Twenty-four hours ago, Hurricane Delta was simply potential tropical cyclone #26. As of 8 P.M. EDT today, the National Hurricane Center indicated #26 had progressed from tropical depression to tropical storm to hurricane in 24 hours. By tomorrow night, Delta should become a major hurricane as it crosses the resort areas on the northeastern tip of the Yucatan. However, the NHC also predicts that the storm will de-intensify before it makes landfall somewhere between East Texas and the Florida Panhandle on Friday.
Winds Could Increase from 75 to 120 mph
Low wind sheer and warm waters in the northwest Caribbean will allow rapid strengthening over the next 24 to 36 hours. The storm already has sustained winds of 75 mph. NHC gives a better than 50 percent chance of a 35-40 kt increase in wind speed over the next 24 hours. That’s roughly another 40 to 45 mph.
Track Shifts Slightly West
The NHC has shifted the track envelope westward over today, bringing the storm closer to Houston, though we are still slightly outside the cone.
Source: National Hurricane Center
Tropical Storm Force Winds Currently Extend 70 miles From Center
NHC expects additional rapid strengthening during the next day or so. Delta, they say, should become a major hurricane when it nears the Yucatan Peninsula. Hurricane-force winds extend outward up to 15 miles (25 km) from the center and tropical-storm-force winds extend up to 70 miles (110 km) from the center.
At this point, the Houston area has a 10-30% probability of experiencing tropical-storm-force winds from Delta.
Louisiana to Western Florida Faces Largest Danger
NHC advises, “Delta is forecast to approach the northern Gulf Coast late this week as a hurricane. While there is large uncertainty in the track and intensity forecasts, there is an increasing risk of dangerous storm surge, wind, and rainfall hazards along the coast from Louisiana to the western Florida Panhandle beginning Thursday night or Friday. Residents in these areas should ensure they have their hurricane plan in place and monitor updates to the forecast of Delta.”
Impact to Texas Coast?
Jeff Lindner, Harris County Meteorologist, says, “Swells will be increasing over the northwest Gulf of Mexico by mid week with heights increasing into the 5-10 foot range by Wednesday. This will result in increasing tides along the upper TX coast. Current projections indicate 1.0-1.5 feet above normal levels at times of high tides Thursday and Friday. This is subject to change based on the intensity and wind field of Delta over the central and NW Gulf late this week.”
While SE TX is currently outside the “error cone” and direct impacts appear unlikely, Lindner says that its important to closely monitor forecasts for any changes in the track.
Posted by Bob Rehak at 9PM on Monday, 10/5/2020based on data from the NHC and HCFCD
1133 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/10/234234.png?fit=897%2C738&ssl=1738897adminadmin2020-10-05 21:01:382020-10-05 21:17:11Delta Explodes into Hurricane; Should Become Major Hurricane by Wednesday; Track Shifts Slightly West
Aerial photos of the West Fork Mouth Bar show that the above-water portion on this once-massive sand bar is now down to the width of one excavator for most of its length. A mouth bar is a sand bar where the mouth of a river or stream meets a standing body of water, such as Lake Houston. As water slows when it reaches the standing water, sediment carried downstream drops out of suspension.
The Before Shot
The first photo below shows the West Fork Mouth Bar immediately after Harvey and before any remediation work took place.
Looking south toward Lake Houston and the FM1960 Bridge from Kingwood.Photo of West Fork Mouth Bar taken on 9/15/2017, about two weeks after Harvey.
At that point in time, the mouth bar extended five feet above water in places. It was 3/4 of a mile wide and a half mile from the northernmost part to the small island in the channel south of the bar. But the part you can’t see, below water, is even bigger.
This massive blockage backed water up throughout the Humble/Kingwood/Atascocita area, and contributed to the flooding of thousands of homes and businesses.
Today
I took the shot below on Sunday night, 10/4/2020. While the camera position and lens perspective are slightly different, they are close enough to show the progress made in removing the blockage, or at least the portion above water.
Photo of West Fork Mouth Bar taken on 10/4/2020.The white dots appear to be ducks.
Close comparison of these two photos shows several smaller islands beyond the mouth bar that the Army Corps removed a year ago. At the completion of the Emergency West Fork Dredging Program (2018/19), FEMA agreed to dredge 500,000 cubic yards (CY) of sediment in a 600-acre area between the mouth bar and Atascocita Point in the upper right of the photos. After dredging the 500,000 CY, the Corps increased the average depth of that area to 5.5 feet. However, within weeks, Imelda filled much of that back in.
This year, the City of Houston started excavating the above-water portion of the mouth bar. The bar is now down to width of the excavators used for mechanical dredging. To fund this effort, the City used money left over from Hurricane Harvey cleanup.
This low-level shot facing west shows just how narrow the mouth bar now is.
Biggest Part Remains Below Water
But like icebergs, most of the sediment in sand bars lies below the surface. So even when there’s nothing left for me to photograph from the air, most of the blockage will remain. Two local geologists recently measured several cross sections of the river. The river’s profile looks like this.
Compiled by RD Kissling and Tim Garfield using sonic depth finders and measurement poles.
River depth upstream near Kings Harbor and downstream near the 1960 Bridge is more than 22 feet. Between those two points (which lie about three miles apart), the deepest part of the channel is only about 6-7 feet. Not far from the main channel, however, the river gets much shallower. It’s one to three feet in most places.
In other words, at this point in the West Fork, we still have an underwater plateau – extending three miles – that continues to restrict the conveyance of the river.
The continued presence of this plateau will slow water down and trap more sediment, undermining the effectiveness of earlier efforts.
RD Kissling’s knee. Kissling, a kayaker is standing in 1-2 feet of water about three hundred yards south of the mouth bar. The homes in the background are in Atascocita Point across the river. Photo is looking west.
More Dredging Slated
Restoring the conveyance of the river after decades of deferred maintenance will require much more dredging after the above-water mouth bar is gone.
Luckily, FEMA has agreed to dredge another million cubic yards, according to Houston Mayor Pro Tem Dave Martin. State Representative Dan Huberty also secured an additional $30 million in funding in the last legislature to continue the effort.
Stephen Costello, the City’s Flood Czar, is currently working on developing a next-phase plan, but has not yet announced it.
Posted by Bob Rehak on 10/5/2020
1133 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/10/20201004-DJI_0792-2.jpg?fit=1200%2C900&ssl=19001200adminadmin2020-10-05 19:42:232020-10-05 20:11:58West Fork Mouth Bar Now Down to Width of One Excavator For Most of Its Length
The Harris County Flood Control District (HCFCD) issued its first and final report on Tropical Storm Beta today. The 24-page report found that only 25-30 homes in Harris County flooded from the storm, none in the Lake Houston Area. In most places, streams and bayous remained well within their banks. The report also says that HCFCD flood-reduction projects along Braes and Sims Bayous prevented the flooding of 930 structures. The combination of low rainfall intensities, frequent breaks in heavy rainfall, and dry grounds going into the event likely helped reduce the number of homes flooded, according to the report.
Understanding the Uniqueness of Storms
As with all such HCFCD reports, this one presents a treasure trove of statistics, graphs, charts and illustrations. Taken together, they help you understand the uniqueness of individual storms and how to compare them to each other.
Frequent Breaks in Storm Prevented More Severe Flooding
Tropical Storm Beta could have been much worse. The report says, “While Beta did produce heavy rainfall over the county, there were frequent breaks in the training rain bands.”
Overall rainfall intensities were generally in the 1.0-2.0 inch per hour range.
HCFCD final report on tropical storm beta
Most storm drains in the City of Houston are designed to handle 2″ per hour. The report continued, “The lower rainfall rates along with breaks in heavy rainfall allowed most creeks and bayous and internal drainage systems to effectively carry storm water capacities with limited flooding.”
2- to 10-Year Rains in Most Harder-Hit Areas
In most of the harder-hit areas, the storm dropped between 2- and 10-year rains. Those included Clear Creek, Brays Bayou, Keegans Bayou, Willow Waterhole, Buffalo Bayou, White Oak Bayou and Cypress Creek. One place along Sims Bayou recorded a 50-year rain. All other Harris County watersheds had generally less than a 50% (2-yr) rainfall exceedance probability, says the report. Those rainfall exceedance probabilities correspond to new Atlas-14 rates adopted after Harvey.
Intense Short-Duration Rains Cause Most Street Flooding
House flooding in Harris County correlates strongly to the intensity of short duration rainfall rates. In Tropical Storm Beta, short duration rainfall rates generally fell below intensities that lead to widespread and significant house flooding from:
Overwhelming capacity of primary drainage systems or…
Exceeding capacities of bayous and creeks.
The following chart compares the maximum rainfall amounts recorded in Harris County from Tropical Storm Imelda, Hurricane Harvey, Tropical Storm Allison, and Tropical Storm Beta for various time periods.
From page 3 of HCFCD’s Final Report on Tropical Storm Beta.
The chart above compares the maximum rainfall amounts recorded in Harris County from Tropical Storm Imelda, Hurricane Harvey, Tropical Storm Allison, and Tropical Storm Beta for various time periods.
For the 1-hr rainfall rate, Beta was nearly 50% lower than Imelda, Allison, and Harvey and nearly 8-10 inches lower for the 3-hr rainfall rates.
HCFCD Final Report on Beta
Beta Rates Lower than Other Recent Major Storms
As the chart above shows, rainfall rates associated with Tropical Storm Beta fell significantly below other recent tropical storms that impacted Harris County. The lower rainfall rates were likely a function of a dry air mass wrapping into the circulation, and a general lack of organized and persistent thunderstorm activity.
Beta’s short duration rainfall rates remained slow enough that drainage systems could remain effective. Additionally, dry grounds leading into the event allowed the first few inches of rainfall to be absorbed, helping to reduce run-off.
Jeff Lindner, Harris County Meteorologist
Dramatic NW to SE Rainfall Gradient
The maximum rainfall over 48 hours shows a dramatic gradient aligning from northwest to southeast. As you can see from the iso-map below, people in the Lake Houston Area received less than a third of the rainfall that people received on the southwest side of Houston.
Posted by Bob Rehak on 10/5/2020based on information from Harris County Flood Control
1133 Days after Hurricane Harvey and 382 after Imelda
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/10/Screen-Shot-2020-10-05-at-2.22.51-PM.png?fit=1064%2C572&ssl=15721064adminadmin2020-10-05 15:10:032020-10-05 15:24:08Final HCFCD Report on Tropical Storm Beta Finds Only 25-30 Homes Flooded
Delta Explodes into Hurricane; Should Become Major Hurricane by Wednesday; Track Shifts Slightly West
Twenty-four hours ago, Hurricane Delta was simply potential tropical cyclone #26. As of 8 P.M. EDT today, the National Hurricane Center indicated #26 had progressed from tropical depression to tropical storm to hurricane in 24 hours. By tomorrow night, Delta should become a major hurricane as it crosses the resort areas on the northeastern tip of the Yucatan. However, the NHC also predicts that the storm will de-intensify before it makes landfall somewhere between East Texas and the Florida Panhandle on Friday.
Winds Could Increase from 75 to 120 mph
Low wind sheer and warm waters in the northwest Caribbean will allow rapid strengthening over the next 24 to 36 hours. The storm already has sustained winds of 75 mph. NHC gives a better than 50 percent chance of a 35-40 kt increase in wind speed over the next 24 hours. That’s roughly another 40 to 45 mph.
Track Shifts Slightly West
The NHC has shifted the track envelope westward over today, bringing the storm closer to Houston, though we are still slightly outside the cone.
Tropical Storm Force Winds Currently Extend 70 miles From Center
NHC expects additional rapid strengthening during the next day or so. Delta, they say, should become a major hurricane when it nears the Yucatan Peninsula. Hurricane-force winds extend outward up to 15 miles (25 km) from the center and tropical-storm-force winds extend up to 70 miles (110 km) from the center.
Louisiana to Western Florida Faces Largest Danger
NHC advises, “Delta is forecast to approach the northern Gulf Coast late this week as a hurricane. While there is large uncertainty in the track and intensity forecasts, there is an increasing risk of dangerous storm surge, wind, and rainfall hazards along the coast from Louisiana to the western Florida Panhandle beginning Thursday night or Friday. Residents in these areas should ensure they have their hurricane plan in place and monitor updates to the forecast of Delta.”
Impact to Texas Coast?
Jeff Lindner, Harris County Meteorologist, says, “Swells will be increasing over the northwest Gulf of Mexico by mid week with heights increasing into the 5-10 foot range by Wednesday. This will result in increasing tides along the upper TX coast. Current projections indicate 1.0-1.5 feet above normal levels at times of high tides Thursday and Friday. This is subject to change based on the intensity and wind field of Delta over the central and NW Gulf late this week.”
While SE TX is currently outside the “error cone” and direct impacts appear unlikely, Lindner says that its important to closely monitor forecasts for any changes in the track.
Posted by Bob Rehak at 9PM on Monday, 10/5/2020 based on data from the NHC and HCFCD
1133 Days since Hurricane Harvey
West Fork Mouth Bar Now Down to Width of One Excavator For Most of Its Length
Aerial photos of the West Fork Mouth Bar show that the above-water portion on this once-massive sand bar is now down to the width of one excavator for most of its length. A mouth bar is a sand bar where the mouth of a river or stream meets a standing body of water, such as Lake Houston. As water slows when it reaches the standing water, sediment carried downstream drops out of suspension.
The Before Shot
The first photo below shows the West Fork Mouth Bar immediately after Harvey and before any remediation work took place.
At that point in time, the mouth bar extended five feet above water in places. It was 3/4 of a mile wide and a half mile from the northernmost part to the small island in the channel south of the bar. But the part you can’t see, below water, is even bigger.
Today
I took the shot below on Sunday night, 10/4/2020. While the camera position and lens perspective are slightly different, they are close enough to show the progress made in removing the blockage, or at least the portion above water.
Close comparison of these two photos shows several smaller islands beyond the mouth bar that the Army Corps removed a year ago. At the completion of the Emergency West Fork Dredging Program (2018/19), FEMA agreed to dredge 500,000 cubic yards (CY) of sediment in a 600-acre area between the mouth bar and Atascocita Point in the upper right of the photos. After dredging the 500,000 CY, the Corps increased the average depth of that area to 5.5 feet. However, within weeks, Imelda filled much of that back in.
This year, the City of Houston started excavating the above-water portion of the mouth bar. The bar is now down to width of the excavators used for mechanical dredging. To fund this effort, the City used money left over from Hurricane Harvey cleanup.
Biggest Part Remains Below Water
But like icebergs, most of the sediment in sand bars lies below the surface. So even when there’s nothing left for me to photograph from the air, most of the blockage will remain. Two local geologists recently measured several cross sections of the river. The river’s profile looks like this.
River depth upstream near Kings Harbor and downstream near the 1960 Bridge is more than 22 feet. Between those two points (which lie about three miles apart), the deepest part of the channel is only about 6-7 feet. Not far from the main channel, however, the river gets much shallower. It’s one to three feet in most places.
The continued presence of this plateau will slow water down and trap more sediment, undermining the effectiveness of earlier efforts.
More Dredging Slated
Luckily, FEMA has agreed to dredge another million cubic yards, according to Houston Mayor Pro Tem Dave Martin. State Representative Dan Huberty also secured an additional $30 million in funding in the last legislature to continue the effort.
Stephen Costello, the City’s Flood Czar, is currently working on developing a next-phase plan, but has not yet announced it.
Posted by Bob Rehak on 10/5/2020
1133 Days since Hurricane Harvey
Final HCFCD Report on Tropical Storm Beta Finds Only 25-30 Homes Flooded
The Harris County Flood Control District (HCFCD) issued its first and final report on Tropical Storm Beta today. The 24-page report found that only 25-30 homes in Harris County flooded from the storm, none in the Lake Houston Area. In most places, streams and bayous remained well within their banks. The report also says that HCFCD flood-reduction projects along Braes and Sims Bayous prevented the flooding of 930 structures. The combination of low rainfall intensities, frequent breaks in heavy rainfall, and dry grounds going into the event likely helped reduce the number of homes flooded, according to the report.
Understanding the Uniqueness of Storms
As with all such HCFCD reports, this one presents a treasure trove of statistics, graphs, charts and illustrations. Taken together, they help you understand the uniqueness of individual storms and how to compare them to each other.
Frequent Breaks in Storm Prevented More Severe Flooding
Tropical Storm Beta could have been much worse. The report says, “While Beta did produce heavy rainfall over the county, there were frequent breaks in the training rain bands.”
Most storm drains in the City of Houston are designed to handle 2″ per hour. The report continued, “The lower rainfall rates along with breaks in heavy rainfall allowed most creeks and bayous and internal drainage systems to effectively carry storm water capacities with limited flooding.”
2- to 10-Year Rains in Most Harder-Hit Areas
In most of the harder-hit areas, the storm dropped between 2- and 10-year rains. Those included Clear Creek, Brays Bayou, Keegans Bayou, Willow Waterhole, Buffalo Bayou, White Oak Bayou and Cypress Creek. One place along Sims Bayou recorded a 50-year rain. All other Harris County watersheds had generally less than a 50% (2-yr) rainfall exceedance probability, says the report. Those rainfall exceedance probabilities correspond to new Atlas-14 rates adopted after Harvey.
Intense Short-Duration Rains Cause Most Street Flooding
House flooding in Harris County correlates strongly to the intensity of short duration rainfall rates. In Tropical Storm Beta, short duration rainfall rates generally fell below intensities that lead to widespread and significant house flooding from:
The following chart compares the maximum rainfall amounts recorded in Harris County from Tropical Storm Imelda, Hurricane Harvey, Tropical Storm Allison, and Tropical Storm Beta for various time periods.
The chart above compares the maximum rainfall amounts recorded in Harris County from Tropical Storm Imelda, Hurricane Harvey, Tropical Storm Allison, and Tropical Storm Beta for various time periods.
Beta Rates Lower than Other Recent Major Storms
As the chart above shows, rainfall rates associated with Tropical Storm Beta fell significantly below other recent tropical storms that impacted Harris County. The lower rainfall rates were likely a function of a dry air mass wrapping into the circulation, and a general lack of organized and persistent thunderstorm activity.
Dramatic NW to SE Rainfall Gradient
The maximum rainfall over 48 hours shows a dramatic gradient aligning from northwest to southeast. As you can see from the iso-map below, people in the Lake Houston Area received less than a third of the rainfall that people received on the southwest side of Houston.
To see the entire 24-page report, click here. For easy future reference, this report can also be found under the Major Storms Tab on the Reports page.
Posted by Bob Rehak on 10/5/2020 based on information from Harris County Flood Control
1133 Days after Hurricane Harvey and 382 after Imelda