The San Jacinto Regional Flood Planning Group (SJRFPG) submitted its final recommendations to the Texas Water Development Board on January 10. The 316-page report includes recommendations on floodplain management evaluation, strategies and projects; the plan’s impacts; administration, regulatory and legislative recommendations; and financing.
I discussed the floodplain projects and impacts when I reviewed the draft plan in August of 2022. Not much as changed with the projects and impacts except for some minor details.
In 2019, the legislature appropriated money to establish the FIF. However, it did not appropriate additional funds in 2021. We need more money to fully implement the plans in the coming years.
Provide state incentives to establish dedicated drainage funding:
State law provides municipalities with the authority to establish local drainage utilities. Those that don’t use that authority generally rely on federal partners to fund floodplain management and regulatory programs. Or else they use some combination of general tax revenues and municipal bonds. The state should incentivize local communities to fund drainage projects rather than rely solely on federal funding.
Provide counties with legislative authority to establish drainage utilities/fees:
Municipalities have that power. But the unincorporated areas of counties do not. Give counties a reliable source of revenue to implement, maintain and repair drainage projects. Let them establish drainage utilities and drainage fees in unincorporated areas.
Update the state building code on a regular basis:
Texas is missing out on a billion dollars in FEMA’s Building Resilient Infrastructure and Communities (BRIC) Grants because of antiquated building costs. To take advantage of those grants, we need to update building codes. Adopt recent versions of the International Building Code (IBC) and the International Residential Code (IRC) at a minimum. Also we should adopt updated codes regularly in future legislative sessions.
Regulatory and Administrative Recommendations
The plan also made the following recommendations for regulatory and administrative changes.
Upgrade TxDOT design criteria:
Require all new and reconstructed state roadways to be elevated at or above the Atlas-14 1.0% annual chance flood level. Use the 0.2% level if Atlas 14 has not yet been adopted. TxDOT should also consider future conditions, such as urbanization and climate variability, in its roadway design criteria. TxDOT does not in all cases design roadways consistent with minimum NFIP requirements. TxDOT should strive to meet NFIP standards, especially for critical infrastructure such as evacuation and emergency routes.
Recommend Minimum Statewide Building Elevation Standards:
Recommend statewide minimum finished floor elevations at (or waterproofed to) the FEMA effective 2% annual chance flood except in areas designated as coastal flood zones. Use the 1.0% annual chance flood elevation where Atlas 14 has been adopted. Incentivize higher building standards. Recent historic floods and NOAA’s updated Atlas-14 rainfall probabilities reveal how much base flood elevations (BFE) can change over time. Jurisdictions that have required a freeboard over the current BFE have mitigated the risk of these increasing BFEs.
Clarify the process and cost to turn Base Level Engineering (BLE) data into Flood Insurance Rate Map (FIRM) panels:
BLE efficiently models and maps flood hazard data at community, county, watershed, and/or state levels. Currently, the state and FEMA are heavily investing in BLE. Clearly communicate to local jurisdictions how to implement this data in regulations and flood insurance rate maps. The steps remain unclear to many local jurisdictions.
Establish and fund a levee safety program similar to the TCEQ dam-safety program:
The TCEQ has a program to inspect dams that fall under its jurisdiction. Levees, on the other hand, are not subject to a similar safety program despite posing similar risks during flooding events.
Promote flood awareness, education, safety and outreach:
Partner with the Texas Floodplain Managers Association (TFMA) to promote public flood awareness, education, and safety in communities. Also, partner with Texas Association of Counties to do the same for Floodplain Administrators lacking technical flooding background (e.g., some County Judges). A well-informed public can make better informed personal choices regarding issues that involve flood risk and also will be more likely to support public policies and mitigation measures to reduce that risk.
Support ongoing education/training for floodplain management:
Provide no- or low-cost online resources including training modules, webinars, and print. Target training for non-technical Floodplain Administrators (e.g., County Judges who may serve as Floodplain Administrators but not have the necessary technical background). This would help to make effective floodplain management more prevalent across the state, especially in smaller counties.
Develop state incentives to participate in the National Flood Insurance Program (NFIP) and Community Rating System (CRS) program:
NFIP works with communities to adopt and enforce floodplain management regulations that help mitigate flooding. CRS encourages practices that exceed minimum requirements of the NFIP. Both programs are essential to achieving State Flood-Plan goals. Implement State-led incentives to encourage communities to participate.
Develop a public database that tracks flood fatalities:
Fatalities have occurred during extreme flood events throughout the state’s history. A statewide database and tracking system with appropriate privacy restrictions could aid in future project planning and regulatory decision making. It could also help with future education efforts regarding actions that frequently lead to fatalities. An example is the importance of not attempting to drive through flood waters.
Help smaller jurisdictions prepare grant and loan applications or make the process easier:
Provide training for Councils of Governments (COGs) to assist with the funding process. Developing applications for project funding can be difficult, especially for smaller jurisdictions with limited experience and access to funding to obtain expert assistance. Simplifying applications and making funding available specifically for application development would serve to make the process more accessible across the state and help close knowledge gaps.
Develop interactive models that use Base Level Engineering (BLE) data:
Provide them to Regional Flood Planning Groups and their technical consulting teams. Standardize future conditions and land use data. The State’s and FEMA’s BLE data should be available in most parts of the state.
Allow partnerships to provide regional flood-mitigation solutions:
Flood risk does not recognize jurisdictional boundaries, yet many flood-mitigation programs prevent multiple jurisdictions from working together if they want to remain eligible state funding. Flood-mitigation studies and solutions require inter-jurisdictional collaboration. Update policies to encourage and permit it.
Next Step on Final Recommendations
These final recommendations sound like good ideas to me. Please communicate your feelings to your state senator and representative.
I have summarized the final recommendations above. To see their exact text, review chapter 8. Or see the entire report to put them all in context.
Posted by Bob Rehak on 1/22/2023
1972 Days After Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2023/01/20230121-Screenshot-2023-01-21-at-9.54.40-PM.jpg?fit=1200%2C788&ssl=17881200adminadmin2023-01-21 21:57:432023-01-21 23:33:14San Jacinto Regional Flood Planning Group Submits Final Recommendations
On January 10, 2023, McGehee ☆ Chang, Landgraf, Feiler responded to the government’s most recent motion in the Addicks Barker Downstream “Takings” Case on behalf of the plaintiffs. Their response included a counter-motion against the government. Here is a copy of their motion. Each side will have a chance to file one more round of written arguments before trial.
Background: Government Denies Claims
To recap, in November 2022, the government again moved for a summary judgment in the case. The government contended that the Addicks and Barker dams:
Historically prevented far more damage ($16.5 billion through 2016) than the release of water during Harvey caused
Reduced plaintiff’s level of flooding by up to 7-8 feet
Did not “cause” – in a legal sense – the plaintiffs’ flooding
Further, the government contended that plaintiffs’ claims are based on a single, extraordinary, catastrophic event and any action undertaken by the Corps during the event does not constitute a “taking” under the Fifth Amendment.
The government compared peak flows at several points along Buffalo Bayou during Harvey and contended that the plaintiffs properties would have flooded regardless of the release. It claims that the releases constituted less than 10% of total flow. The government also claimed that had it never built the dams, downstream flooding would have been far worse.
Plaintiffs Allege They Were Not Informed of Risk
The plaintiff’s response (which included 3800+ pages of arguments, depositions and appendices) focuses on how the government modified the dams and its procedures over time.
It adjusted discharge rates to maintain a “non-damaging channel capacity over time.” The rates went from the original design concept of 15,700 cubic feet per second down to about 2,000 cubic feet per second in a series of incremental steps over decades. The changes were designed to accommodate residential construction along Buffalo Bayou.
The plaintiffs allege that the Corps publicly reassured property owners that it would not open the dams to a point where it would cause downstream flooding. Plaintiffs further allege that over the years, people grew to rely on these assurances and none of the test properties experienced any flooding.
Nor did any of them know that the Government might deliberately release water from the Reservoirs in sufficient quantities to flood their properties.
One commercial property reported just a few inches of flooding prior to the releases, escalating to six feet afterward. Plaintiffs argue that they would have suffered no or substantially less flooding if the government had not released water, a decision motivated in part to protect upstream properties.
Crux of Plaintiff’s Arguments
Plaintiffs claim the government:
Repeatedly promised downstream property owners that it would keep the floodgates closed
Could have kept the floodgates closed; the Reservoirs were never in danger of failing
Elected to open the floodgates even though it did not have to do so to avoid any imminent failure
Knew that opening the floodgates would flood the downstream property owners
Cannot meet the high bar required to assert releases were necessary.
Could have bought-out the properties it flooded but chose not to because of the expense.
Plaintiffs conclude by saying that:
The Government’s summary judgment motion should be denied
The Court should enter a partial summary judgment for the Plaintiffs on the liability and causation elements of their claims
All other issues, including damages, should be set for a prompt trial.
To review all the appendices submitted by plaintiffs, click here. Size caution: 330 megabytes.
A Shakespearean Tragedy
Although it might be buried somewhere in thousands of pages of filings, neither side in this case appears to directly address which properties would have flooded regardless of the release and which flooded because of the release.
The government seems to contend it is responsible for none of the flooding because it was unavoidable. And the plaintiffs contend the government is responsible for all of it.
This is like watching a Shakespearean tragedy unfold. Not even at issue here are the policies that allowed lucrative development in dangerous places, the lack of risk disclosure, and the erosion of safety margins.
Next up: The government can reply to plaintiff’s motion by February 9, 2023. Plaintiffs will then have a chance to reply to the reply by March 11. Then both sides will gear up for a hearing before the Judge.
Posted by Bob Rehak on 1/19/2023
1969 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/2023/01/20230119-Screenshot-2023-01-19-at-12.18.25-PM.jpg?fit=1200%2C625&ssl=16251200adminadmin2023-01-19 12:24:482023-01-19 12:27:59Downstream Addicks Barker Case Moves Another Step Closer to Trial
The sky darkens. Thunder grows louder. Suddenly, the rain comes down so hard you can barely see. Soon, water starts coming over the curb toward your house. Your weather radio crackles with warnings. And when it’s over, the stormwater has stopped just feet from your door. Close call! But then you wonder. How intense was that storm? And does it really matter?
The answers affect disaster planning, flood insurance, mitigation, and more.
Consider the intensity question first.
How Intense Was That Storm?
Was it a 1-, 2-, 5-, 10-, 25-, 50- or 100-year storm?
Determining the intensity requires more than just reading your rain gage. That’s because intensity depends on volume within a certain time period. Five inches of rain in an hour should concern you far more than in a day.
Start by going to the Harris County Flood Warning System. It shows all official gages in the region. Hover over any one. A box with a hyperlink will pop up. For this example, let’s assume you live near the East Fork San Jacinto and FM1485.
Hovering over the gage by New Caney pulled up box with the blue link.
Click on the More Information link. It will lead you to a search screen that lets you specify date(s). You can also specify time ranges from one hour to one year.
In this case, I selected 2 days and adjusted the date until I captured all the significant rainfall.
By experimenting with different time ranges, you can narrow down the start and stop times. This is crucial, because intensity depends on both quantity and duration.
At our sample gage, I learned that rainfall from Tropical Storm Imelda in 2019 happened over a two-day time period.
Now, look up the total (28.68 inches) in the Atlas-14 table below. This table shows the rainfall precipitation frequency estimates for the Lake Houston Area.
So, how intense was that storm? The total rain for two days – 28.68 inches – qualifies Imelda as a 500-year storm at that gage. Look down to the 2-Day line and then across to the 500-year column.
If you captured more or less rain in your rain gage at home, use that total instead. At least now you know that you’re working with a 2-day event. (Note: some rain fell outside this range, but not much.)
Check other Gages to See Geographic Rainfall Distribution
While you’re exploring the Flood Warning System, check several different gages, especially those upstream. Rainfall can vary considerably within short distances.
For instance, during Imelda, a gage at the West Fork and SH242 showed only 13 inches of rain during an identical period – less than half the rain just a few miles west. That ranks as a 25-year storm, not a 500!
When people say that “We got X number of 500-year storms in Y years,” it’s important to remember that the 500-year designation applies only to a particular gage, not an entire region.
Do 500-Year Storms Mean 500-Year Floods?
Also remember this. As the example above shows, having a 500-year storm somewhere near you does not automatically mean you will experience a 500-year flood. It depends on where the rain falls in your watershed. If it falls upstream, it could result in a 500-year flood. But if it falls downstream, it will not.
During Imelda, the gage(s) at:
Greens Bayou and US59 got 15 inches – between a 25- and 50-year rain.
Spring Creek and I-45 got 8 inches – a 5-year rain.
Cypress Creek and US290 got 2.52 inches, not even a 1-year rain.
Lake Creek at Dobbin got 1.52 inches.
Lake Conroe at 1375 got .84 inches.
Use the drop-down list of gages to explore rainfall rates elsewhere.
A few miles in each case separated Armageddon from something far more manageable.
What Can You Do with This Information?
This exercise can help protect you in several ways. For instance:
If you didn’t flood during Imelda and you heard it was a 500-year rain, you might assume you didn’t need flood insurance. That could be a financially devastating miscalculation.
If you get little rain upstream and still flood, you should investigate why.
If you flood frequently on small rains, you need to investigate the causes and mitigation. Engage with HCFCD, your county engineer or floodplain manager. Perhaps the floodplain has been altered by upstream development. Perhaps the stream near you has become clogged. Perhaps you need to elevate your home or seek a buyout.
The more you know, the safer you’ll be.
Posted by Bob Rehak on 1/18/23
1968 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/2023/01/CallbackPanelPartial-2.png?fit=820%2C400&ssl=1400820adminadmin2023-01-18 17:14:232023-01-18 17:24:09How Intense Was That Storm? And Why Does It Matter?
San Jacinto Regional Flood Planning Group Submits Final Recommendations
The San Jacinto Regional Flood Planning Group (SJRFPG) submitted its final recommendations to the Texas Water Development Board on January 10. The 316-page report includes recommendations on floodplain management evaluation, strategies and projects; the plan’s impacts; administration, regulatory and legislative recommendations; and financing.
I discussed the floodplain projects and impacts when I reviewed the draft plan in August of 2022. Not much as changed with the projects and impacts except for some minor details.
Now, with the state legislature in session, I would like to review the administrative, regulatory and legislative final recommendations in Chapter 8.
Legislative Recommendations
The SJRPG made four legislative recommendations to facilitate floodplain management plus flood mitigation planning and implementation.
Provide recurring biennial appropriations to the Flood Infrastructure Fund (FIF):
In 2019, the legislature appropriated money to establish the FIF. However, it did not appropriate additional funds in 2021. We need more money to fully implement the plans in the coming years.
Provide state incentives to establish dedicated drainage funding:
State law provides municipalities with the authority to establish local drainage utilities. Those that don’t use that authority generally rely on federal partners to fund floodplain management and regulatory programs. Or else they use some combination of general tax revenues and municipal bonds. The state should incentivize local communities to fund drainage projects rather than rely solely on federal funding.
Provide counties with legislative authority to establish drainage utilities/fees:
Municipalities have that power. But the unincorporated areas of counties do not. Give counties a reliable source of revenue to implement, maintain and repair drainage projects. Let them establish drainage utilities and drainage fees in unincorporated areas.
Update the state building code on a regular basis:
Texas is missing out on a billion dollars in FEMA’s Building Resilient Infrastructure and Communities (BRIC) Grants because of antiquated building costs. To take advantage of those grants, we need to update building codes. Adopt recent versions of the International Building Code (IBC) and the International Residential Code (IRC) at a minimum. Also we should adopt updated codes regularly in future legislative sessions.
Regulatory and Administrative Recommendations
The plan also made the following recommendations for regulatory and administrative changes.
Upgrade TxDOT design criteria:
Require all new and reconstructed state roadways to be elevated at or above the Atlas-14 1.0% annual chance flood level. Use the 0.2% level if Atlas 14 has not yet been adopted. TxDOT should also consider future conditions, such as urbanization and climate variability, in its roadway design criteria. TxDOT does not in all cases design roadways consistent with minimum NFIP requirements. TxDOT should strive to meet NFIP standards, especially for critical infrastructure such as evacuation and emergency routes.
Recommend Minimum Statewide Building Elevation Standards:
Recommend statewide minimum finished floor elevations at (or waterproofed to) the FEMA effective 2% annual chance flood except in areas designated as coastal flood zones. Use the 1.0% annual chance flood elevation where Atlas 14 has been adopted. Incentivize higher building standards. Recent historic floods and NOAA’s updated Atlas-14 rainfall probabilities reveal how much base flood elevations (BFE) can change over time. Jurisdictions that have required a freeboard over the current BFE have mitigated the risk of these increasing BFEs.
Clarify the process and cost to turn Base Level Engineering (BLE) data into Flood Insurance Rate Map (FIRM) panels:
BLE efficiently models and maps flood hazard data at community, county, watershed, and/or state levels. Currently, the state and FEMA are heavily investing in BLE. Clearly communicate to local jurisdictions how to implement this data in regulations and flood insurance rate maps. The steps remain unclear to many local jurisdictions.
Establish and fund a levee safety program similar to the TCEQ dam-safety program:
The TCEQ has a program to inspect dams that fall under its jurisdiction. Levees, on the other hand, are not subject to a similar safety program despite posing similar risks during flooding events.
Promote flood awareness, education, safety and outreach:
Partner with the Texas Floodplain Managers Association (TFMA) to promote public flood awareness, education, and safety in communities. Also, partner with Texas Association of Counties to do the same for Floodplain Administrators lacking technical flooding background (e.g., some County Judges). A well-informed public can make better informed personal choices regarding issues that involve flood risk and also will be more likely to support public policies and mitigation measures to reduce that risk.
Support ongoing education/training for floodplain management:
Provide no- or low-cost online resources including training modules, webinars, and print. Target training for non-technical Floodplain Administrators (e.g., County Judges who may serve as Floodplain Administrators but not have the necessary technical background). This would help to make effective floodplain management more prevalent across the state, especially in smaller counties.
Develop state incentives to participate in the National Flood Insurance Program (NFIP) and Community Rating System (CRS) program:
NFIP works with communities to adopt and enforce floodplain management regulations that help mitigate flooding. CRS encourages practices that exceed minimum requirements of the NFIP. Both programs are essential to achieving State Flood-Plan goals. Implement State-led incentives to encourage communities to participate.
Develop a public database that tracks flood fatalities:
Fatalities have occurred during extreme flood events throughout the state’s history. A statewide database and tracking system with appropriate privacy restrictions could aid in future project planning and regulatory decision making. It could also help with future education efforts regarding actions that frequently lead to fatalities. An example is the importance of not attempting to drive through flood waters.
Help smaller jurisdictions prepare grant and loan applications or make the process easier:
Provide training for Councils of Governments (COGs) to assist with the funding process. Developing applications for project funding can be difficult, especially for smaller jurisdictions with limited experience and access to funding to obtain expert assistance. Simplifying applications and making funding available specifically for application development would serve to make the process more accessible across the state and help close knowledge gaps.
Develop interactive models that use Base Level Engineering (BLE) data:
Provide them to Regional Flood Planning Groups and their technical consulting teams. Standardize future conditions and land use data. The State’s and FEMA’s BLE data should be available in most parts of the state.
Allow partnerships to provide regional flood-mitigation solutions:
Flood risk does not recognize jurisdictional boundaries, yet many flood-mitigation programs prevent multiple jurisdictions from working together if they want to remain eligible state funding. Flood-mitigation studies and solutions require inter-jurisdictional collaboration. Update policies to encourage and permit it.
Next Step on Final Recommendations
These final recommendations sound like good ideas to me. Please communicate your feelings to your state senator and representative.
I have summarized the final recommendations above. To see their exact text, review chapter 8. Or see the entire report to put them all in context.
Posted by Bob Rehak on 1/22/2023
1972 Days After Hurricane Harvey
Downstream Addicks Barker Case Moves Another Step Closer to Trial
On January 10, 2023, McGehee ☆ Chang, Landgraf, Feiler responded to the government’s most recent motion in the Addicks Barker Downstream “Takings” Case on behalf of the plaintiffs. Their response included a counter-motion against the government. Here is a copy of their motion. Each side will have a chance to file one more round of written arguments before trial.
Background: Government Denies Claims
To recap, in November 2022, the government again moved for a summary judgment in the case. The government contended that the Addicks and Barker dams:
Further, the government contended that plaintiffs’ claims are based on a single, extraordinary, catastrophic event and any action undertaken by the Corps during the event does not constitute a “taking” under the Fifth Amendment.
The government compared peak flows at several points along Buffalo Bayou during Harvey and contended that the plaintiffs properties would have flooded regardless of the release. It claims that the releases constituted less than 10% of total flow. The government also claimed that had it never built the dams, downstream flooding would have been far worse.
Plaintiffs Allege They Were Not Informed of Risk
The plaintiff’s response (which included 3800+ pages of arguments, depositions and appendices) focuses on how the government modified the dams and its procedures over time.
It adjusted discharge rates to maintain a “non-damaging channel capacity over time.” The rates went from the original design concept of 15,700 cubic feet per second down to about 2,000 cubic feet per second in a series of incremental steps over decades. The changes were designed to accommodate residential construction along Buffalo Bayou.
The plaintiffs allege that the Corps publicly reassured property owners that it would not open the dams to a point where it would cause downstream flooding. Plaintiffs further allege that over the years, people grew to rely on these assurances and none of the test properties experienced any flooding.
Nor did any of them know that the Government might deliberately release water from the Reservoirs in sufficient quantities to flood their properties.
One commercial property reported just a few inches of flooding prior to the releases, escalating to six feet afterward. Plaintiffs argue that they would have suffered no or substantially less flooding if the government had not released water, a decision motivated in part to protect upstream properties.
Crux of Plaintiff’s Arguments
Plaintiffs claim the government:
Plaintiffs conclude by saying that:
To review all the appendices submitted by plaintiffs, click here. Size caution: 330 megabytes.
A Shakespearean Tragedy
Although it might be buried somewhere in thousands of pages of filings, neither side in this case appears to directly address which properties would have flooded regardless of the release and which flooded because of the release.
The government seems to contend it is responsible for none of the flooding because it was unavoidable. And the plaintiffs contend the government is responsible for all of it.
This is like watching a Shakespearean tragedy unfold. Not even at issue here are the policies that allowed lucrative development in dangerous places, the lack of risk disclosure, and the erosion of safety margins.
Next up: The government can reply to plaintiff’s motion by February 9, 2023. Plaintiffs will then have a chance to reply to the reply by March 11. Then both sides will gear up for a hearing before the Judge.
Posted by Bob Rehak on 1/19/2023
1969 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 Intense Was That Storm? And Why Does It Matter?
The sky darkens. Thunder grows louder. Suddenly, the rain comes down so hard you can barely see. Soon, water starts coming over the curb toward your house. Your weather radio crackles with warnings. And when it’s over, the stormwater has stopped just feet from your door. Close call! But then you wonder. How intense was that storm? And does it really matter?
The answers affect disaster planning, flood insurance, mitigation, and more.
Consider the intensity question first.
How Intense Was That Storm?
Was it a 1-, 2-, 5-, 10-, 25-, 50- or 100-year storm?
Determining the intensity requires more than just reading your rain gage. That’s because intensity depends on volume within a certain time period. Five inches of rain in an hour should concern you far more than in a day.
Start by going to the Harris County Flood Warning System. It shows all official gages in the region. Hover over any one. A box with a hyperlink will pop up. For this example, let’s assume you live near the East Fork San Jacinto and FM1485.
Click on the More Information link. It will lead you to a search screen that lets you specify date(s). You can also specify time ranges from one hour to one year.
By experimenting with different time ranges, you can narrow down the start and stop times. This is crucial, because intensity depends on both quantity and duration.
At our sample gage, I learned that rainfall from Tropical Storm Imelda in 2019 happened over a two-day time period.
Now, look up the total (28.68 inches) in the Atlas-14 table below. This table shows the rainfall precipitation frequency estimates for the Lake Houston Area.
So, how intense was that storm? The total rain for two days – 28.68 inches – qualifies Imelda as a 500-year storm at that gage. Look down to the 2-Day line and then across to the 500-year column.
If you captured more or less rain in your rain gage at home, use that total instead. At least now you know that you’re working with a 2-day event. (Note: some rain fell outside this range, but not much.)
Check other Gages to See Geographic Rainfall Distribution
While you’re exploring the Flood Warning System, check several different gages, especially those upstream. Rainfall can vary considerably within short distances.
For instance, during Imelda, a gage at the West Fork and SH242 showed only 13 inches of rain during an identical period – less than half the rain just a few miles west. That ranks as a 25-year storm, not a 500!
When people say that “We got X number of 500-year storms in Y years,” it’s important to remember that the 500-year designation applies only to a particular gage, not an entire region.
Do 500-Year Storms Mean 500-Year Floods?
Also remember this. As the example above shows, having a 500-year storm somewhere near you does not automatically mean you will experience a 500-year flood. It depends on where the rain falls in your watershed. If it falls upstream, it could result in a 500-year flood. But if it falls downstream, it will not.
During Imelda, the gage(s) at:
Use the drop-down list of gages to explore rainfall rates elsewhere.
A few miles in each case separated Armageddon from something far more manageable.
What Can You Do with This Information?
This exercise can help protect you in several ways. For instance:
The more you know, the safer you’ll be.
Posted by Bob Rehak on 1/18/23
1968 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.