Tag Archive for: Harvey

By Itself, Lake Conroe Discharge During Harvey Among Top Ten West Fork Floods of All Time

The roughly 80,000 cubic feet per second (CFS) Lake Conroe discharged at the peak of Harvey would have created the ninth largest flood in West Fork History – all by itself. Only eight floods ever had higher “discharge” rates AND those all included floodwaters from other tributaries, such as Lake Creek, Spring Creek, Cypress Creek and numerous drainage ditches.

Discharge is the volume of water flowing past a point on a stream. Discharge from a dam would be the volume flowing past the gates.

The discharge during Harvey is important because residents fighting the seasonal lowering of Lake Conroe claim the impact of the release on Humble and Kingwood was insignificant.

Question I Asked Flood Control

So I asked Jeff Lindner, Harris County Flood Control meteorologist, this simple question. “Assuming not a drop of rain fell in any other of the West Fork tributaries, where would that 80,000 CFS have ranked among the history of West Fork floods?” I then asked him to base his analysis on the West Fork gage at US59. It combines water from ALL upstream West Fork tributaries. It’s also the closest gage in continuous operation to the highly populated Humble/Kingwood corridor. That’s where the vast majority of Lake Houston Area damage occurred during Harvey.

Only eight floods have ever exceeded 80,000 CFS at US59.

They occurred on:

  • 8/28/17 (Harvey)
  • 10/18/94 (Previous Record Flood)
  • 11/26/40
  • 5/31/29
  • 5/29/16 (Memorial Day)
  • 11/15/98
  • 5/7/35
  • 4/21/16 (Tax Day)

Note: three of these events happened before the construction of Lake Conroe in 1973. All since the advent of Lake Conroe flooded West Fork structures.

One Statistic Addresses Host of Issues

This observation (ninth largest flood by itself) addresses a host of issues raised by Lake Conroe people about lowering the lake seasonally to create a buffer against downstream flooding. They contend that:

  • In the grand scheme of things, the Lake Conroe release during Harvey had an insignificant impact on flooding in the Humble/Kingwood area.
  • Kingwood always floods.
  • Imelda proves that Kingwood will flood even when Conroe is not releasing water.
  • There’s no need to create extra storage capacity to offset future floods.

What Records Really Show

On the contrary:

Will Two Feet Matter?

Lowering Lake Conroe two feet in advance of another Harvey will probably not make much of a difference. Likewise, lowering it two feet in advance of 1-inch rain would be unnecessary. The real value happens somewhere between those extremes in a 10-, 25-, 50- or perhaps even a 100-year storm. Somewhere along that spectrum, we will get enough rain to perhaps flood homes, but we’ll also have enough extra lake capacity to avoid actually flooding them.

We just don’t know where that point is right now. Jing Chen, the engineer with Harris County Flood Control managing the San Jacinto River Basin Study says that project will not be far enough along to model those scenarios until August of this year.

However, the SJRA feels the lower lake levels did help avoid flooding between Humble and Kingwood in May of last year. I concur. It’s also possible that the two foot lowering might create enough of a buffer to have avoided flooding many homes along the West Fork during the Tax and Memorial Day floods in 2016. Perhaps it wouldn’t have saved them all. But it might have avoided flooding many at the periphery of a flood.

Increasing Upstream Detention Capacity: A Proven Flood Mitigation Strategy

According to Matt Zeve, Deputy Executive Director of Harris County Flood Control, holding water upstream is a proven flood mitigation strategy. Engineers in the Houston area created upstream detention more than 80 years ago with the Barker and Addicks reservoirs. Braes Bayou now has five different detention areas; White Oak Bayou has five with another under construction.

Such detention areas collect water during a storm and then release it slowly after a flood passes.

The extra storage capacity created by lowering Lake Conroe 1-2 feet works the same way. The idea: to reduce the amount and/or rate of water released during a flood to help avoid downstream property damage.

SJRA Mission and Lake Conroe History Includes Flood Prevention

The enabling legislation of the SJRA mentions flood prevention three times. Moreover, the area now occupied by Lake Conroe was considered for floodwater detention as early as 1957, as this Master Plan for the SJRA that year shows – i.e., on the map below. Many of these proposed lakes/reservoirs serve a dual purpose according to Zeve. They help prevent floods AND supply water.

Page 29 of SJRA Master Plan from 1957

This map puts to rest another rumor spread by the Lake Conroe Association. They claim Lake Conroe was never conceived as a flood control reservoir; it is strictly a water supply reservoir. See the discussion of flood control starting on page 16 of the 1957 Master Plan. Then on page 27, see Exhibit A.

It shows the SJRA considered building 20 dams that year.

So far it has built only one: Lake Conroe.

Therefore, Lake Conroe is currently the only way we have to mitigate flooding until we put other mitigation measures in place.

Posted by Bob Rehak on 1/23/2020

877 Days since Hurricane Harvey

Note: A reader’s question on Facebook prompted this post. But I can’t find his name now. My apologies. No offense intended.

From Drought to Floods: The Decade in Review

Jeff Lindner, the Harris County Flood Control District Meteorologist compiled this Decade in Review. After a very dry start, the decade ended incredibly wet. We started with five years of below normal rainfall (2010-2014). Then rains and floods returned in 2015 and continued through 2019. For the period from 2010-2014, the rainfall DEFICIT for BUSH IAH was -56.70 inches. For the period from 2015-2019, the rainfall SURPLUS was +69.78 inches.

Five Deficit Years…

2010: 42.72 (-7.07)

2011: 24.57 (-25.2)

2012: 43.32 (-7.45)

2013: 38.84 (-10.93)

2014: 43.72 (-6.05)

Followed by Five Surplus Years

2015: 70.03 (+20.26)

2016: 60.96 (+11.19)

2017: 79.69 (+29.92)

2018: 56.02 (+6.25)

2019: 51.93 (+2.16)

The decade featured one of the most significant droughts since the 1950’s across the state of Texas and a series of floods that rivals any period of flooding ever experienced in this state.

Jeff Lindner, Harris County Flood Control Meteorologist

1. Hurricane Harvey (2017)

Harvey made landfall at Port Aransas on August 27, 2017 at 10:00 pm as a category 4 hurricane with 130mph winds producing extensive wind damage across portions of the Texas coastal bend. A maximum wind gust of 132mph was recorded at Port Aransas and 118mph at Copano Bay. Harvey would then meander slowly east-northeast across portions of southeast Texas and the extreme northwest Gulf of Mexico producing record breaking rainfall and flooding.

A maximum total rainfall of 60.58 inches was recorded at Nederland, TX with over 10,000 square miles receiving over 35 inches of rainfall.

Across Harris County, on average 33.7 inches of rainfall occurred, resulting in record flooding along many of the bayous and creeks. In additional inflows into Addicks and Barker Reservoirs resulted in record pool elevations (exceeded Tax Day by 6.0 feet) in both reservoirs and significant flooding of structures located within the flood pools. Water flowed around the north end spillway of Addicks for the first time since the completion of the dams in the 1940’s.  In Harris County alone over 154,000 homes were flooded and statewide over 250,000 homes were damaged from either flooding or wind. An estimated 500,000 vehicles were damaged or destroyed.

In the counties of Jefferson, Orange, Hardin, and Tyler upwards of 110,000 structures were flooded which is about 33% of the total number of structures in these four counties.

The highway 96 bridge over Village Creek near Silsbee, TX was completely washed away. In Fort Bend County over 200,000 residents were asked to evacuate due to flooding from Barker Reservoir, the Brazos River, and local drainage issues with some 8,700 homes being flooded. Over 9,000 homes were flooded in Brazoria County and over 7,000 in Galveston County. Many of the creeks, bayous, and rivers in southeast Texas surpassed previously held flood records by several feet.

More than 100,000 residents were rescued across southeast Texas by both government and civilian resources with more than 40,000 sheltered in over 150 shelters.

Over 336,000 customers lost power during the hurricane mainly across the coastal bend from wind related damages, but also in the Houston and Beaumont areas from flooding.

Harvey resulted in 125 billion dollars in damage making the hurricane the second costliest hurricane in American history (behind Katrina 2005). Harvey is the worst flooding event to ever impact the United States and resulted in the highest death toll from a landfalling tropical system in the state of Texas since 1919 with over 68 direct fatalities (36 in Harris County alone).

2. Drought/Wildfires (2011)

One of the worst droughts to impact the state of Texas and southeast Texas occurred in 2011 resulting in widespread mandatory water restrictions, the loss of millions of trees, and significant wildfires. High temperatures during the drought were some of the warmest on record and exceeded the extreme heat of the summer of 1980.

For the period from February 1 to August 18, Hobby Airport only recorded 6.36 inches of rainfall breaking the previous driest record from those dates by 6.25 inches. On August 27, 2011, Houston IAH reached a high temperature of 109 at 2:44pm which tied the hottest all-time temperature from September 4, 2000 for the city of Houston.

Over the Labor Day weekend of 2011, primed vegetation from the drought combined with strong winds of 30-40mph on the western side of Tropical Storm Lee over Louisiana produced one of the most devastating wildfire events in Texas history. The Bastrop fire burned over 35,000 acres and some 1600 homes and is the single most devastating wildfire in Texas history.

The tri-county fire (Waller, Grimes, Montgomery Counties) burned over 19,000 acres and some 100 homes. In September 2011, the statewide PDSI index fell to -7.97 or its lowest values ever, indicating the 2011 drought was nearly as equal in severity as the drought of record in the 1950’s.

For 2011, Tomball averaged a rainfall deficit of over 40 inches. Overall statewide water storage fell to 58.78% at the end of October 2011 and Lake Conroe fell to -8.0 feet below its conservation pool. Lake Travis fell to -54.61 feet below its conservation pool or (34% capacity). 644 jurisdictions across the state were under mandatory water restrictions.

The City of Houston also recorded 47 days above 100 degrees (previous record was 32 in 1980). Huntsville recorded 72 days above 100 (previous record was 43 in 1980). The incredible heat of August 2011 was estimated to be a 10,000 year return event for the City of Houston.

3. Tropical Storm Imelda (2019)

Tropical Storm Imelda formed 15 miles off the coast of Brazoria County and made landfall near Freeport on September 17, 2019. Imelda would slowly drift north-northeast across SE TX during the 18th and into the 19th.

Early on the morning of the 19th an extensive band of heavy thunderstorms producing extreme amounts of rainfall developed from Jefferson County to east-central Montgomery County.

Rainfall rates under this band frequently exceeded 4.0-5.0 inches per hours with a few locations receiving over 6.0 inches per hour.

This band of excessive rainfall drifted south-southwest in Harris County by mid morning. 31.0 inches of rainfall was recorded in just 12 hours at Fannett, TX near the Chambers/Jefferson County line with a storm total of 44.29 inches of rainfall at that site.

The 44.29 inches recorded at Fannett, TX makes TS Imelda the 4th wettest tropical cyclone in Texas history and the 5th wettest in US history dating back to 1851.

A 48-hour rainfall total of 29.1 inches was recorded in northeast Harris County near Huffman with 30.4 inches recorded in southeast Montgomery County near Plum Grove. 6.5 inches of rain fell in just 1 hour over the Aldine area of Harris County.

The resultant flooding in Jefferson, Liberty, Chambers, and portions of northeast and north central Harris County equaled and in some cases exceeded that of Harvey.

While overall storm total rainfall amounts were less than Harvey, the duration (intensity) at which some of the rainfall occurred in certain areas was much greater for Imelda than for Harvey yielding in certain instances areas that would flood in Imelda and not Harvey. 3,990 homes flooded in Harris County alone. Several thousand flooded in Montgomery, Liberty, Chambers, and Jefferson Counties.   

4. Tax Day Flood (2016)

On April 17-18, 2016 a slow moving to at times stationary cluster of thunderstorms producing excessive rainfall rates developed over portions of Waller, Austin, northern Fort Bend and western Harris County. Over the next 12 hours rainfall amounts of 12-24 inches would occur from southern Waller County into portions of western Harris County resulting in extensive and severe flooding.

The flooding resulted in 9 fatalities in Harris, Waller, and Austin Counties (7 in Harris County) with an estimated 40,000 vehicles flooded and 9,840 homes flooded in Harris County alone.

A maximum 14.5 hour rainfall rate of 23.50 inches was recorded in Pattison in southern Waller County with 19.30 inches occurring at Monaville in 10 hours.

Modern day record flooding occurred along Cypress Creek and in portions of Addicks Reservoir (only to be exceeded a year later by Harvey).

Significant flooding occurred along the lower Brazos River, only to be exceeded a month later when 20 inches of rainfall fell near Brenham, TX. Addicks Reservoir peaked at its highest level ever recorded at 102.65 feet (only to be exceed by Harvey the following year).

5. Memorial Weekend (2015)

Devastating flooding impacted the state of Texas over the Memorial Day weekend in 2015. The initial onslaught began with excessive rainfall and resulting catastrophic flooding along the Blanco River at Wimberley where the river rose over 30 ft in less than 3 hours. It reached a peak elevation of around 40.2 ft (flood stage 13ft) and exceeded the previous record of 33.3 ft (an 86 year old record).

The Blanco River at San Marcos rose 17 ft in 30 minutes and over 29 ft in 2.5 hours.

Over 1000 residents were displaced and over 350 homes in Wimberley destroyed and washed away. The storm killed 13 persons including 8 from a single river house that washed away. The Ranch Road 165 and Fischer Store Rd bridges across the river were completely destroyed and the Ranch Road 12 bridge sustained significant damage.

The following day, a line of intense thunderstorms would originate in central Texas and move into southeast Texas and slow over southwest Harris County. A total of 8.0 inches of rainfall would fall in a 3 hour period.

11.0 inches fell in 12 hours north of US 59 and Beltway 8 resulting in extensive flash flooding. The first ever Flash Flood Emergency was issued for Harris County at 10:52pm. There were 7 fatalities in Harris County (4 from submerged vehicles at underpasses).

Statewide a total of 27 people died in flash flooding. Flooding along Brays and Keegans Bayous was the most extensive since September 1983 and along Buffalo Bayou since March 1992 and TS Allison (2001).

A total of 6,335 homes flooded in Harris County and an additional 3,540 multi-family units flooded. Some of the same homes would be flooded a year later with the “Tax Day Flood” and all would flood again during Harvey 2 years later. 

That’s the decade in review! If you weren’t browning, you were drowning. Any time your friends and family in other states start complaining about the weather there, send a link to this page to them.

Posted by Bob Rehak on 12/31/2019

854 Days since Hurricane Harvey and 103 since Imelda

Photo of the Day #243

Flood debris in Kings Point after Hurricane Harvey.

East Fork Mouth Bar Grows 4000 Feet During Harvey and Imelda

If you boat between the San Jacinto East Fork and Lake Houston, perhaps you’ve noticed it’s a little harder getting from A to B lately. The San Jacinto East Fork Mouth Bar has grown approximately four fifths of a mile during the last two storms and the channel depth has decreased 6X.

These three pictures tell the story dramatically.

I took the first after Hurricane Harvey and the second after Tropical Storm Imelda. The third comes from Google Earth BEFORE Harvey.

East Fork Mouth Bar After Harvey

Looking north toward Kings Point from the East Fork of the San Jacinto River after Harvey. Note fresh sand several feet deep everywhere. Photo taken 9/14/2017, two weeks after Harvey.

East Fork Mouth Bar After Imelda

Extent of East Fork Mouth Bar After Imelda. Photo taken 12/3/2019. Note in this photo how much closer the sandy bottom is to the surface throughout the entire area.

Pre-Harvey to Post-Imelda Growth

Satellite image from January 2017 BEFORE Harvey. Yellow line represents approximate growth in East Fork Mouth bar between then and today – about four fifths of a mile. For alignment purposes, note the tip of the Royal Shores Lake in the first aerial photo and Royal Shores in the second.

Boater Josh Alberson says the maximum channel depth in this area decreased from 18 feet after Harvey to 3 feet after Imelda.

Geologic Change on a Human Time Scale

Note how the leading edge of this growing bar is now almost even with the entrance to Luce Bayou. When we get another storm like Imelda, the East Fork Mouth Bar could block the Interbasin Transfer Project from delivering water to Lake Houston.

Changes like these usually happen on a geologic time scale. They happen so slowly, humans can barely perceive them during the course of a life time. However, Harvey and Imelda produced this change in two years. They provide us with a rare glimpse of a living planet in our own backyard.

If you have children, grandchildren or students, please share these photos with them. They make valuable life lessons about the power of moving water and respect for Mother Nature. They may also stimulate curiosity in Earth sciences and engineering.

Posted by Bob Rehak on 12/23/2019 with depth soundings from Josh Alberson

846 Days since Hurricane Harvey and 95 since Imelda

Liberty Materials Mine Carved Out of Many Wetlands

The Liberty Materials Mine in Conroe on the West Fork of the San Jacinto was cited last month for allegedly discharging 56 million gallons of wastewater loaded with up to 25 times the normal amount of sediment. When we look at the issue of sediment in the river and how it affects flooding, such breaches contribute to the problem. But it’s not just what such sand mines discharge. It’s also about what the wetlands they were carved from don’t hold back any more.

Before there was a Liberty Materials in Conroe, the area they now occupy contained many densely forested wetlands. Now there is nothing to slow down the water during heavy rains. Much more sand and sediment are exposed. And the wetlands are no longer there to filter it. It’s a double whammy. We get it coming and going.

Green areas mapped as wetlands in USGS National Wetlands Inventory. See descriptions below.

Before Liberty, Abundant Wetlands

Visually, it appears that wetlands once covered roughly half the area of this mine. But what was actually there?

US Geological Survey (USGS) and US Fish and Wildlife Service (USFWS) use a five character alpha-numeric code to classify wetlands. Liberty Materials operates in areas that were classified as PFO1A and PEM1A.

P stands for the class: Palustrine. Palustrine wetlands include any inland wetland that lacks flowing water. The word palustrine comes from the Latin word palus or marsh. Wetlands within this category include inland marshes, swamps and floodplains covered by vegetation.

The second two letters in each case stand for the subclass: FOrested or EMergent. Forested means it had broad-leaved, deciduous trees or shrubs taller than 6 meters. Emergent means it had aquatic plants.

These were areas that could store large volumes of water during floods. Plus, they had vegetation that could suck it up.

Trees Soak Up Water, Too

Trees can soak up 50 to 300 gallons of water in a day depending on their size, age and type. They send it back into the atmosphere; let’s use 100 gallons as a conservative average and do some simple math to calculate their contribution to flood reduction.

It’s difficult to estimate the number of trees per acre; it depends on the factors mentioned above plus more. But some people use 500 trees per acre as a good average for estimating purposes.

The Liberty sand mine complex comprises more than a thousand acres. That’s 500,000 trees each soaking up 100 gallons of water per day. Or 50 million gallons of water per day.

That’s about the same amount that the TCEQ estimates the Liberty Mine discharged downstream in one breach.

Personally, I’d rather have the trees and wetlands than white water and a river that’s so silted up it contributes to flooding.

Influence of Wetlands on Flooding

Imagine a sand box that’s 1.5 miles wide and 2.5 miles long. Here’s what it looked like the day after the peak of Hurricane Harvey.

Image from 8/30/2017 of Liberty Mine one day after the peak of Harvey.

And here’s why. Note how closely the extend of flooding matches the extent of the flood plains. Like almost all mines on the West Fork, this one lies substantially within the floodway and floodplain.

Cross-hatched = floodway; aqua = 100 year; tan = 500 year floodplain.

Is Liberty’s Luck Running Low?

If these people had the strongest dikes in the world, maybe you could cut them some slack. But they don’t. They breach repeatedly.

About a month after allegedly discharging 56 million gallons of process wastewater into the West Fork, the only thing holding back another discharge at the Liberty Mine is a couple feet of sand. Photo taken on 12/3/2019.

We need sand, but not at the expense of floods and the environment. Maybe it’s time for TACA to run some of its members out of Texas. That do-good routine they stage in Austin every other year could be in jeopardy with members like Liberty. See below.

11/4/2019. The Day the West Fork Turned White. Confluence of Spring Creek and West Fork. TCEQ alleges that Liberty Mines discharged 56 million gallons of white waste water into the West Fork.

Posted by Bob Rehak on 12.5.2019

828 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.

SJRA To Hold Meeting Thursday at 6 p.m. To Discuss New Flood Forecasting Tool

The San Jacinto River Authority (SJRA) will hold an initial public meeting tomorrow night to discuss its Flood Forecasting and Reservoir Operations Tool project.

  • Date: Thursday, October 24, 2019
  • Time: 6:00 p.m.
  • Place: SJRA General and Administrative Building Board Room, 1577 Dam Site Road, Conroe, Texas, 77304

Objectives of Forecasting Tool

The SJRA hopes to develop a tool that can:

  • Predict peak release rates of storm water from Lake Conroe
  • Anticipate peak water levels in Lake Conroe during rainfall events based on weather forecasts, observed rainfall, lake levels, and other data
  • Improve communication with Offices of Emergency Management and the public during storms. 

Need for Faster, Better Information

“Getting information out as early as possible is essential during potential floods,” said Chuck Gilman, Director of Water Resources and Flood Management for the SJRA.  

“The Flood Forecasting and Reservoir Operations Tool will take data from across the region and analyze it utilizing a model of the Lake Conroe Watershed to make predictions regarding flood threats. That will help us provide timely, accurate information for people to make decisions to protect themselves, their families, and property,” he added.

The gates at Lake Conroe can release water at up too 150,000 CFS. During Harvey they released almost 80,000 CFS.

During Hurricane Harvey, many people lost vehicles and valuables that could easily have been saved by driving them to higher ground if they had had more warning time. This project should help with that.

Available by Fall 2020

The Project will complete in fall 2020. A written technical memorandum will summarize recommendations for the tool. 

The Texas Water Development Board (TWDB) and SJRA will jointly fund the project. TWDB offers grants to political subdivisions in Texas for evaluation of structural and nonstructural solutions to flooding problems and flood protection planning. 

To Offer Input

Anyone interested may attend the meeting to express their views with respect to the project.  

Questions or requests for additional information may be directed to:

  • Matt Barrett, P.E.
  • Division Engineer
  • SJRA
  • 1577 Dam Site Road
  • Conroe, Texas 77304
  • Telephone (936) 588-3111

If you plan to speak, contact Matt Barrett either in writing or by telephone in advance of the meeting. If you cannot attend but have views you would like to share, contact Barrett today.

For additional information on SJRA, visit www.sjra.net.

Posted by Bob Rehak on 10/23/2019

785 Days after Hurricane Harvey

Kingwood Docks Development Submerged

During Imelda, most of the new Kingwood Docks development in Town Center went underwater and stayed that way for days. Much of it is still underwater. Many people have expressed concerns about the development of this area in recent months. It frequently floods. They worry about the potential for the development to increase flood risk for surrounding homes and businesses.

Let’s look at this property, its history, and the plans for it.

Repetitive Flooding

When the site was apartments for the first 30 years of Kingwood, it had a history of flooding repeatedly. It still does. It went underwater during Harvey, May 7th, and Imelda – three times in the last two years.

Here’s what the site looked like before redevelopment into commercial space. Note the triangular area at the far right.
Here’s what it looked like a couple years ago. Lovett started clearing the land on the end.

Entire Property in Flood Plain

FEMA’s National Flood Hazard Layer Viewer shows the entire development is in the 100 year flood plain (aqua). Brown areas represent the 500 year flood plain. Unshaded areas (top right) are not in a known flood hazard zone.

Restaurants with a River View

Since 1998, this site went through a series of five owners. All chose not to develop it once they discovered the site’s problems … until now.

Lovett Commercial bought this property in 2014 under the name Kingwood Retail Partners LTD. They intend to develop this area into a strip of restaurants. During heavy rains, those restaurants will have a river view. Except no one will be able to park by them.

Here’s what the area looked like from Kingwood Drive on 9/19 as rains for Imelda receded. Photo courtesy of Josh Alberson.

How High the Water Got

The debris on this sign shows how high the water got in what will become the parking lot/entry area. Docks! A prophetic name if ever there was one. Perhaps someone was trying to turn a negative into a positive.
What the parking area looked like the day after the storm. Water stayed like this for days. Part of it is still under water a week after Imelda.
Photo taken 9/21/19 shows erosion to pad site. The restaurants themselves will be built up 6-7 feet. Get out your climbing gear. That’s going to be one hell of an ADA ramp.

More Restaurants Planned

Lovett will build twin 14,000 sf structures on that elevated portion (right). They hope to squeeze five restaurants into them. Each structure will measure 200 ft x 70 ft according to their plans.

This shows part of what will become a detention pond around the eastern perimeter of the site. Note how it’s much lower than the creek next to it.
Another view of the “mitigation” area. Photo taken Saturday 9/21/2019. Two days after Imelda, it still had not drained.

The parking will be underwater when it rains. So think seafood restaurants. (Sorry.) Crawfish anyone?

Lessons of History

The current owners bought this property in 2014, about the time that the adjacent apartments were cleared to make way for the HEB center. Lovett began clearing its land in 2016, as HEB and Memorial Hermann Convenient Care Center began construction. By Hurricane Harvey in August 2017, they knew something was terribly wrong.

Lovett knew that its land was lower than the adjacent shopping center as you can clearly see from this Google Earth photo dated 8/30/2017, one of the last days of Harvey. Look where all the water ponds!

Lovett clearly saw the catastrophic flooding during Harvey. Torchy’s, adjacent to them, flooded to the rafters during Harvey. So did every other building in the center.

Despite all that, Lovett started developing the property in earnest this year. Their sign promised that retail space would be available by Fall of 2019. It’s now Fall, and from the photos above, I doubt the owners will have it ready in the next three months.

Ain’t No Arguing with Mother Nature

I spent the last two years writing about flooding. One thing has become perfectly clear to me. We have flooding because people don’t respect the power of water. They think they can win arguments with Mother Nature. So in the name of science, engineering, free enterprise and private property rights, they build in areas where they should not. Confident that they will have the National Flood Insurance Program to bail them out when Mother Nature puts her foot down.

The Simple Solution to Flooding

If we want to stop flooding, we have to stop pushing the envelope into questionable areas. We pay lip service to that idea, but, here we go again. It’s death by a thousand cuts. One parcel at a time.

Posted by Bob Rehak on 9/26/2019

758 Days after Hurricane Harvey

All thoughts in this post represent my opinions on matters of public policy and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP statute of the Great State of Texas.

Study Suggests Large Cities Like Houston Can Intensify Rainfall and Runoff From Hurricanes

A November 2018 article appearing in the peer-reviewed scientific journal Nature found that urban growth can intensify both rainfall and runoff from hurricanes. Further, urban growth can increase the risk of flooding and shift the location of flooding. The article specifically studied the effects of Hurricane Harvey on Houston and found that urban growth increased the probability of such an extreme flood across the basin by 21X.

A sister publication, Scientific American, reviewed the article the same month and helped explain the findings in Nature.

The Nature study looks at two distinct effects of urbanization. The first is the impact of impervious surface on RUNOFF. The second is the impact of the urban landscape’s surface roughness on RAINFALL.

The Runoff Component

Numerous studies have looked at the relationship between percentage of impervious cover, runoff, and flooding – a well documented phenomenon. Impervious cover accelerates transport of rainfall from neighborhoods to rivers. That raises peak flows rather than spreading them out over time. Dr. William Dupre, professor emeritus from the University of Houston visualized the relationship this way.

Effect of Urbanization on Peak Stream Flows” by Dr. William Dupre, professor emeritus from the University of Houston.

Rainfall Component Much Less Studied

However, the effect of urban growth and a city’s surface topography on RAINFALL from hurricanes is much less studied. The authors say in Nature that, “Urbanization led to an amplification of the total rainfall along with a shift in the location of the maximum rainfall.” (Page 386).

“Much less is known regarding the urban effects on the organized tropical rainfall of a hurricane, in particular during one like hurricane Harvey, which stalled for several days.” They continue, “…experiments (with computer models) clearly show a large increase in rainfall arising from urbanization over the eastern part of the Houston area.”

The authors compared present and past urban landscapes and also modeled a scenario in which the entire region was cropland.

Mechanisms Responsible for Increase Rainfall

To understand the physical mechanisms responsible for the heavier rainfall, they analyzed the vertical convergence of winds and wind fields.

Kingwood Greens Evacuation During Harvey by Jay Muscat
Evacuation During Harvey. Photo courtesy of Jay Muscat.

“The enhanced rainfall … and the shift of rainfall … are tied to the storm system’s drag induced by large surface roughness,” say the authors.

Scientific American explains in more detail. Kerry Emanuel, an atmospheric scientist at Massachusetts Institute of Technology, who did not work on the study said, “We know cyclones are sensitive to characteristics of the surface—mountains, streams, marshland. This new twist is that cities have become big enough to tangibly alter the storm.” Said Gabriele Villarini, an environmental engineer at The University of Iowa and an author on the study, “We removed the urban areas from Houston and replaced them with cropland.”

“The presence of urban areas enhanced all the things you need to get heavy precipitation,” Villarini, one of the study’s authors says. “A stronger drag on the storm winds, associated with a larger surface roughness length” contributed to the increased rainfall.

Emanuel explained, “First, the artificial ruggedness of an urban area slows air down. Whenever air slows in a hurricane, he says, it gets shunted toward the center of the storm and up into the sky. That increases rainfall everywhere [in a metropolitan area].” He added, “A storm moves particularly slowly over downtown areas where buildings are tallest, but the winds bearing down from outside the city are still moving quickly. So, [the storm] is piling up on the city.”

Impact on and Implications for Houston

This increase in urban growth in flat terrain creates problems from a flood perspective, despite mitigation measures already in place.

Urbanization has increased the probability of an event like the flooding associated with Hurricane Harvey by about 21 times, say the authors in Nature on page 388.

The authors make several high-level recommendations.

  • Urban planning must take into account the compounded nature of the risk now recognized.
  • Flood mitigation strategies must recognize the effect of urbanization on hurricanes.
  • Weather and climate models must incorporate the effects of urbanization to increase forecast accuracy on local and regional levels.

“It is critical for the next generations of global climate models to be able to resolve the urban areas and their associated processes,” conclude the authors.

About the Authors and Models

The authors are:

  • Wei Zhang and Gabriele Villarini from the Department of Hydroscience & Engineering, The University of Iowa, Iowa City, IA
  • Gabriel A. Vecchi from the Department of Geosciences, Princeton University and the Princeton Environmental Institute, of Princeton, NJ
  • James A. Smith from the Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ.

This presentation explains the Noah Model that the authors used to calculate air/ground interactions.

Local Questions Raised by Study

To date, the role of a city in altering rainfall during tropical cyclones has received very little attention. Houston has had the largest urban growth and the fifth-largest population growth in the United States in the period from 2001–2011. Much of that growth is now on the periphery of the city. The two fastest growing parts of the region are Fort Bend and Montgomery Counties.

As the city grows, we need mitigation measures that can offset the impact of that growth. That’s why the meeting of the Montgomery County Commissions on August 27th is so important. They will vote on whether to close a loophole that allows developers to avoid building onsite detention ponds. Closing that loophole is important. It will help protect hundreds of thousands of downstream residents as well as those in Montgomery County.

Also, the new NOAA Atlas-14 (rainfall measurements updated after Harvey) does not consider forward-looking urban growth effects. The precipitation frequency data in NOAA Atlas 14 was determined by a statistical analysis of historical rainfall, a key input for FEMA Flood Insurance Rate Map (FIRM) modeling. With all that uncertainty, we need to err on the side of caution in flood planning.

For more about Atlas 14, see this link.

Posted by Bob Rehak on 8/18/2019

618 Days after Hurricane Harvey

New Presentation Looks at Role of FM1960 Bridge in Harvey Flooding

Charles Jones, a Lake Houston Area resident and business man, has developed a presentation that examines the role of the FM1960 bridge in Harvey Flooding. The small openings in the bridge, he says, constrict the flow of floodwaters, much like sand gets pinched and backed up when moving through an hourglass.

You can download and review the entire presentation here. It will be stored permanently under the Other Flood Mitigation tab of the Reports page on this web site.

Summary of Jones’ Theory

The following three slides sum up the heart of Jones’ theory.

Most of the flooding during Harvey happened above the FM1960 bridge on the East and West Forks.
The bridge is mostly a causeway. It has two small openings that total 1700 feet.
The two openings restrict the flow compared to other bridges and create a backwater effect.

Discussion of FM1960 Theory

Jones’ presentation is a deliberately “high level”, simplified discussion targeted at a general audience. Parts of it seemed a bit OVERsimplified at times.

For instance, at one point he describes the FM1960 bridge as the cause of sediment build up in the mouth bar area on the West Fork. But if that’s the only cause, why isn’t there a similar build up on the East Fork?

Another example: he describes the West Lake Houston Parkway Bridge as 3700 feet in length. That’s true. But so much sand is stacked up on the downstream side of the bridge that it effectively narrows the opening. See sand in the treetops below.

Looking north toward Kingwood’s Kings Harbor. The West Lake Houston Parkway bridge is on the left. Photo taken two weeks after Harvey. In the foreground, sand now reaches the tree tops and is virtually as high as the bridge itself. Water used to flow under the bridge and through the area in the foreground during floods. Now it is forced north.

However, put those observations aside for the moment and ask two simple questions:

  • Are the principles behind Jones’ theory generally true?
  • Are there any direct observations available that support the theory?

The answers are yes and yes.

“There’s Always a Bottleneck Somewhere in Every System”

I had a client for 35 years that made plastics. The company was one of the largest and most respected in the business. They built plants around the world. A process engineer in that company, whom I highly respected, once told me, “There’s always a bottleneck somewhere in every system.” The FM1960 bridge is ONE of those bottlenecks.

Other Support for Theory

But what about the direct observations?

Note the different shades of brown near the FM1960 Bridge and how the flow within those colors is disrupted by the bridge, especially by the smaller eastern opening. Satellite image from 8/30/17 DURING Harvey.

So pardon the pun, but I think Jones’ theory holds some water. It certainly merits further investigation. I would certainly like to know the answers to the following questions:

  • Did someone actually measure the difference between the high water marks on each side of the bridge during Harvey?
  • If so what was it? Can the backwater effect of the causeway be quantified?
  • Is there photographic evidence of any difference?
  • If the backwater effect is significant, how much would it cost to modify the bridge? Would the benefits justify the cost?

Thank you, Mr. Jones, for bringing this matter to the public’s attention. You’ve made a valuable contribution to our understanding of Harvey.

And On a Side Note…

What’s that nasty brown stuff flowing out of Luce Bayou on the upper right in the photo above? At first I thought I might be the shadow of a cloud on that particular day, but it shows up consistently in other photos. See below, for instance. It starts about the time construction on the Luce Bayou project started. That’s the project designed to bring water to Lake Houston from the Trinity River. Mmmmmm!

Satellite image from 12/30/2014 shows purple/brown effluent coming from Luce Bayou. Note the three distinct sediment colors in this photo: light brown in the West Fork on the left, medium brown from the East Fork at the top, and dark brown from Luce Bayou on the right.
Most recent Google Earth image from 2/23/19 shows that water coming from Luce Bayou is more normal in coloration now. Construction on the Interbasin Water Transfer Project is required to be complete this month. Let’s hope that’s the last we see of that purple stuff.

Posted by Bob Rehak on 6/14/2019

654 Days After Hurricane Harvey

John Rocco’s Harvey Experience: Death and Destruction in the X-Zone

John Rocco lives in Kingwood Greens where 225 out of 225 homes flooded according to statistics compiled by the Kingwood Service Association. John is a man of few words. He let these images tell the story for him and sketched out a few details (see below). All images were taken after he was able to re-enter his home. I can only imagine his horror. It looks like his whole home was shaken, not stirred. But the home wasn’t the real tragedy.

John Rocco #1
An inch of mud and flood damage up to the door knob.
John Rocco #2
Fine layers of silt cover everything.
John Rocco #3
Large screen TV flipped off its stand
John Rocco #4
Fridge on the fritz
John Rocco #6
Kitchen needs aide!
John Rocco #7
What 240,000 CFS can do to your home
John Rocco #8
His life was turned upside down.
John Rocco #10
Buried treasures.
John Rocco #11
Room no longer fit for living
John Rocco #12
Uncalm after the storm
John Rocco #13
Come right in and sit awhile!

Death and Destruction in the X-Zone

Said Rocco,  “I’m supposedly not in a flood plain (Zone X) and I did the research on the build up of the Greens area after the 1994 flood before buying here in 2015. My house was built in 2005. Before moving here, I lived on Scenic Shore in Kings Point since 2001.”

“My son lost his house in the Enclave as well as his business next to the FEDEX store. We restored both as well as my house. My neighbor and I rescued the 90-year-old next door just as the water was within an inch of covering her bed in her first floor master. She had no idea. Unfortunately, she died about 2 months later.” 

“My wife was suffering with stage 4 cancer. I had to carry her out of the house in waist deep water to a rescue boat that our son arranged to pick us up. She was in shock. She caught pneumonia twice,  spent time in the hospital. She passed away in May, 2018, nine months later. I’m not blaming the flood per se, but it certainly had an effect.”

“I will say this. I will not restore all this again if we don’t get appropriate actions to mitigate flooding problems.”

Directly Impacted by Mouth Bar

Thank you, John, for reminding our political leaders of the pain that thousands of residents suffered. The homes in Kingwood Greens, like those in Foster’s Mill, Kings Point, Kings River and Atascocita Point were directly impacted by the mouth bar.

A year and a half after Harvey, a year after Mayor Turner said the mouth bar would be removed, and six months after “everybody but Trump” met in Austin and agreed in principle to remove it, not one cubic yard has been removed.

Performance, Not Promises

As we head into another election season AND another hurricane season, we need to remind our elected officials that it’s time for performance, not promises.

Posted by Bob Rehak on March 14, 2019

562 Days after Hurricane Harvey