On August 1, the City of Houston Public Works Department, the San Jacinto River Authority (SJRA) and the Coastal Water Authority (CWA) plan to begin lowering the level of Lake Conroe as part of a joint operations plan to mitigate flooding threats during the peak of hurricane season. The plan calls for lowering Lake Conroe gradually through small releases – about an inch a day – until the lake level reaches 199 msl (mean feet above sea level).
Intent of gradual lowering of Lake Conroe is to avoid another 79,000 cubic-feet-per-second release rate as we experienced during Harvey. Until normal flow is restored to the West Fork, Lake Conroe will be lowered temporarily and seasonally to mitigate flood risk.
Lake Conroe to Be Lowered 2 Feet Through September
This initial lowering will last through the end of September to create additional storage in Lake Conroe which could delay releases and minimize release rates during a storm, thereby providing a buffer against flooding for residents who live downstream of the dam.
The next lowering would occur during the peak of the spring rainy season – from April 1 – May 31, 2019. However, that lowering would only be by a foot – to 200 msl, because the rain threat is usually lower in spring.
Only Until Dredging Restores River’s Flow
The joint operations plan calls for continuing to lower Lake Conroe seasonally in this manner while the U.S. Army Corps of Engineers dredges the West Fork of the San Jacinto to restore flow.
Hurricane Harvey deposited tremendous amounts of silt in the West Fork which physically changed the river’s ability to safely pass water during storms. Hence, the dredging.
Phase-One Dredging Has Already Started
Phase one will go from River Grove Park to the West Lake Houston Parkway bridge. Great Lakes, the contractor hired by the Corps, has 269 more days to complete the initial phase.
Mobilization and demobilization comprise 25 percent of the total phase one project costs (approximately $18 million out of almost $70 million). Having phase two ready to start before phase one ends could save that money, creating extra value for taxpayers and enabling even more dredging, say for instance, on the East Fork.
Temporary Lake Conroe Lowering Could Last Up to 3 Years
The City, SJRA, and CWA will continue the seasonal lowerings for up to three three years. They will monitor progress of the dredging and annually re-evaluate the need to lower Lake Conroe. If the river’s flow is restored before three years, the temporary lowering would cease.
Lakes will Operate under Two Different Strategies
LAKE CONROE
Lake Conroe is located upstream from Lake Houston. Large pre-releases immediately before a storm run the risk of pushing water into Lake Houston at a rate that could flood residents. Therefore, the SJRA will release at a much more gradual, controlled rate and maintain the lower level until the largest flood threat passes.
LAKE HOUSTON
Lake Houston, as the lowest lake on the river system, can pre-release more safely. Therefore CWA will pre-release from Lake Houston if the National Weather Service predicts more than 3 inches of rain within the San Jacinto River basin in a 48-hour period. Coastal Water Authority will lower Lake Houston to 41.5 feet from its normal elevation of 42.5 feet.
To track lake levels visit:
Lake Conroe – www.sjra.net
Lake Houston – www.coastalwaterauthority.org
4 Million People Depend on City for Water
Lake Conroe and Lake Houston comprise two of the largest parts of the City’s drinking water system. More than 4 million Houstonians and residents of the greater Houston region rely on water provided by the City.
Posted by Bob Rehak on July 30, 2018
335 Days since Hurricane Harvey
00adminadmin2018-07-30 22:49:512020-01-17 10:03:56Seasonal Lowering of Lake Conroe Begins August 1
When considering property tax implications of the proposed $2.5 billion flood bond, start with how much you currently pay in Harris County Flood Control District (HCFCD) taxes. Hint: It’s very little.
Only about 1.4% of Typical Property Tax Bill Currently Goes to Flood Control
Only about 1.4% of the average annual property tax bill now goes to Flood Control. The rest funds schools, cities, hospitals, law enforcement, etc. How much you currently pay each year in flood control taxes depends on your home’s value and your exemptions. See some representative costs below.
What homes assessed at representative price points will pay in additional taxes if the Harris County Flood Control Bond passes.
Amount Will Vary Depending on Age, Assessment and Exemptions
If your home is assessed at $200,000 and you are under 65, you pay only $45 annually for flood control. If over 65 in that same home, you pay no flood control taxes.
In a worst-case scenario, Harris County says the flood-control portionof your taxes would double. Would doubling one of the numbers above create a hardship for you? Or would it help you sleep better?
Remember, any increase applies only to the flood control portion of your tax bill, not the entire bill.
Less than Cost of Flood Insurance
Any increase would be gradual. Bonds are only sold when projects are ready to start. Harris County expects no increase at all until 2020 at the earliest.
Flood Control improvements cost much less than flood insurance. And unlike flood insurance, they might actually prevent your home from being damaged.
Protecting Home and Community Values
Once implemented, the flood mitigation measures in the bond package will help make our entire community more resistant to flooding. That’s important. It helps protect your home’s value, your schools, businesses, roads, bridges and other infrastructure. That helps keep your community growing and makes it attractive for people looking to relocate. In the long run, rising home values will pay you back many times over for your investment in flood control. So send a signal to the world that we’re willing to invest in our future.
How to Check Your Current Assessed Value
To see how much you pay right now, go to hcad.org, click on “Property Search”, then “Real Property” followed by “Search by Address.”
Posted by Bill Fowler on July 29, 2018
334 Days since Hurricane Harvey
00adminadmin2018-07-27 22:21:572018-07-29 10:26:43How Much Would the Flood Bond Cost You?
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.
They compiled this fascinating 28-page report about the mouth bar, which I helped them edit. It explains how the river is changing, why it’s crucial to remove the mouth bar, and what will likely happen if we don’t.
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
Seasonal Lowering of Lake Conroe Begins August 1
On August 1, the City of Houston Public Works Department, the San Jacinto River Authority (SJRA) and the Coastal Water Authority (CWA) plan to begin lowering the level of Lake Conroe as part of a joint operations plan to mitigate flooding threats during the peak of hurricane season. The plan calls for lowering Lake Conroe gradually through small releases – about an inch a day – until the lake level reaches 199 msl (mean feet above sea level).
Intent of gradual lowering of Lake Conroe is to avoid another 79,000 cubic-feet-per-second release rate as we experienced during Harvey. Until normal flow is restored to the West Fork, Lake Conroe will be lowered temporarily and seasonally to mitigate flood risk.
Lake Conroe to Be Lowered 2 Feet Through September
This initial lowering will last through the end of September to create additional storage in Lake Conroe which could delay releases and minimize release rates during a storm, thereby providing a buffer against flooding for residents who live downstream of the dam.
The next lowering would occur during the peak of the spring rainy season – from April 1 – May 31, 2019. However, that lowering would only be by a foot – to 200 msl, because the rain threat is usually lower in spring.
Only Until Dredging Restores River’s Flow
The joint operations plan calls for continuing to lower Lake Conroe seasonally in this manner while the U.S. Army Corps of Engineers dredges the West Fork of the San Jacinto to restore flow.
Hurricane Harvey deposited tremendous amounts of silt in the West Fork which physically changed the river’s ability to safely pass water during storms. Hence, the dredging.
Phase-One Dredging Has Already Started
Phase one will go from River Grove Park to the West Lake Houston Parkway bridge. Great Lakes, the contractor hired by the Corps, has 269 more days to complete the initial phase.
Phase-Two Still Needs Funding
The total project could take longer. Community leaders are now working furiously to arrange funding to dredge the remainder of the west fork, including the mouth bar.
Mobilization and demobilization comprise 25 percent of the total phase one project costs (approximately $18 million out of almost $70 million). Having phase two ready to start before phase one ends could save that money, creating extra value for taxpayers and enabling even more dredging, say for instance, on the East Fork.
Temporary Lake Conroe Lowering Could Last Up to 3 Years
The City, SJRA, and CWA will continue the seasonal lowerings for up to three three years. They will monitor progress of the dredging and annually re-evaluate the need to lower Lake Conroe. If the river’s flow is restored before three years, the temporary lowering would cease.
Lakes will Operate under Two Different Strategies
LAKE CONROE
Lake Conroe is located upstream from Lake Houston. Large pre-releases immediately before a storm run the risk of pushing water into Lake Houston at a rate that could flood residents. Therefore, the SJRA will release at a much more gradual, controlled rate and maintain the lower level until the largest flood threat passes.
LAKE HOUSTON
Lake Houston, as the lowest lake on the river system, can pre-release more safely. Therefore CWA will pre-release from Lake Houston if the National Weather Service predicts more than 3 inches of rain within the San Jacinto River basin in a 48-hour period. Coastal Water Authority will lower Lake Houston to 41.5 feet from its normal elevation of 42.5 feet.
To track lake levels visit:
4 Million People Depend on City for Water
Lake Conroe and Lake Houston comprise two of the largest parts of the City’s drinking water system. More than 4 million Houstonians and residents of the greater Houston region rely on water provided by the City.
Posted by Bob Rehak on July 30, 2018
335 Days since Hurricane Harvey
How Much Would the Flood Bond Cost You?
When considering property tax implications of the proposed $2.5 billion flood bond, start with how much you currently pay in Harris County Flood Control District (HCFCD) taxes. Hint: It’s very little.
Only about 1.4% of Typical Property Tax Bill Currently Goes to Flood Control
Only about 1.4% of the average annual property tax bill now goes to Flood Control. The rest funds schools, cities, hospitals, law enforcement, etc. How much you currently pay each year in flood control taxes depends on your home’s value and your exemptions. See some representative costs below.
What homes assessed at representative price points will pay in additional taxes if the Harris County Flood Control Bond passes.
Amount Will Vary Depending on Age, Assessment and Exemptions
If your home is assessed at $200,000 and you are under 65, you pay only $45 annually for flood control. If over 65 in that same home, you pay no flood control taxes.
In a worst-case scenario, Harris County says the flood-control portionof your taxes would double. Would doubling one of the numbers above create a hardship for you? Or would it help you sleep better?
Less than Cost of Flood Insurance
Any increase would be gradual. Bonds are only sold when projects are ready to start. Harris County expects no increase at all until 2020 at the earliest.
Flood Control improvements cost much less than flood insurance. And unlike flood insurance, they might actually prevent your home from being damaged.
Protecting Home and Community Values
Once implemented, the flood mitigation measures in the bond package will help make our entire community more resistant to flooding. That’s important. It helps protect your home’s value, your schools, businesses, roads, bridges and other infrastructure. That helps keep your community growing and makes it attractive for people looking to relocate. In the long run, rising home values will pay you back many times over for your investment in flood control. So send a signal to the world that we’re willing to invest in our future.
How to Check Your Current Assessed Value
To see how much you pay right now, go to hcad.org, click on “Property Search”, then “Real Property” followed by “Search by Address.”
Posted by Bill Fowler on July 29, 2018
334 Days since Hurricane Harvey
Why We Must Remove Mouth Bar on West Fork of San Jacinto
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.
They compiled this fascinating 28-page report about the mouth bar, which I helped them edit. It explains how the river is changing, why it’s crucial to remove the mouth bar, and what will likely happen if we don’t.
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:
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.
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).
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.
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