As of 4 PM Thursday, Delta has restrengthened into a category 3 hurricane with winds of 115 mph. One day before Delta makes landfall, it now appears that once again, the Lake Houston Area will miss the brunt of a vicious storm. Unfortunately, for the poor folks in Louisiana, it appears that Delta will take the same track that Laura did last month and ravage them once again.
Folks east of High Island, TX remain under a hurricane warning. Those between Sargent, TX and High Island are under a tropical storm warning. A storm surge warning remains in effect for everyone between High Island and Mississippi.
Warnings mean that conditions are expected within the warning area, usually within 36 hours.
Projected Track; Tropical Storm Force Winds Extend Out 160 miles
Forecast models are now strongly in agreement on the projected track. That still doesn’t mean the Lake Houston Area is in the clear. Hurricane-force winds extend outward up to 35 miles from the center and tropical-storm-force winds extend outward up to 160 miles, according to Harris County Meteorologist Jeff Lindner.
Lake Houston Area Impacts
NHC now predicts we have a 60-70% chance of experiencing tropical-storm-force winds.
They most likely will arrive tomorrow morning around 8 A.M. Delta is moving NNW at around 15 miles per hour. According to Lindner, “Tropical storm force winds will be possible in the TS warning area, although this will be heavily dependent on the expansion of the wind field. Chambers and southern Liberty Counties have the greater risk of sustained tropical storm force winds. We could see sustained tropical storm force winds in and around Galveston Bay on Friday and over southeast Harris, Galveston, and coastal Brazoria Counties.
NHC predicts the storm will weaken into a tropical depression within 36 hours after coming ashore.
The eastern part of Houston could see anywhere between one and four inches of rain, with the higher totals farther east. Louisiana will likely see 6-10 inches.
Still, there is only a marginal (<5%) to slight (<10%) risk of flash flooding.
Storm Surge Warnings
One of the most serious threats: storm surge. NHC predicts water up to 11 feet above ground in the area around Vermillion Bay.
Posted By Bob Rehak on 10/8/2020 at 5:15 PM based on data from NHC and HCFCD
1136 Days after Hurricane Harvey and 385 Days after Imelda
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/10/Screenshot-2020-10-08-at-2.56.39-PM-scaled.jpg?fit=1183%2C2560&ssl=125601183adminadmin2020-10-08 17:23:202020-10-08 17:30:54Hurricane Delta Tracking East; Back up to Cat 3, But Houston Out of Cone
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, 10/5/2020based 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
Two more tropical systems are heading into the Gulf of Mexico this week. The National Hurricane Center (NHC) predicts the first, Tropical Storm Gamma, will hook around the Yucatan and then turn north Wednesday into Thursday. It should be in the central Bay of Campeche by Friday, still headed north.
The NHC predicts the second, potential tropical cyclone #26, will intensify into a hurricane and reach the central Gulf Coast of the U.S. by Friday. While a wide range of uncertainty exists regarding its track, dangerous storm surge and coastal flooding from Louisiana to the Florida Panhandle is almost a certainty, according the the NHC. Increasing swells and elevated tides will be possible along the Texas coast from mid- into late-week given both systems over the Gulf of Mexico, according to Jeff Lindner, Harris County meteorologist.
Lindner also predicts Delta could become a Cat 2 or even a Cat 3 hurricane before reaching land.
No Impact Predicted for Texas At This Time
At this time (Sunday night, 10/4/2020 at 9:45PM), Lindner also feels that Houston area should feel no direct impacts from either TS Gamma or what will likely become TS Delta.
Posted by Bob Rehak on 10/4/2020 at 9:45 PM based on data from HCFCD and the NHC
1132 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/10/233230_5day_cone_no_line_and_wind.png?fit=897%2C736&ssl=1736897adminadmin2020-10-04 22:04:362020-10-04 22:04:48Two More Tropical Systems Heading Into Gulf This Week
The U.S. Army Corps of Engineers originally solicited bids to dredge the West Fork of the San Jacinto from 59 to Lake Houston, a distance of 8 miles. At some point in the project, the Corps limited the scope to 2.1 miles – from River Grove Park to the West Lake Houston Parkway bridge – for reasons never made clear. Perhaps they ran out of money when they had to double the volume they were dredging in that 2.1 miles. Regardless, that meant leaving a huge sandbar in place at the mouth of the river (see below).
I have been concerned about that bar ever since they excluded it from the scope. I wasn’t the only one. Two retired geologists, Tim Garfield and R.D. Kissling, approached me after my post about reduced scope. They have more than 50 years of experience with one of the world’s most successful oil companies. Both are experts in river morphology and sedimentation.
The goal of this presentation was to get the Corps to expand the scope of their current dredging project to include the bar. Why? Approximately half of all the damage that occurred in Kingwood occurred BEYOND where the Corp intends to stop dredging. If not removed, everything behind the mouth bar for miles upstream will be at greater risk of flooding.
Major Concerns From a Geologist’s Perspective
If this blockage is left in place, it will, say Garfield and Kissling:
Cause the river to run UPHILL
Create, in effect, a partial dam
Slow water down, back it up and elevate the water surface
Increase flooding upstream
Increase the rate of sedimentation behind it
Cause the river to escape its banks, flood neighborhoods and damage or destroy infrastructure
How the River Is Changing
Since the late 1970s, a delta has been forming within the river and advancing toward where the river meets the lake. You can see the 2-mile advance most clearly in this summary slide that shows Kingwood in 1977 and 2017.
Evolution of mouth bar over 40 years. The full presentation contains many intermediate images.
When Friendswood designed Kingwood’s drainage, it was based on a different reality. Note, for instance, what happened east of the West Lake Houston Parkway Bridge. A huge area has filled in, reducing the conveyance of the river.
The chart below shows the increasing rate of change in the Stream Mouth Bar (SMB) at the right in the photo above (the area outlined in white with the red arrow pointing to it).
Sudden exponential growth in mouth bar volume tells geologists that it has reached critical mass and is likely contributing in a major way to upstream flooding.
How Our Mouth Bar Contributes to Upstream Flooding
This next series of slides shows how and why the West Fork mouth bar affects flooding.
Before the Lake Houston Dam was built, water in the river dropped steadily in elevation from the site of today’s Grand Parkway all the way to the coast.
Since the construction of the Lake Houston Dam, water continues to drop to US59, but then it levels out. That’s because the dam backs up water that far.
A huge mouth bar grew up where the river enters the lake. As water slowed down and spread out, it deposits sediment. When the river is flowing at normal levels, water can find its way around the blockage without threatening neighborhoods.
However, during floods, the mouth bar acts as a partial dam. It creates a hydraulic jump that begins to back water up behind it. Note how the orange bar is higher on the left than on the right, relative to the blue line. That’s because the stream mouth bar increases the height of water behind it during a flood.
If the mouth bar were removed, water would no longer back up behind it. The river could flow freely in a flood. The dotted line represents an estimate of how much a flood like Harvey could be lowered. If the reduction were four to six feet, that could make the difference between major and minor flooding.
In this profile, the horizontal scale is less compressed than in the charts above it, so you can visualize more easily how water is forced to flow uphill as it approaches the mouth bar. This forces water to flow uphill and the water surface to elevate behind the mouth bar, contributing to upstream flooding.
Options Going Forward
Ignoring the mouth bar and hoping it will go away is not an option.
It has nearly doubled in size in the last three years. It will force the river to flood more frequently and more extensively, causing more damage to houses and infrastructure.
I suspect that the reason the Corps did not handle this in the first place is because they were constrained by budget. So removing the mouth bar as part of a change order is not an option either.
It will likely cost far more to remove the mouth bar than it does to clear the 2.1 miles upstream.
That leaves two options recommended by the Army Corps’ Deputy District Engineer for Programs and Project Management, Dr. Ed Russo (plus another that he didn’t recommend).
Option 1: Russo helped draft a proposal request for consideration under Section 7001 of the Water Resources and Reform Development Act of 2014. The proposal requires a local, county, or state agency to put up a match for federal funds. Deadline is August 20. If approved by Congress this fall, the mouth bar could potentially be removed while Great Lakes still has dredging equipment on the river, saving the cost of another mobilization.
Option 2: Similar to 1, but without cost sharing. A partnership of local, county, state, or federal agencies can hire the Corps to be their public engineer and constructor for the project under an Interagency Agreement . This requires 100% funding by the Federal, state, county, or local agency. There is no cost share. Hmmmm. County Bond Referendum? The State’s rainy day fund? Lots of possibilities. But they would probably take longer to work out.
Option 3: Go it alone.
Benefits of Removing the Mouth Bar
The Lower West Fork delta of the San Jacinto River is advancing development in size and shape. The West Fork mouth bar and surrounding shoal sediments are constraining in-bank flow conveyance capacity.
With no action to restore flow conveyance capacity within the river’s banks, the evolving conditions will cause the river to rise out of its banks and extensively flood properties and critical infrastructure in the region. If addressed, flood risks to developments will be reduced and the river will have the conveyance capacity to pass flood flows and flush sediment that would otherwise reduce conveyance capacity.
Removing the mouth bar would reduce flood damages to properties regionally and provide for increased resilience to flooding of properties, transportation systems, water treatment systems, public/private utilities, emergency response facilities, petrochemical industries, and other critical infrastructure, in the West Fork, San Jacinto River Watershed, Harris, Montgomery, and Liberty Counties,TX, on the order of $200 Billion.
Given that petrochemical industries in the region produce a significant amount of the Nation’s petroleum based energy products, reducing flood risks of these plants and its workers who reside in flood-prone areas, and providing for greater resiliency, is a National security benefit. The environmental benefit of providing for this project is reduced risks of water treatment plant and chemical spills due to flooding, which is a threat to human and environmental health and safety. The non-monetary benefits would include reduce risks to loss of life due to regional flooding, especially to residents with insufficient means.
Posted by Bob Rehak, R.D. Kissling and Tim Garfield on July 27, 2018
332 Days since Hurricane Harvey
00adminadmin2018-07-27 17:56:072018-07-28 07:14:48Why We Must Remove Mouth Bar on West Fork of San Jacinto