The Ike Dike:
A Dutch Perspective

In case you missed it over the weekend, the Chronicle published some of my reflections the levee system in the Netherlands that I had the opportunity to visit recently. http://www.chron.com/disp/story.mpl/editorial/outlook/6525027.html

There are many interesting aspects to the Dutch system, but undoubtedly the most impressive is the massive sea gate at Maeslantkering. This structure was built to provide a means to stop tidal surge from flooding the area around Rotterdam by backing up the Nieuwe Waterweg (part of the Rhine estuary system). The problem that the Dutch faced was that the Nieuwe Waterweg is one of the busiest waterways in the world, with a ship passing though it on the average of every 8 minutes. As a result, a traditional lock system was unworkable.

The reason the Maeslantkering sea gate is of particular interest to our area, is that it suggests a possible solution to building a levee system to protect the Texas Gulf Coast from a hurricane surge. To accomplish this, it would be necessary to have the means to block off the Houston Ship Channel, a daunting task to say the least.

The most logical place to attempt such a feat would be between the tip of the Bolivar Peninsula and the east end of Galveston Island. At that point there is about 1.5-mile expanse of water that begins very shallow on both sides but drops off fairly quickly to a depth of 15-20 feet then gradually deepens to the Ship Channel's depth of 40 feet.

The Ship Channel is about 500 feet wide in this area, however, the water immediately outside the channel is over 30 feet deep providing some maneuvering latitude. Preliminary concepts, such as Bill Merrill's design, contemplate a levee stretching from each side to a Maeslantkering-like sea gate across the Ship Channel. It is clear that a structure of that size can feasibly be constructed. The Maeslantkering gate actually spans about 1200 feet, more than twice the width of the Ship Channel.



Recently, the Dutch officials that operate the gate were kind enough to give me a tour of the facility. It is an imposing structure. In many ways it reminded me of an offshore drilling rig lying on its side.



The design is ingenious, but the technology is surprising simple. The arched barriers are actually large submarines. In their "resting" position, they float. When the gate is closed, small diesel engines on each side float the gates into the river using a simple cog and cam track. Once they are in place, they are flooded and sink to the river bottom.

The river bottom has been reinforced with a footing that is topped with enormous concrete blocks so that the gate has a hard surface on which it can sit. Interestingly, the bottom actually silts in over time and the gates initially "land" on this silt, about three feet above the concrete footings. However, the rush of water under the gate clears out the silt in about an hour when the gates make their final landing on the concrete sill.

The arched barriers are supported by trusses that are attached to a gigantic ball joint. The ball joint allows the trusses to articulate horizontally and vertically. Each arm can withstand a force of 70,000 tons.


The gates can be opened and closed in a matter of hours. In its ten-year history it has only been closed once on account of a storm. However, there is a test closing annually just prior to the start of the Dutch storm season. (BTW, the test closing this year is September 19-21. It apparently attracts thousands of observers. If my schedule permits, I intend to be one.)


The Dutch began contemplating a surge barrier in this area in 1979. Less than 20 years later, the Maeslantkering sea gate was completed in 1997. The total cost in 1997, was about €450 million (approximately $630 million). The annual maintenance is about €5 million ($7 million).

The gates are about 70 feet tall. With a channel depth of about 50 feet, the gates create about a 20-foot wall above normal tide levels.


One interesting aspect of the gate is that it does not completely shut off all of the water. There is about a five-foot gap between the gates to prevent them from colliding into each other. Also, some water flows around the end of the gates in the channels cut for their resting position. According to the Dutch officials, the gates block about 98% of the water, assuming that the surge does not over top the gates. However, to reduce the flood level on the back side of the gate it is not necessary to block all of the water.

There are, of course many questions as to whether such a sea gate is feasible for the Houston Ship Channel. Before undertaking what would likely be a billion dollar plus project, we would certainly want to conduct an extensive study, including an examination of the potential environmental impacts. Nonetheless, I found the Dutch will to overcome the sea and protect their communities from its ravages inspiring. I think theirs is an example we should follow. I do not believe that doing nothing is an option. I guess I must have some Dutch blood.

For more information see:
http://www.keringhuis.nl/engels/home_flash.html

Click here to see the Keringuis Website

Click here to view the Video "Storm Surge Barrier on the Nieuwe Waterweg"

The Ike Dike

Last week the Governor's Commission studying the Hurricane Ike recovery unanimously recommended to the Governor and the Legislature that a study be funded to determine the feasibility of a comprehensive levee system to protect the Texas Gulf Coast from future storm surges. The recommendation was prompted by presentations made to the Commission by Texas A&M of a concept levee system that would block storm surges from entering Galveston Bay. The proposed system has been dubbed the "Ike Dike."

To be perfectly honest, when I first heard the idea, I thought it was a bit outlandish. But as the Commission has studied the issue, all of us became convinced that the concept warrants a serious and detailed consideration.

The Ike Dike is the brainchild of Texas A&M Galveston's Bill Merrill. To review his PowerPoint presentation click here. The dike envisioned by Merrill would extend from High Island to somewhere south of the San Luis Pass and is specifically designed to protect the Galveston Bay environs. However, the Commission's recommendation is that a study that would include the entire Texas Gulf Coast.

The project would basically create a 17-foot wall along its entire length, incorporating the existing Galveston seawall. There are several possible designs, but the one that probably is most viable would be building a levee along the existing FM3005 and SH87 right of ways. These are already at about a 5-foot elevation, so they would only have to be raised by twelve feet to get the design elevation.

Of course, the challenging part is how to keep the surge from barreling up Houston Ship Channel through the Bolivar Roads. This will require creating a gate that will close off a nearly two-mile stretch of open water. As bizarre as this may sound, there is actually such a barrier across the Rotterdam channel in the Netherlands that spans a wider gap. Clearly, we do not have enough information at this time to make an informed judgment on the feasibility or advisability of such a project.

Bolivar Roads

However, the Commission did ask some basic questions. This is what we found.

Cost. The obvious questions are "how much" and "how would we pay for it." Merrill estimates that the Galveston Bay portion of such a levee would cost about $3 billion in today's dollars. This frankly would be a fairly modest investment comparatively speaking. The estimated damage from Ike alone is in excess of $30 billion. Not all of the damage would have been prevented by such a levee system, but clearly it would pay for itself with just one such storm. It is also comparable to other major public works projects in this area. The expansion of the Katy Freeway and Metro's LRT project both have similar price tags.

The federal government would likely be willing to substantially subsidize such a project since it would dramatically reduce claims on the Federal Flood Insurance Program. But even if Texas had to pay for the project alone, it would only take about 5-6¢ property tax on the affected counties to finance the project over 30 years. I think it is clear that if Merrill's cost estimates are anywhere close to accurate, the financial hurdle may the lowest one.

One of the more disturbing pieces of information the Commission heard was that industrial and commercial concerns are now reluctant to invest along the Gulf Coast because of its vulnerability to storm surge. It may be that if we do not undertake some protective measures, we will see economic growth stunted in our region by an amount far greater than the cost of such a project.

Will it Work? A number of Commission members were skeptical about whether such a levee could really hold back a Category 5 storm surge. Merrill points out that the Dutch have been holding back the North Sea for centuries, a seemingly more daunting task.

Some of the Commission's questions centered on whether a 17-foot levee was high enough. At places the Katrina storm surge was measured as high as 28 feet. However, the 20+-foot measurements are all inland and not at the coast. A storm surge is exaggerated as it pushes its way into the confines of bays and rivers. According to Merrill, a 17-foot system will stop 95% of the storm surges ever measured. Also, even if a storm surge topped the levee, the effects on the inland areas would still be dramatically minimized.

Environmental Impact. The environmental impact of such a levee system will be the most vexing question. There are obvious and significant environmental benefits. One only need visit Galveston Bay today to see the adverse impact of Ike. Also, friends in the petrochemical industry have told me that if we ever get an Ike-like surge directly up the Houston Ship Channel the ecological consequences will be disastrous; which is easy to believe.

On the other hand, there could be adverse long-term, and perhaps, unintended consequences from constructing such a system. Some environmentalists argue that hurricanes actually have a long term beneficial effect on the estuary system.

One of the concerns raised immediately by environmentalists is the effect on the exchange of water flows between Galveston Bay and the Gulf. In order to build the sea gate that would close off the Bolivar Roads, the opening would have to be narrowed from the current width of nearly two miles to about 1000 feet. Environmentalists worry that this stricture would impede the flow of Gulf water into the Bay along with various species that migrate between the Gulf and the Bay. It might also alter the salinity of the Bay and thereby negatively impact some species.

Merrill is convinced this concern can be addressed by designing the dike to accommodate a sufficient Gulf water inflow. But even if that is the case, there will be many other environmental concerns such a massive project will raise. Part of the vetting process must address each of these with scientific integrity.

Conclusion. Thanks to Ike, I experienced first-hand the effects of a storm surge on my hometown of Kemah. I also remember returning to a nearly totally destroyed Kemah as a child after Hurricane Carla. Therefore, I am probably not entirely objective on this subject. Nonetheless, I have seen the human and financial toll a storm surge has on families and communities. It is truly devastating. If we can responsibly protect future generations of Texans from hurricane storm surges, it would be a great legacy to leave our children and grandchildren.

There are two things I have learned about public policy issues. First, they are always more complex than a causal examination suggests. Second, policies adopted with the best of intentions frequently have unintended, negative consequences. Both of these principles are evident in the amendments that the City made to its flood ordinances in October, 2006. These amendments have spawned a flurry of protests and objections. The opponents of the amendments have even organized their own website. See http://www.houstonfloodway.org/index.htm.

There are many issues involved in this dispute, but at the heart of the controversy is a provision in the amended ordinance that bans all construction in the floodways and limits improvements to existing structures to 50% of their value. The 50% limitation is cumulative over a 10-year period.¹ At first blush, stopping a lot of new construction in areas likely to flood seems like a pretty common sense notion.

In addition to the general idea that people should not be building in an area likely to flood, the City had another reason for amending the flood ordinances. FEMA administers the National Flood Insurance Program. One of its duties is to rank cities based on their efforts to minimize flooding. Residents in cities that score higher on FEMA's ranking system (referred to as the Community Rating System or CSR) pay lower flood premiums. When I was on council and mayor of Kemah, we were able to substantially lower our residents' premiums through aggressively adopting various flood control measures. Likewise, the City of Houston's ratings have significantly improved in recent years, saving Houstonians thousands of dollars in flood insurance premiums. So it is clear that the City should be constantly working to improve our flood control measures.

Many of those who have been very significantly and adversely affected by these amendments have ascribed various sinister motivations to the 2006 amendments. Candidly, I have found no evidence that suggests any motivations other than attempting to improve the City's flood control measures and lower Houstonians' flood insurance premiums. But as Samuel Johnson once said, "The road to hell is paved with good intentions." And this is where some of our neighborhoods feel that they have been sent by these amendments.

It will probably surprise those not familiar with this subject that the definition of what constitutes the floodway is open to some considerable interpretation. I think most of us would assume that the floodway would generally be the area within the banks of the bayous. However, it turns out to be considerably more complex and can cover a much larger area.

The CRS system actually establishes two concepts regarding areas subject to flooding - the floodway and the flood plain. The flood plain refers to areas in which there is a 1% chance of flooding in any year. This is frequently referred to as the 100-year flood plain. The floodway defined at any bayou or channel section as the minimum width of floodwater conveyance to keep flood waters from rising above one foot above the 100-year flood plain elevation. I know, about as clear as mud.² But the general idea is that we want to keep the floodway open to keep people upstream from flooding.

Therefore, the floodway is not an area that is readily demarcated by a physical feature like the bayou banks. It must be calculated by hydraulic engineers based on floodwater flow rates and channel characteristics within the watershed. New maps are periodically issued maps showing the floodways and the 100-year flood plains.

But here is where the rub comes in. Those maps change from time-to-time based on new rainfall data, changes in the hydraulic characteristics of the watershed, or changes in the calculation methodology. The amendments to the City's flood ordinances coincided with such a re-drawing of flood maps based on new elevations that were developed as a result of the Tropical Storm Allison Recovery Project (TSARP) using new Light Detection and Ranging (LIDAR aerial mapping technology and some changes in the calculation methodology.³ The results substantially changed the areas included in floodplains and floodways across the City and County. In some neighborhoods, such as along White Oak Bayou, the areas added to the floodways included many homes and vacant residential lots not previously recognized as being within floodways. With the combination of the new floodway maps and the City ban on new construction on floodway construction, many property owners suddenly found their properties, many of which had never flooded, substantially devalued and some virtually worthless.

Interestingly, the FEMA regulations do not require that the City prohibit new construction in the floodway as it has done in the amended ordinance. In fact, there is no such ban imposed by the County in unincorporated areas. Rather, FEMA requires that the City must regulate construction in the floodway to prevent any new construction from causing additional flooding in the upstream floodplain. Also, it is not clear whether the City gets any credit under the CSR system for the total ban.⁴

Under these circumstances, I believe that the City should revisit the October, 2006 amendments. At a minimum, the outright ban of construction in the floodway should be lifted in favor of a system that would regulate the degree to which any new construction could impede the flow of flood waters. By building with pier and beam construction, it is my understanding the impedance can be minimized or mitigated. Also, the 10-year cumulative damage provision is not required by FEMA and should be revised as well.

When you live in flat coastal plans flooding is inevitable. As result flooding has long been a long-standing and chronic problem in Houston, bringing misery to hundreds of thousands of our neighbors. Therefore, the City should be commended for aggressively moving to reduce this menace. However, as with any initiative, the rights of the minority must be weighed against the general public welfare. In this case, I feel that we have abridged the rights of these property owners to a far greater extent than is justified to protect the greater good.

Bill King
121 North Post Oak Lane, #401
Houston, Texas 77024
weking@weking.net
www.BillKingHouston.com

PS: If you would like to know where your property is with respect to the floodways and flood plains, you can find out at http://maps2.tsarp.org/tsarp/.

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¹ The City has, by administrative rule, made significant exceptions to the 50% limitation.

² The actual definition per FEMA regulations is "Floodway means that portion of the floodplain which is effective in carrying flow, within which this carrying capacity must be preserved and where the flood hazard is generally highest, i.e., where water depths and velocities are the greatest. It is that area which provides for the discharge of the base flood so the cumulative increase in water surface elevation is no more than one foot."

³ LIDAR is technology similar to radar. With this technology an airplane flying over any point can determine to a high degree of accuracy that point's elevation.

⁴ The CSR rules have a point system that awards points for specific flood control measures. There are no points for a total ban of construction in the floodway under this point system. However, FEMA generally opposes wholesale construction in the floodways and has some subjective discretion over the ultimate ranking assigned to the City.