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  • Chris Allan


In September 2013 the Boulder area saw almost a year’s worth of rain fall in 5 days. Creeks raged, streets were flooded, houses were washed away or damaged. Four lives were lost in the county.

Yet it could have been so much worse. Smart spatial planning over many years kept buildings and people out of many floodplains, so raging creeks were able to flow over undeveloped areas at a far reduced cost to property and lives.

The City of Boulder alone has 42,000 acres (17,500 hectares) of Open Space – land that is set aside by the City, where no building takes place. The Open Space program has three goals:

  • Provide opportunities for outdoor recreation

  • Conserve local biodiversity

Provide outlets for flood mitigation.

The first two of these goals are met every day. But for many the value of the third goal was not evident until they saw the water washing over open fields rather than residential neighborhoods. There was still considerable damage: fences, gates, trails and other structures in Open Space were destroyed all over the city, and the cost to repair them will be in the millions of dollars. However, this cost is far lower than it would have been had these areas been developed with houses and businesses.

These three goals are often in conflict: recreational users bump up against the need to close areas during raptor breeding seasons; restrictions on dogs often frustrate others who want their animals to romp free in the outdoors. Yet, the three distinct services provided by Open Space create a wider constituency of support – Boulder voters have been taxing themselves to buy and maintain Open Space since 1967.

The Open Space role in flood mitigation is clearly evident in the aerial photo below. South Boulder Creek flows through Open Space along the Bobolink Trail, a popular spot with runners, dog walkers, bird watchers, and cyclists. During the deluge, the creek overflowed its banks and spread across the land on both sides. Because there were no buildings in the area, the water flowed freely with minimal damage to property and people. But when the water reached the edge of the Open Space property at the top of the photo, houses in that neighborhood were badly damaged. The water continued to flow, but now it flowed through living rooms and not over pasture. Some houses in the area had been built on raised grades, and these fared well in the flood. But many others became part of the river.

Above: Aerial photo showing where flood waters overflowed into Open Space and then a residential neighborhood. Photo credit: Chris Allan (ISET-International)

Above: South Boulder Creek spilling over into Open Space on the Bobolink Trail. Photo credit: Chris Allan (ISET-International)

Even though this neighborhood at the end of the Open Space was hit by the flood, the damage could have been even worse. Pre-planning by the City and County reduced the some of the damage there. Some of the flooded houses in this area were built in the 1950s, and until 2010 most were not connected to the City water or sewage lines. At that time, local government officials worried that a neighborhood with septic tanks and well water in a major floodplain was a risk to public health. So in 2010, the County and City pushed residents to annex their neighborhood into the City in order to hook them up to City water and sewage. When the neighborhood flooded in 2013, the houses were damaged, but there was no contamination from water or sewage. Threats to public health were avoided.

However, the neighborhood just downstream — which had declined to annex itself to the city in the past — did experience contamination in its well water for months after the flood. Boulder City Planner Chris Meschuk was quoted in the local newspaper about annexing this second neighborhood: “The interest is a lot higher.…When we met with the Old Tale Road residents, some of the people who invited us had not previously been interested in annexation, but because of the flood, their perspective had changed.”

The vast majority of the time City of Boulder residents benefit from the recreation and conservation opportunities that Open Space provides. And, for those rare occasions when floods threaten the city, Open Space also provides a critical safety valve for raging creeks.

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