Rebuilding beachfront McMansions








The correct interpretation of the concept of a 500 or 1,000 year flood

A flood expert addresses five myths about floods and this includes the idea that a 500 year flood only happens once every 500 years:

Myth No. 3
A “100-year flood” is a historic, once-in-a-century disaster.

Describing floods in terms of “100-year,” “500-year” and “1,000-year” often makes people think the disaster was the most severe to occur in that time frame — as encapsulated by President Trump’s tweet calling Harvey a “once in 500 year flood!” He’s not alone. When researchers from the University of California at Berkeley surveyed residents in Stockton, Calif., about their perceived flood risk, they found that although 34 percent claimed familiarity with the term “100-year flood,” only 2.6 percent defined it correctly. The most common responses were some variation of “A major flood comes every 100 years — it’s a worst-case scenario’’ and ‘‘According to history, every 100 years or so, major flooding has occurred in the area and through documented history, they can predict or hypothesize on what to expect and plan accordingly and hopefully correct.”

In fact, the metric communicates the flood risk of a given area : A home in a 100-year flood plain has a 1 percent chance of flooding in a given year. In 2018, Ellicott City, Md., experienced its second 1,000-year flood in two years, and with Harvey, Houston faced its third 500-year flood in three years.

That risk constantly changes, because of factors such as the natural movement of rivers, the development of new parcels of land, and climate change’s influence on rainfall, snowmelt, storm surges and sea level. “Because of all the uncertainty, a flood that has a 1 percent annual risk of happening has a high water mark that is best described as a range, not a single maximum point,” according to FiveThirtyEight.

I am not surprised that the majority of respondents in the cited survey got this wrong because I have never heard it explained this way. Either way, the general idea still seems to hold: the major flooding/storm/disaster is relatively rare and the probability is low in a given year that the major problem will occur.

Of course, that does not mean that there is no risk or that residents couldn’t experience multiple occurrences within a short time period (though this is predicted to be rare). Low risk events seem to flummox people when they do actually happen. Furthermore, as noted above, conditions can change and the same storms can create more damage depending on development changes.

So if this commonly used way of discussing risk and occurrences of natural disasters is not effective, what would better communicate the idea to local residents and leaders? Would it be better to provide the percent risk of flooding each year?

McMansions lead to water runoff damage in Kirkwood, Missouri









Henry Grabar poses an interesting question: what if the Deep Tunnel project, one of the largest civil engineering feats in the world, does not solve flooding and stormwater issues in the Chicago region?

What if Chicago took a wrong turn in 1972 when, in the spirit of civic grandee Daniel Burnham (“Make no little plans”), it opted to build the world’s largest sewers instead of making all possible efforts to keep rainwater out of them? Scott Bernstein, the founder of the Center for Neighborhood Technology, says that the Deep Tunnel imposed a massive opportunity cost because the city and the district did little else to adapt. The MWRD spent billions on what engineers call “gray infrastructure” (pipes, tanks, pumps) and virtually nothing on “green infrastructure”: rain barrels, detention ponds, green roofs, porous pavements, and other adaptations that would have kept water out of the system…

The project proceeded regardless. Even with downsized reservoirs and a longer time frame, Chicago’s ambition captured the attention of civil engineers around the world. Today, most U.S. cities whose combined sewer overflows are governed by consent decrees with the EPA are working on Chicago-style digs. St. Louis, which has the fourth-largest sewer system in the country, is under a consent decree to commit $4.7 billion to ending its overflows through deep tunnels…

While engineers’ penchant for megaprojects endures, some American cities are preaching deterrence. If Chicago built a bathtub, Philadelphia is trying to transform itself into a sponge with park space, street trees, and permeable pavement. The city is spending $2.4 billion to implement the nation’s largest green infrastructure plan, an experiment that positions it as the anti-Chicago. The city thinks keeping water out of the system will save billions of dollars compared to a rejected tunnel proposal—and that green initiatives will produce positive externalities, like improving air quality and creating verdant streets.

In Chicago, meanwhile, the MWRD has committed to creating just 10 million gallons of green infrastructure capacity under its EPA consent decree. Compare that to neighboring Milwaukee, a deep-tunnel city that now believes its green infrastructure will, by 2035, surpass the capacity of the tunnels and hold up to 740 million gallons of rain where it falls.

Hindsight may always be a little tricky in these cases as we have the advantage now of being able to see the Deep Tunnel project in action. Does it actually accomplish its goals? Was all the spent money worth it? At the same time, a project of this magnitude should have generated plenty of discussion and at least a few alternative options.

If Deep Tunnel does not work as intended or does not solve all of the flooding and stormwater problems, I wonder if it could be used in other ways. I’m thinking of other major infrastructure projects that have been reversed or reused, like urban highways that are torn out (like in Boston or San Francisco) or former railroad lines turned parks or recreation areas (think the High Line). Some other options for the Deep Tunnel:

  1. Underground roads. With Elon Musk’s Boring Company working on underground roads plus Chicago’s legacy of Lower Wacker Drive, perhaps traffic could be rerouted deep underground.
  2. Underground freight movement. Given Chicago’s railroad bottleneck, this could be an interesting solution.
  3. An underground park and recreation area. It would certainly be unique. Think a combination of spelunking, rock climbing, and exploration.
  4. A military installation and testing area.

Teaching kids about Chicago’s Deep Tunnel project






Invasion of McMansions in Kirkwood, Missouri

Teardown McMansions have infiltrated an older neighborhood in a well-off St. Louis suburb:

Residents said not only are smaller historic homes getting wiped out in the process, but the large houses are causing problems for some of their next-door neighbors…

The one next door to her on Cleveland Avenue was erected last year and is nearly twice the size of the original home. It’s a four-bedroom home on the market for more than $800,000.

She said it’s created a real problem for her. The new home’s rain runoff has turned her driveway into a lake…

The city says the builders have followed all the community’s guidelines:

“…The new house on this site sits closer to the neighbor’s driveway, which may explain the confusion. Yes, the new home was built per permit specifications. The City requires the contractor to have the top of the foundation surveyed prior to beginning framing. The floor system is then verified to determine that the finished floor height is as allowed.

A follow-up story from several days later says the new McMansions are affecting more houses:

Since the homes were built around 2015, Reed said her mother’s basement has constantly been flooded and her backyard has turned into a swamp…

The ITeam recently discovered a Kirkwood ordinance that said new developments cannot cause water run-off problems for surrounding properties.

But attorney Paul G. Henry said getting the city to enforce it could be difficult…

We repeatedly asked Kirkwood officials about why they don’t appear to be enforcing their own ordinance but they declined to answer. Instead, they recommended that we file an information request.

Such issues could put a suburb in a sticky situation: should it protect the properties of elderly citizens who have lived in the community for a long time or allow new property owners to construct homes to their liking? Whose property rights prevail? There is probably some middle ground here where the teardowns can be regulated in such a way to provide a little protection to neighbors (whether this involves water issues or residents are concerned about the changing character of their neighborhoods) but these regulations could take some time to discuss and enact.

Replace Houston McMansions and sprawl with what?

At least a few of the homes flooded in Houston are McMansions. For example, see this video of rescue efforts in one neighborhood where water is past the first floor of McMansions.

Once the waters recede, what will happen to these McMansions? Critics of such homes argue that they are often poorly built. Are they worth restoring and rebuilding or will homeowners pursue other options? What will communities approve and will they promote other options beyond big single-family homes?

Rarely do suburbs and big cities have opportunities to rethink past development decisions on a large scale. Houston is known for sprawl and a number of commentators (including me) have already suggested that such an approach often does not work well with flooding and water issues. Yet, overturning decades of sprawling suburban development is a difficult task and is likely even harder when residents just want to get back into their homes.


“People care about flooding…they don’t care about stormwater management”

An article discussing the difficulties of avoiding flooding in a sprawling city like Houston includes this summary of a key problem:

One problem is that people care about flooding, because it’s dramatic and catastrophic. They don’t care about stormwater management, which is where the real issue lies. Even if it takes weeks or months, after Harvey subsides, public interest will decay too. Debo notes that traffic policy is an easier urban planning problem for ordinary folk, because it happens every day.

It is difficult to get people interested in infrastructure that does not effect them daily or they do not see it. Yet, flooding is a regular issue in many cities and suburban areas and it can be very hard to remedy once development has already occurred. Indeed, it is difficult imagine abandoning full cities or major developments:

The hardest part of managing urban flooding is reconciling it with Americans’ insistence that they can and should be able to live, work, and play anywhere. Waterborne transit was a key driver of urban development, and it’s inevitable that cities have grown where flooding is prevalent. But there are some regions that just shouldn’t become cities.

Given the regularity of flooding in developed areas, it is interesting to consider that there are not more solutions available in the short-term. Portable and massive levees? Water gates that can be quickly installed? Superfast pumps that can remove water?

Flooding as a major suburban problem

Suburbs are often derided for their sprawling development that chew up acres of land and significantly alters more rural settings. Within that sprawl, one problem that consistently shows up but receives less attention than it should is flooding. For example, the significant rain received in parts of the Chicago region this past Wednesday (July 12) has impacted a number of suburbs:

While some suburban communities Saturday saw water levels begin to recede in the wake of Wednesday’s downpour, others still are bracing for the worst of the fallout from flood-ravaged rivers experts expect will crest later today into next week.

In Algonquin, the Fox River reached 11.79 feet by noon Saturday, with the National Weather Service predicting it will crest nearly a foot higher, at 12.9 feet, sometime Tuesday.

As of noon Saturday, The National Weather Service reported the Des Plaines River near Gurnee had reached a record-setting 11.96 feet and was expected to crest at about 12 feet sometime in the next 24 hours. In Lincolnshire, the level had dropped to 15.5 feet, but official predictions indicate the river may rise again to crest at 16.3 feet sometime Sunday.

While Wednesday’s rain was unusual (and we could argue about how frequently such big storms do and should occur), the results highlight a common issue across suburban landscapes: what happens to all that water? Suburbs don’t just change rural or farm land into developments; they change how water flows and is absorbed into the soil.

A variety of techniques are available to deal with the water. Common in this area are retention ponds, sunken areas within developments that are often dry but serve as places where water can pool when excessive rainfall occurs. In the Chicago area, the need to deal with flooding led to one of the largest civil engineering projects in the world: Deep Tunnel. Floodplains are fairly visible during heavy rains as homes and other structures near large bodies of water, particularly rivers, are affected. Less easy to see are  formerly swampy or marshy land which have been filled in, the channeling of creeks and rivers (or even covering them up completely), and covering the ground with less permeable surfaces such as roads and driveways (this can be combated by using different kinds of surfaces).

Instead of viewing flooding within major metropolitan regions as the unfortunate result of large storms, we should see it as a regular issue within suburban settings. And if we do so, that might prompt better plans to avoid the flooding that comes when so much land is altered.

Why Canadian communities may not have an incentive to avoid flood plains

If the costs for rebuilding in flood plains is covered by the provincial and national governments, why would communities limit building on those flood plains?

As the battle to protect homes from flooding continues across the country, questions are being asked about whether it’s time to reconsider regulations that allow developers to build on flood plains.

Jason Thistlethwaite, an assistant professor at the University of Waterloo’s faculty of environment, says the problem is that municipalities set zoning regulations and collect property tax revenue but do not pay for rebuilding costs after natural disasters.

“The municipality really doesn’t have an incentive to go in and use land-use planning and building codes and communications strategies to tell people that they are at risk of flooding, particularly given that most of the revenue comes from development, it comes from property taxes.” Thistlethwaite said. “So they face a real conflict of interest…

Last February, the Parliamentary Budget Office released a report estimating that over the next five years the federal government will dole out an estimated $902 million a year in disaster-related relief to provinces and territories.

I could see at least two good arguments against building in flood plains:

  1. The financial costs in the long run. Of course, the suggestion here is that local communities don’t bear the costs. But, even if they are paid at higher levels, the costs are going to get passed down eventually. Additionally, communities might benefit from property taxes but the reconstruction times and costs also would limit the property taxes they can collect.
  2. Environmental reasons: it can’t be good to have buildings and other debris from the built environment consistently washed into waterways. Limiting development on floodplains also allows for rivers and other waterways to go through natural cycles.

Either could be a good enough reason. However, as noted above, it is very difficult for communities to pass up on allowing development on desirable properties. There are similar situations in the United States.

One of the better options I’ve seen in some suburbs is to convert these flood areas to parks. This accomplishes two purposes: (1) when flooding does occur, the damage is reduced since it affects fewer buildings and (2) having a park nearby can enhance property values and the quality of life.