Yesterday, I published on this website the 32-page Final Hurricane Harvey Flood Report from Harris County Flood Control. Today someone asked me, “What was the biggest surprise in it?” Talk about pressure! Harris County packed lots of meat into those 32 pages! I pondered the question all morning and connected the following dots.
Five Times the Average Flow of Niagra Falls
For me, the biggest surprises were the volume of water going over the Lake Houston Dam and where it came from. At the peak of the storm, the amount of water going over the dam exceeded the volume ofNiagra Falls on an average day by 5X. The final figures actually show more water than previously thought going over the spillway: 491,800 cubic feet per second (cfs) vs. 450,000 cfs previously estimated, an increase of almost 10 percent.
More Flow From East Fork than West
When you look at where all that water came from, there was another surprise. More came from the East Fork than the West! See page 12.
In the East Fork numbers, include Peach Creek, Caney Creek and Luce Bayou; In the West Fork numbers, include Spring Creek and Cypress Creek.
One Third of West Fork Flow Came From Lake Conroe Dam Release
Roughly 240,000 cfs came down the West Fork. Seventy-nine thousand cfs came from the release at the Lake Conroe Dam, according to SJRA estimates. So ONE THIRD of the water coming down the West Fork at its peak was from the release. That’s important for the following reason.
Previously, SJRA indicated the Conroe release was approximately 15 percent of all the water going into Lake Houston. While technically true, this observation clouds the picture of what happened on the West Fork. The West Fork sustained 2.5x more damage than the East Fork and the main body of the lake COMBINED. (See Page 14). Survivor interviews suggest that much of that damage did not happen until the release from Lake Conroe!
Conclusion: Multiple Mitigation Measures Needed
That extra 79,000 cfs underscores the need to:
Temporarily lower the level of Lake Conroe during the peak of hurricane season
Enhance the carrying capacity and velocity of the West Fork through dredging
Add upstream retention that helps offset Lake Conroe releases
Add flood gates to Lake Houston.
The last item would increase the release rate of the Lake Houston dam during a major storm. The additional discharge capacity of the ten gates proposed by Mayor Turner could easily equal the 80,000 cfs discharged from Lake Conroe, eliminating a bottleneck on the river.
Of course, if we get another Harvey, many people will flood. No surprise there. But these measures should help reduce the damage, and perhaps eliminate it when we have smaller events, such as the Tax and Memorial Day Floods of 2015 and 2016.
Posted 6/5/2018 by Bob Rehak
280 Days since Hurricane Harvey
00adminadmin2018-06-05 23:40:182018-06-05 23:40:18Surprise in Final Harvey Report
Jeff Lindner, Director Hydrologic Operations and a meteorologist with the Harris County Flood Control District, just released a fascinating compendium of statistics: the Final Harvey Report. It contains everything you need to know to impress your friends, relatives and someday, your great, great grandchildren. When they’re sitting on your knee someday, you can tell them how you survived the greatest flood since Noah.
Ultimate Guide to the Wrath of Harvey
This is the Hurricane Harvey equivalent of the Baseball Encyclopedia. It contains scorecards for every part of the county. Hollywood could start a game show with this document – Wheel of Misfortune!
The Final Harvey Report details the catastrophic devastation from Harvey flooding that occurred all across Harris County. It also puts the storm in historic context and compares it to other previous record storms. Find statistics on:
House flooding by watershed and jurisdiction
Vehicle Damage
Rainfall statistics (duration, totals, intensity by location, probabilities, % over previous records, peak distribution)
Insurance claims and coverage
Channel flooding, stream flow and gage statistics
And more…much more
Did You Know? A Sampling of Statistics from Final Harvey Report
Volume of flows entering Lake Houston from the San Jacinto Watershed
Want to know the peak inflow to Lake Houston? 491,800 cubic feet per second.
How high was the peak flow over the spillway at the Lake Houston Dam? 425,000 cfs.
What is that equivalent to? 5 times the average flow of Niagra Falls.
What was the max rainfall in one hour? 6.8 inches!
What’s the expected recurrence interval for getting 6.8 inches again in one hour? 1500 years!
How many times were 1″-rainfall-in-15-minute alarms triggered during the storm? 336 times!
Of the 154,170 estimated homes flooded across Harris County only 36% had active flood insurance policies in place the day before Harvey…64% did not have flood insurance.
Of the 154,170 homes flooded 105,340 were outside the mapped 1% (100-yr) floodplain and were not required to have flood insurance. The 154,170 is between 9-12% of the total number of structures in Harris County.
The meeting sponsored by Harris County Flood Control in Kingwood to explain the upcoming $2.5 billion flood bond is being rescheduled. The rescheduling is so that County Judge Ed Emmett can attend.
The giant, new dune constricts the cross section of the East Fork by at least 50% near East End Park (background). Note how the dune reaches tree tops. The Army Corps emergency dredging project will not affect anything on the East Fork, so it is important that we put issues, such as this on the County’s flood bond agenda.
Originally the meeting was to have been held at the Kingwood Community Center on June 14 from 6-8pm. That meeting date has been cancelled and will be reset.
June 14 Meeting Harris County Flood Control District Bond Meeting Cancelled
No new date has been set yet. As soon as the new date has been finalized, I will post it on ReduceFlooding.com.
Thanks for your patience. Few things are more important for the future of our community than this flood bond.
Posted June 4, 2018
279 Days Since Hurricane Harvey
00adminadmin2018-06-04 16:59:092018-06-04 18:40:21Harris County Flood Control Meeting in Kingwood Will Be Rescheduled
Surprise in Final Harvey Report
Yesterday, I published on this website the 32-page Final Hurricane Harvey Flood Report from Harris County Flood Control. Today someone asked me, “What was the biggest surprise in it?” Talk about pressure! Harris County packed lots of meat into those 32 pages! I pondered the question all morning and connected the following dots.
Five Times the Average Flow of Niagra Falls
For me, the biggest surprises were the volume of water going over the Lake Houston Dam and where it came from. At the peak of the storm, the amount of water going over the dam exceeded the volume ofNiagra Falls on an average day by 5X. The final figures actually show more water than previously thought going over the spillway: 491,800 cubic feet per second (cfs) vs. 450,000 cfs previously estimated, an increase of almost 10 percent.
More Flow From East Fork than West
When you look at where all that water came from, there was another surprise. More came from the East Fork than the West! See page 12.
In the East Fork numbers, include Peach Creek, Caney Creek and Luce Bayou; In the West Fork numbers, include Spring Creek and Cypress Creek.
One Third of West Fork Flow Came From Lake Conroe Dam Release
Roughly 240,000 cfs came down the West Fork. Seventy-nine thousand cfs came from the release at the Lake Conroe Dam, according to SJRA estimates. So ONE THIRD of the water coming down the West Fork at its peak was from the release. That’s important for the following reason.
Previously, SJRA indicated the Conroe release was approximately 15 percent of all the water going into Lake Houston. While technically true, this observation clouds the picture of what happened on the West Fork. The West Fork sustained 2.5x more damage than the East Fork and the main body of the lake COMBINED. (See Page 14). Survivor interviews suggest that much of that damage did not happen until the release from Lake Conroe!
Conclusion: Multiple Mitigation Measures Needed
That extra 79,000 cfs underscores the need to:
The last item would increase the release rate of the Lake Houston dam during a major storm. The additional discharge capacity of the ten gates proposed by Mayor Turner could easily equal the 80,000 cfs discharged from Lake Conroe, eliminating a bottleneck on the river.
Of course, if we get another Harvey, many people will flood. No surprise there. But these measures should help reduce the damage, and perhaps eliminate it when we have smaller events, such as the Tax and Memorial Day Floods of 2015 and 2016.
Posted 6/5/2018 by Bob Rehak
280 Days since Hurricane Harvey
Final Harvey Report Puts Flood in Perspective
Jeff Lindner, Director Hydrologic Operations and a meteorologist with the Harris County Flood Control District, just released a fascinating compendium of statistics: the Final Harvey Report. It contains everything you need to know to impress your friends, relatives and someday, your great, great grandchildren. When they’re sitting on your knee someday, you can tell them how you survived the greatest flood since Noah.
Ultimate Guide to the Wrath of Harvey
This is the Hurricane Harvey equivalent of the Baseball Encyclopedia. It contains scorecards for every part of the county. Hollywood could start a game show with this document – Wheel of Misfortune!
The Final Harvey Report details the catastrophic devastation from Harvey flooding that occurred all across Harris County. It also puts the storm in historic context and compares it to other previous record storms. Find statistics on:
Did You Know? A Sampling of Statistics from Final Harvey Report
Volume of flows entering Lake Houston from the San Jacinto Watershed
Want to know the peak inflow to Lake Houston? 491,800 cubic feet per second.
How high was the peak flow over the spillway at the Lake Houston Dam? 425,000 cfs.
What is that equivalent to? 5 times the average flow of Niagra Falls.
What was the max rainfall in one hour? 6.8 inches!
What’s the expected recurrence interval for getting 6.8 inches again in one hour? 1500 years!
How many times were 1″-rainfall-in-15-minute alarms triggered during the storm? 336 times!
Of the 154,170 estimated homes flooded across Harris County only 36% had active flood insurance policies in place the day before Harvey…64% did not have flood insurance.
Of the 154,170 homes flooded 105,340 were outside the mapped 1% (100-yr) floodplain and were not required to have flood insurance. The 154,170 is between 9-12% of the total number of structures in Harris County.
Learn more. Read the full Final HCFCD Harvey Report,
Or check out the Houston Chronicle’s coverage of the subject.
Posted by Bob Rehak on 6/4/18
Day 279 Since Hurricane Harvey
Harris County Flood Control Meeting in Kingwood Will Be Rescheduled
The meeting sponsored by Harris County Flood Control in Kingwood to explain the upcoming $2.5 billion flood bond is being rescheduled. The rescheduling is so that County Judge Ed Emmett can attend.
The giant, new dune constricts the cross section of the East Fork by at least 50% near East End Park (background). Note how the dune reaches tree tops. The Army Corps emergency dredging project will not affect anything on the East Fork, so it is important that we put issues, such as this on the County’s flood bond agenda.
Originally the meeting was to have been held at the Kingwood Community Center on June 14 from 6-8pm. That meeting date has been cancelled and will be reset.
No new date has been set yet. As soon as the new date has been finalized, I will post it on ReduceFlooding.com.
Thanks for your patience. Few things are more important for the future of our community than this flood bond.
Posted June 4, 2018
279 Days Since Hurricane Harvey