The Blanco River runs through central Texas and was one of the worst parts of the disastrous floods that hit the state this week, with 3 people confirmed dead and 9 others currently missing after that river broke through its banks.
A disaster like this has many different stories to tell. The rainfall amounts in Texas recently are enormous and solid cases can be made linking them to both a developing El Nino event and climate change (directly linked through unusually warm waters in the Gulf of Mexico and the Pacific Ocean). However, in this post I’m going to focus on an issue we have more direct control over: development.
Human development makes floods worse. That’s a strong statement and it is very well scientifically supported – in fact you can go outside and do the experiment yourself. Take 2 pitchers of water, pour one on some open grass, and pour another on a paved surface. The water poured on the grass may flow for a little bit, but eventually it’s going to enter the soil. On the other hand, none of the water poured on a paved surface will enter the soil at first. It will flow downhill until it reaches a trap: a storm drain or a low spot nearby.
Now look around and ask, “how much of the surface area around me is paved?” That includes building roofs, streets, sidewalks, parking lots, etc. In undeveloped areas, the ground surface is generally “permeable” meaning rainwater can infiltrate into the soil and move downwards. Paved surfaces on the other hand are mostly impermeable; water must flow over them and cannot penetrate downwards.
Even a moderately developed area can see the amount of impermeable surface increased to 25% just by roads and buildings, but in urban city cores the amount of impermeable surface can top 90%. When a surface is made impermeable, rainwater is either concentrated in area that is permeable or it is pushed into manmade storm drains; the capacity of both can easily be overwhelmed in a large rain event. A paved city with 10% permeability has to find a place to put 90% of the rain that falls on it; otherwise the end result will look like this photo.
Paving surfaces isn’t the only part of development that impacts flooding; wetlands have a large capacity to absorb floodwaters and prevent damage downstream, but people can develop wetlands as farming and riverfront property. Soils generally have good infiltration rates, but farming practices can also reduce those, further increasing storm runoff. Finally, developing in floodplains puts people’s lives and property directly at risk since they’re living in those areas.
The Blanco River is outside of Austin, Texas, one of the fastest growing urban areas in the United States. The population of the county where the most severe flooding occurred has literally doubled within less than a decade – it is rapidly urbanizing. This not only puts more people at risk from the same flood, it will make floods worse. This rainstorm would have still caused major flooding throughout Texas, but every few centimeters of water height at the peak of the flood winds up causing more damage and putting more people in jeopardy.
The end result of this problem can’t be “don’t build cities” because people do want to live places. Instead, there are a variety of other solutions to these issues. Many cities are developing flood control infrastructure – large reservoirs or open spaces where storm drain overflow can be pushed during a storm. Chicago, for example, has developed a system to use a gigantic open-pit limestone mine on the city’s south side as a location where storm overflow can be pushed during a storm to limit major flooding.
Other types of green infrastructure can help too. Small things, such as rain barrels that collect water off of roofs, can make a difference if they’re deployed over a large area. Green infrastructure can help too – designing parks or landscapes such that water can enter the ground and migrate slowly downhill within them rather than pouring rapidly over the surface and into flooding rivers can reduce the peak flood magnitudes.
However, that topic brings us back to Texas, because those projects cost money. Texas in general puts very few restrictions on development and thus does not have organized plans to deal with these risks. Major cities may have some flood control measures, but the state does not fund flood control infrastructure development and there is no plan for managing floodplains or limiting development in at-risk areas. A single city can only do so much if the floodplain upstream is developed.
The state has several thousand dams that can help limit flooding, but many of them are privately owned and not regularly inspected. On those that are managed by the state, quality control is low due to high costs and an average of 4 fail per year. As a consequence, when these types of storms hit Texas, the damage they do is maximized – people are permitted to develop on floodplains and that development both makes the flood worse and puts more people at risk.
The U.S. Government manages the National Flood Insurance program as private insurers pulled out decades ago when they were unable to assess flood risks. Outside of large events such as Hurricane Katrina, Texas is the leader in receiving flood damage payments per year. Furthermore, when a huge disaster like this storm strikes, Texas will receive disaster response and rebuilding assistance from the federal government as well.
Because of these policies, the people who live in the flood plains are put at risk and the U.S. taxpayer is put at risk, but that alone will not be enough to lead to more sensible development or integrated flood-control policies.
Image credit: Drew Anthony Smith/Getty Images http://huff.to/1AybaBw
Read more/References: http://t.co/8OtIYbIec5 https://www.hcfcd.org/ http://bit.ly/1AyGeB4 http://bit.ly/1Q8QgdW http://nyti.ms/1AyGjVo http://on.mash.to/1HwSlfk http://nyti.ms/1cjOU2C
