03 May 2006

Flood Planning In Denver and New Orleans

Talk of rebuilding New Orleans over at the Unbossed blog has brought my thoughts back home to Denver.

Good urban planning uses strategic placement of green space and building design to limit flood related harm. Denver does both. Indeed, flood risk considerations, which were a great problem in Denver until the 1960s, have guided Denver's urban landscape to an extent that few people realize until they really sit down and consider the issue.

While Denver is relatively disaster free, as major cities go, flood is higher on the risk of likelihood than risks like hurricanes, earthquakes, avalanche, and widespread fire. Tornados and blizzards are probably the only more likely natural disaster to strike the city. Tornados typically have relatively isolated effects. Blizzards in Denver are generally short lived spring phenomena that can simply be waited out. But, floods, when they do happen, often produce widespread devistation. New Orleans was harmed far more by the flooding it suffered than by the hurricane winds themselves.

The areas most at risk of flooding in Denver have been purchased by the city (or in some cases retained by private interests) as green space. The first 15-20 vertical feet of flood plain around Cherry Creek is a bike path that can be periodically flooded. Downtown Denver is buffered from flooding by Commons Park and Confluence Park, and much of the Platte River Valley has also been reserved for bike paths. The Gulch that runs through West Denver is green space. Alamo Placita Park's formal gardens are also a drainage basin to divert Cherry Creek flood waters from the surrounding neighborhood, as is the Denver Country Club. Hungarian Freedom Park buffers much of the S. Speer neighborhood from flooding, while Sunken Gardens Park buffers West High School and the Baker neighborhood behind it from Cherry Creek. A sculpture garden buffers the Denver Performing Arts Center.

Many multi-family and commercial buildings in the Cherry Creek and Platte River basins in Denver are built with ground floor and basement level parking areas, while offices and residences are overwhelmingly on higher floors, a design the minimizes damage in the event of a flood and literally lifts the buildings out of the zone where expensive flood insurance is required. For example, the Parkway office/apartment/condo complex from 11th to 13th on Speer, the Anthem building at Broadway and Speer, and the medical offices to the South of Swedish Hospital near the Platte, are all built on concrete stilts with ground level parking. The REI headquarters had below ground level space, but it is also used for parking. The main structure in the Platte River Valley proper, Elitch Gardens, is not residential and could sustain a flood with only modest damage. Some of the planning is more subtle. Most of the area where Cherry Creek crosses Glendale is buffered with green space. Tamarac Square (about a mile or two East of I-25 on Hampden) is buffered from Cherry Creek by a big parking lot (and the neighboring medical offices limit their basement to parking), which, while not ideal, beats building occupied residences on the first floor right next to the Creek.

This isn't to say the Denver is flood proof. If the first lines of protection in the form of the Chatfield and Cherry Creek reservoirs fail, there will be damage. Most notably, Denver Health, the county's public hospital and a key facility in the event of a major disaster in Denver, has its emergency room doors well within the Cherry Creek flood plain and only limited protection from flooding, in the form of the drainage created by the Speer tunnel under Broadway and Sunken Gardens park. Should the dam on the Cherry Creek Reservoir crack, you can expect to see the Colorado National Guard franticly trying to sandbag along 8th Avenue and Speer to protect the facility. With some advanced planning, the City could build an attractive levy around the location and perhaps even establishing a backup ER entrance on high ground, when there isn't a disaster in progress, to address this risk. While we can afford to have a few houses and businesses flooded and out of commission for months in the unlikely event of a major Cherry Creek flood, a major hospital disabled by such a flood would be a tragedy, so planning for such an unlikely event makes sense.

Another quite vulnerable location is the 9 News building along Speer. TV channels 2 near the Tech Center, 4 on Lincoln Avenue near downtown, 7 near the flood plain but with a 1970s anti-protest design that limits the ground floor to a lobby, and Univision in Capital Hill have largely flood proof headquarters, while the Fox building at 6th and Lincoln and Speer, and public television building in the Golden Triangle are in between. The Cherry Creek mall is also right at the water's edge. Some of the new development in the Golden Triangle neighborhood, like the major new mixed use complex at about 8th and Bannock, also look vulnerable.

In New Orleans, where the majority of the city is in a flood plain, if the first line of defense in the form of the levies fails, rebuilding should take place with a similar attitude. You can build in a flood plain or below sea level area if you are sensible about it. But, a flood plain is a very bad place for ranch style houses, garden level apartments, or any first floor residential or commercial use. New Orleans needs to usher in a new architectural style sensitive to its precarious position in the 21st century, with hat tips to tradition in places like roof lines (perhaps modified to add exit hatches from attics), rather than trying to cling to more pure versions of distinctive French Quarter designs with street level shops and apartments that pose a far higher risk in lower lying areas. Stilts and ground level parking need to be "in" for a very long time in most of New Orleans.

New Orleans also needs to dedictate its most polluted and low lying areas to some form of open space or low human traffic use. It is OK to put a park or ball field or golf course or polo club in a place that has a substantial risk of flooding every thirty years. It isn't wise to put a permanent building that the owner can't tolerate losing there. It is OK to put a scrap yard, or an impound lot on top of an area staturated in toxic chemicals. It isn't OK to put a new elementary school or apartment complex there.

Ironically, golf courses and nature preserves are also actually quite a good brownfields uses (i.e. redevelopment of formerly toxic locations that have been cleaned up to standard of less than perfection). While they get human traffic, the people who use it range over the entire area, limiting exposure to any hot spots that may remain undetected after a clean up, and the people who use it are adults who are unlikely to get their hands and mouths full of potentially toxic dirt, and who are also less vulnerable to pollutants because they not longer in a rapid growth phase. Also, since nature perserves and golf courses are rarely used for hunting, the fauna there are unlikely to end up in the human food chain. Examples of this kind of planning in Colorado are found in the golf courses at Overland Park in metropolitan Denver (once a nationally significant toxic waste site until a EPA brokered plan was reached), the Rocky Mountain Arsenal now becoming a nature preserve, Rocky Flats which is slated to become a nature preserve, and some of the former nuclear waste sites around Nucla, Colorado which are being converted into a golf course (a situation I was involved in tangential litigation over). Similar uses make sense for locations that have been made toxic by spills from the Katrina disaster in New Orleans as well.

While not strictly an issue of city planning, there was also a profound problem with flood insurance underwriting in New Orleans. New Orleans areas protected by Corps of Engineers levies were inappropriately rated as outside the 500 year flood plain where no flood insurance is required. But, levies or not, there is probably no place in all of NOLA that should be free of the requirement of flood insurance in connection with any new mortgage, and flood insurance should be very strongly encouraged among those who don't have it. Indeed, New Orleans would be an appropriate place for the entire community as a whole to purchase flood insurance for the entire city and pay for it through property taxes, freeing the city of the problems of disaster relief funding and of individual property owners who imprudently failed to insure themselves imposing a burden on the process of rebuilding if disaster strikes. This would also allow the City to reduce flood insurance rates with collective solutions to the risk that no one individual would have the power to implement.

I fully confess to not addressing the dicey issues of race and poverty that must be addressed as part of the process of rebuilding New Orleans in the post above. The suggestions I've drawn from the examples above inherently leave less land area for residential use, since essentially I am saying that there are low lying or toxicly polluted areas of New Orleans which should not be rebuilt at all in any residential or commercial way. The building suggestions I've proposed for more salvageable areas likewise would drive up the cost of rebuilding the city thereby reducing its stock of the most affordable housing. Universal flood insurance requirements also drive up the cost of living in the city, making affordable living more difficult.

New Orleans clearly needs to provide a map of a rebuilding plan which produces substantial quantities of housing for people with modest incomes and with the recognition that like any other major city, it needs to be able to sustain some people who are living in poverty. I believe that this can be done, although, of course, New Orleans will never be the same. But, that will have to be the subject of another post.

1 comment:

Dale said...

Andrew,

Congrats on your 1400th post. Whoa.

Minor correction: Overland Park the golf course was never a brownfield. The former Shattuck radioactive waste dump is actually across Santa Fe to the east. And it's just finished getting cleaned up, yea!