will involve identifying and protecting wetlands through local land use policies. They include zoning restrictions, land acquisition programs, clustered development, density bonuses and more. Net economic benefits to a locality may result by reducing costs related to repair of damaged structures and mitigation solutions.
Third, wetlands may be more effective than dams in mitigating property loss over time.
Dams are extremely costly mitigation alternatives. And they can encourage development in flood-prone areas out of a false sense of security. See more below.
Fourth, FEMA’s Community Rating System reduces property damage.
Communities ranked high by FEMA for mitigation measures experience significantly lower amounts of flood-related property damage. “In fact, CRS participation appears to reduce community-wide flood damage more than dams, which are far more costly,” the study claims.
Economic Tradeoffs
In comparing the relative effects of various variables on flood damage, the authors also assessed economic tradeoffs of various mitigation measures.
For instance, they compared the cost in property damage in a flood to the price of wetland permits and dams. They found that 129 wetland alteration permits cost as much property damage per flood as one dam saved.
“Given the expense of building dams, their negative environmental ramifications, and the possibility of structural failure, protecting naturally occurring wetlands may be a more rational policy alternative,” says the study.
Posted by Bob Rehak on 1/30/21 based on a study by Samuel Brody, et. al.
1250 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/11/SJR_704_048-e1612057029212.jpg?fit=1200%2C811&ssl=18111200adminadmin2021-01-30 19:57:462021-02-01 15:54:48Scientists Quantify Flood-Damage-Reduction Benefit of Texas Wetlands
Texans for Responsible Aggregate Mining (TRAM) released a new video today demonstrating statewide issues with aggregate production operators (APOs). Just in time for the 2021 legislative session, the 12-minute video calls the concerns non-partisan, but says they requiring bi-partisan support. Their goal: to find the right balance between economic growth, public health, environmental preservation and regulation.
The group’s research found that Texas is one of seven states without comprehensive APO regulations. That leaves APOs in Texas largely unchecked and out-of-control.
Video Examines Six Major Concerns
Excessive sedimentation that leads to flooding is not the only issue associated with aggregate mining as practiced in Texas. The video shows APO operations across the state and addresses six major concerns:
Air particulate emissions
Water quality and availability
Surface and groundwater contamination, and flooding
Rapid development of APOs with adequate regulatory oversight
Truck traffic, safety, and road repairs plus their costs
Nuisance issues such as noise and light pollution, plus blasting
In case you want to do your own econometric analysis on the relationship between growth and aggregate regulation, TRAM offers a good starting point. This link shows a state-by-state breakdown of regulations. Who has comprehensive mining regulations, who has partial and who has none?
Of the ten fastest growing states, three have no comprehensive mining regulations; six do, and one has partial regulation. Net: the proposition that lax regulation of APOs creates fast growth is dubious.
Posted by Bob Rehak on 1/29/2021
1249 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.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2021/01/Screen-Shot-2021-01-29-at-4.22.33-PM.png?fit=1962%2C1104&ssl=111041962adminadmin2021-01-29 17:12:392021-01-29 17:17:21Texans for Responsible Aggregate Mining Release Video Showing Statewide Nature of Problems
Appendix F of the San Jacinto River Basin Master Drainage Plan discusses the sediment contribution to Lake Houston of various tributaries. It asserts that Cypress Creek, Spring Creek, and West Fork sub-watersheds are the highest contributors of suspended sediment to Lake Houston, contributing an estimated 38.7 percent, 26.8 percent, and 13.0 percent of the total sediment load, respectively.
However, to measure sediment on the West Fork, the study team used a gage at I-45 – UPSTREAM from virtually all West Fork sand mines. This explains a huge disparity between measured data and visual observations. But the report never even acknowledges the visual observations.
I have previously posted about the 3600-page master plan. In many respects, it is a masterpiece that contains good and valuable information that will help mitigate flooding throughout the watershed. The comments in this post relate ONLY to Appendix F on sedimentation, which in my opinion contains a serious flaw.
Misleading Impressions
The problem with using the gage at I-45: it rules out certain contributions to sedimentation that the report barely acknowledges.
Cypress Creek and Spring Creek combine before merging with the West Fork. Thus, you would expect five times more sediment coming from Spring and Cypress Creeks than the West Fork, based on their findings. Yet almost every time I photograph the confluence of the West Fork and Spring Creek, I see more sediment coming from the West Fork, despite the fact that Lake Conroe blocks sediment coming from the upper part of the watershed. See below.
Confluence of Spring Creek and West Fork San Jacinto. Each shot taken in a different month and from a different angle. But the siltier stream in each case is the West Fork where virtually all the sand mines are.
Location of West Fork Gage Never Fully Specified in Report
The West Fork gage number is listed on page 114 of Appendix F. But the description says only, “W Fk San Jacinto Rv nr Conroe Tx, Gage #08068000.” At another point (page 115), it lists the gage near Lake Conroe. To find the exact location of the gage, one must go outside the report to a USGS site. Then to see where the gage sits relative to West Fork sand mines, one must back up to page 61 of Appendix F. Most readers will just assume, given the scientific nature of the report, that the authors used a gage at a representative location, not one that ruled out sediment from sand mines.
Even a careful reader of the report could conclude that the contribution of sand mines to sedimentation is minor in the grand scheme of things. TACA would welcome such a conclusion.
The implications of measuring sediment upstream from sand mines, overlooking visual evidence, and ignoring official reports calls into question some of the report’s recommendations. For instance, #2 suggests using “existing [emphasis added] stream gage data” … to “inform where higher suspended sediment is originating within each sub-watershed.”
Breaches into drainage channels just a few yards upstream from the West Fork
Intentional breaches. Note the backhoe tracks and sharp edges to the breach in this video.
Sedimentation Report Needs More Gages
You can’t document the volume of such breaches and illegal pumping from a helicopter. However, you can’t overlook such practices either.
What we really need is a sediment gage downstream from the sand mines just before the West Fork joins Spring Creek. A gage at that location would go a long way toward calculating the volume of sediment escaping from sand mines.
Report Also Needs Revision Before Legislative Committees Meet on Sand Mining
The authors also need to amend this report quickly. The amendments should highlight the location of the West Fork gage, the implications of that, and limitations on the use of the data – especially by the legislature.
My biggest fear is that sand miners will attempt to use this report to defeat reasonable legislative reforms of the industry. They have used similar reports in the past to do exactly that. I have personally testified in four House and Senate committee hearings about sand mines only to have TACA trot out figures from the 2000 Brown and Root Study. B&R drew similar conclusions because it used the same West Fork gage at I-45.
To protect the scientific integrity of its report and the validity of its recommendations, the authors need to act quickly. The legislature is considering new sand mining regulations at this instant. Such regulations could protect downstream residents from excess man-made sedimentation, huge dredging costs and potential flooding.
The Master Drainage Plan, including Appendix F on sedimentation, is intended to guide flood mitigation efforts for the next 50 years and help inform the expenditure of potentially billions of dollars during that time. The larger report has many good points. But Appendix F is seriously flawed. I hope the partners – City of Houston, SJRA, Montgomery County, HCFCD and their consultants – fix it before lasting damage is done.
Posted by Bob Rehak on 1/28/2021
1248 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.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2021/01/Confluence-Montage.jpg?fit=1200%2C813&ssl=18131200adminadmin2021-01-28 16:17:192021-01-29 08:16:00San Jacinto Master Drainage Plan Uses Gage UPSTREAM from Sand Mines to Estimate West Fork Sedimentation
Scientists Quantify Flood-Damage-Reduction Benefit of Texas Wetlands
A study by Samuel D. Brody, Sammy Zahran, Wesley E. Highfield, Himanshu Grover, and Arnold Vedlitz called “Identifying the impact of the built environment on flood damage in Texas” quantifies the flood reduction benefits of wetlands along the Gulf coast. The authors studied property damage in 423 floods between 1997 and 2001. They identified the effect of several built-environment issues, including wetland alteration, impervious surface and dams on reported property damage while controlling for biophysical and socio-economic characteristics.
Their statistical results suggest that naturally occurring wetlands play a particularly important role in mitigating flood damage. But how much? The results vary by location, of course, but in one county, they discovered that a 3.4X increase in wetland alteration permits correlated to a 10X increase in flood damage.
Importance of Understanding Causes of Flooding
Floods damage more property than any other type of natural disaster in America – billions of dollars every year. However, the author’s say, there is lack of research on the relationship between the built environment and flood impacts in the eastern portion of Texas. Say the authors, “Such information is critical given the continued development of coastal areas and the increasing vulnerability of human populations to inland coastal flooding.”
What Study Correlated and How
The authors correlated flood property damage (total dollar loss adjusted by the consumer price index) to variables such as:
They measured everything by counties. Watershed data would have been better for floods, but damage is not often aggregated by watersheds.
Researchers measured “wetland alterations” by counting wetland permits issued by the US Army Corps of Engineers in Galveston under Section 404 of the Clean Water Act. They simply counted the number of permits issued up to the day of any given flood. This enabled them to measure the cumulative impact of wetland alterations over time.
FEMA’s Community Rating System encourages city and county leaders to promote responsible development over time. The more an area reduces flood damage through regulations, mapping and 18 flood mitigation measures, the higher the discounts that residents earn on flood insurance.
The researchers used multivariate regression analyses to find which factors most influenced the degree of flood damage in eastern Texas. Multivariate regression identifies the degree of influence that multiple variables have over each other. It measures correlation, not causation.
Major Findings
Specific characteristics of the human-built environment in eastern Texas have an important influence on property damage resulting from floods, even when controlling for biophysical and socio-economic factors. Below are four major findings from the study.
First. the amount and duration of precipitation associated with a given storm flood largely governs flood damage.
When looking at biophysical variables, timing of precipitation is particularly important. “Heavy precipitation the day before the actual flood event is by far the strongest predictor of total property damage,” say the authors. This may be because of the delay in the rise of water or the saturation of soil. “It is important for decision-makers and the public to understand that heavy precipitation followed by sunny skies can still result in significant flood damage the next day.”
Second, the most important built-environment indicator of flood damage is the the alteration of naturally occurring wetlands.
“Impervious surfaces have long been criticised for their contribution to increased flooding and associated damage. However, the most significant impact may not depend solely on the total amount of imperviousness in a watershed or drainage basin, but rather on where exactly these built surfaces are placed. Altering or removing a wetland to construct car parks, roads and rooftops, for instance, effectively eliminates its ability to capture, hold and store water run-off.”
Similarly, comparing two 1.5 inch rainfalls in Wharton County, damage doubled while the number of wetland-alteration permits increased from 17 to 26.
Incredibly, Galveston County experienced a 20X increase in flood damage based on two 0.09 inch rainfalls three years apart. During that time, the number of wetland permits increased from 546 to 921.
“Developments initially believed to be safe from flood threats become an unexpected target of expensive flood damage over time,” say the authors. “The planning goal in this situation is to allow development to proceed without reducing the hydrological function and value of wetland systems.”
The authors suggest that achieving this objective will involve identifying and protecting wetlands through local land use policies. They include zoning restrictions, land acquisition programs, clustered development, density bonuses and more. Net economic benefits to a locality may result by reducing costs related to repair of damaged structures and mitigation solutions.
Third, wetlands may be more effective than dams in mitigating property loss over time.
Dams are extremely costly mitigation alternatives. And they can encourage development in flood-prone areas out of a false sense of security. See more below.
Fourth, FEMA’s Community Rating System reduces property damage.
Communities ranked high by FEMA for mitigation measures experience significantly lower amounts of flood-related property damage. “In fact, CRS participation appears to reduce community-wide flood damage more than dams, which are far more costly,” the study claims.
Economic Tradeoffs
In comparing the relative effects of various variables on flood damage, the authors also assessed economic tradeoffs of various mitigation measures.
For instance, they compared the cost in property damage in a flood to the price of wetland permits and dams. They found that 129 wetland alteration permits cost as much property damage per flood as one dam saved.
“Given the expense of building dams, their negative environmental ramifications, and the possibility of structural failure, protecting naturally occurring wetlands may be a more rational policy alternative,” says the study.
Posted by Bob Rehak on 1/30/21 based on a study by Samuel Brody, et. al.
1250 Days since Hurricane Harvey
Texans for Responsible Aggregate Mining Release Video Showing Statewide Nature of Problems
Texans for Responsible Aggregate Mining (TRAM) released a new video today demonstrating statewide issues with aggregate production operators (APOs). Just in time for the 2021 legislative session, the 12-minute video calls the concerns non-partisan, but says they requiring bi-partisan support. Their goal: to find the right balance between economic growth, public health, environmental preservation and regulation.
The group’s research found that Texas is one of seven states without comprehensive APO regulations. That leaves APOs in Texas largely unchecked and out-of-control.
Video Examines Six Major Concerns
Excessive sedimentation that leads to flooding is not the only issue associated with aggregate mining as practiced in Texas. The video shows APO operations across the state and addresses six major concerns:
This vividly demonstrates some of the issues discussed in the House Interim Committee’s Report on Aggregate Production Operations released earlier this week.
Packed with Fascinating Factoids about Aggregate Mining
The video is packed with eye-opening factoids. Did you know, for instance, that:
Screen Capture Courtesy of TRAM. Click to play video.
Relationship Between Regulation and Growth
In case you want to do your own econometric analysis on the relationship between growth and aggregate regulation, TRAM offers a good starting point. This link shows a state-by-state breakdown of regulations. Who has comprehensive mining regulations, who has partial and who has none?
Of the ten fastest growing states, three have no comprehensive mining regulations; six do, and one has partial regulation. Net: the proposition that lax regulation of APOs creates fast growth is dubious.
Posted by Bob Rehak on 1/29/2021
1249 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.
San Jacinto Master Drainage Plan Uses Gage UPSTREAM from Sand Mines to Estimate West Fork Sedimentation
Appendix F of the San Jacinto River Basin Master Drainage Plan discusses the sediment contribution to Lake Houston of various tributaries. It asserts that Cypress Creek, Spring Creek, and West Fork sub-watersheds are the highest contributors of suspended sediment to Lake Houston, contributing an estimated 38.7 percent, 26.8 percent, and 13.0 percent of the total sediment load, respectively.
However, to measure sediment on the West Fork, the study team used a gage at I-45 – UPSTREAM from virtually all West Fork sand mines. This explains a huge disparity between measured data and visual observations. But the report never even acknowledges the visual observations.
I have previously posted about the 3600-page master plan. In many respects, it is a masterpiece that contains good and valuable information that will help mitigate flooding throughout the watershed. The comments in this post relate ONLY to Appendix F on sedimentation, which in my opinion contains a serious flaw.
Misleading Impressions
The problem with using the gage at I-45: it rules out certain contributions to sedimentation that the report barely acknowledges.
Cypress Creek and Spring Creek combine before merging with the West Fork. Thus, you would expect five times more sediment coming from Spring and Cypress Creeks than the West Fork, based on their findings. Yet almost every time I photograph the confluence of the West Fork and Spring Creek, I see more sediment coming from the West Fork, despite the fact that Lake Conroe blocks sediment coming from the upper part of the watershed. See below.
Location of West Fork Gage Never Fully Specified in Report
The West Fork gage number is listed on page 114 of Appendix F. But the description says only, “W Fk San Jacinto Rv nr Conroe Tx, Gage #08068000.” At another point (page 115), it lists the gage near Lake Conroe. To find the exact location of the gage, one must go outside the report to a USGS site. Then to see where the gage sits relative to West Fork sand mines, one must back up to page 61 of Appendix F. Most readers will just assume, given the scientific nature of the report, that the authors used a gage at a representative location, not one that ruled out sediment from sand mines.
The report ignored thousands of photos posted on ReduceFlooding.com as well as TCEQ reports citing sand mines for non-compliance.
The implications of measuring sediment upstream from sand mines, overlooking visual evidence, and ignoring official reports calls into question some of the report’s recommendations. For instance, #2 suggests using “existing [emphasis added] stream gage data” … to “inform where higher suspended sediment is originating within each sub-watershed.”
Sorry, you can’t get there from I-45. And if sand mines are an issue, neither can you get there from LIDAR surveys taken every several years, which the report also recommends. Sand mine discharges happen frequently and sporadically, often under the cover of darkness.
Sand Mining Not Seriously Considered as Possible Source of Sedimentation
The report, for the most part, blames sedimentation on new development and stream bank erosion. It does not consider:
Sedimentation Report Needs More Gages
You can’t document the volume of such breaches and illegal pumping from a helicopter. However, you can’t overlook such practices either.
What we really need is a sediment gage downstream from the sand mines just before the West Fork joins Spring Creek. A gage at that location would go a long way toward calculating the volume of sediment escaping from sand mines.
Report Also Needs Revision Before Legislative Committees Meet on Sand Mining
The authors also need to amend this report quickly. The amendments should highlight the location of the West Fork gage, the implications of that, and limitations on the use of the data – especially by the legislature.
My biggest fear is that sand miners will attempt to use this report to defeat reasonable legislative reforms of the industry. They have used similar reports in the past to do exactly that. I have personally testified in four House and Senate committee hearings about sand mines only to have TACA trot out figures from the 2000 Brown and Root Study. B&R drew similar conclusions because it used the same West Fork gage at I-45.
To protect the scientific integrity of its report and the validity of its recommendations, the authors need to act quickly. The legislature is considering new sand mining regulations at this instant. Such regulations could protect downstream residents from excess man-made sedimentation, huge dredging costs and potential flooding.
The Master Drainage Plan, including Appendix F on sedimentation, is intended to guide flood mitigation efforts for the next 50 years and help inform the expenditure of potentially billions of dollars during that time. The larger report has many good points. But Appendix F is seriously flawed. I hope the partners – City of Houston, SJRA, Montgomery County, HCFCD and their consultants – fix it before lasting damage is done.
Posted by Bob Rehak on 1/28/2021
1248 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.