Conquent: Without Limits
Land Use Planning Division

John Bissell & Associates

The relationship between Environmental Protection, Population Density and Work Specialization

By John Bissell
Posted: 2009-02-13 21:18:13

Land Use Planners and Environmentalists have known for some time that running over our rural land with low density housing creates significant impacts to both the natural and man made environments. In 1965 the State of California passed legislation requiring Cities and Counties to plan, and in the same year passed the Williamson Act or the Land Conservation Act to preserve farm land from conversion to other uses. In 1969 Oregon passed similar legislation, and in 1973 increased the power and scope of the land use planning requirements to establish Urban Growth Boundaries. In 1990 Washington State passed the Growth Management Act mimicking (to some degree) the 1973 Oregon legislation.

The point of this history is to establish that we have known for sometime that one of the biggest threats to our environment is urban sprawl. Low density development requires more land for the same activities that would take place in higher density development. And by taking up more land, the transportation options become more limited. It’s harder to make mass transit work, and walking and biking are left only for the dedicated athlete. So we are left to single occupancy vehicles – cars. Those cars then have to drive farther to accomplish the same task as compared to the higher density. And not only that, we need to create more roads using more asphalt to get anywhere, thus increasing our impervious surfaces, which runoff into our streams brining the oils and rubber deposits with the water and so on, while increasing flooding and erosion problems.

To sum up – in a low density model, we must use more roads, to travel farther burning more oil, putting more greenhouse gasses in the air while causing more flooding and destruction to streams and rivers. But that’s old news. Note the 1965 California rules, and even the newbie in this regulatory area- Washington came on board almost 20 years ago.

Several studies have been done that assert the best minimum density to resolve these issues. These minimum numbers usually range from eight to twelve dwelling units (d.u.) per gross acre. In this context, “gross acre” means that if you measure say one square mile (640 ac.) there should be between 5,120 and 7,680 – regardless of how many shopping malls, parking lots, office or parks are also in that square mile.

But while we’ve studied the need for density on one track biologists have been studying the natural environment in our urban areas. What we have learned is that streams, wetlands and other habitat areas are incredibly important to the entire ecosystem, from fish – to eagles to humans. If the stream is not protected, the stream is polluted with sediments, oils, heavy metals, fertilizer and so on. The sediments will eventually fill in the wetlands. Or in a more extreme situation, the wetlands are filled by development, and the stream is placed in a pipe, all wildlife associated with the stream is thus removed. This has been a contributing element to the substantial reduction in the fisheries near most metropolitan areas. And this in turn affects bird life and on up the food chain.

The elimination of the wetlands compounds these problems. Wetland create bird habitat and fish rearing, and places for the bugs that the wildlife eats to hatch. But the wetlands also slow the water in the streams, reducing erosion and flooding, while cleaning the water.

There are a number of studies that help us know what to do about the protection of stream and wetlands. Any particular stream or wetland or ecosystem can be rated by a trained biologist. Depending on this rating, certain buffers can be established around the stream or wetland. There are other things that can be done like replanting the riparian (next to the stream) area and adding fish shelters like tree stumps to the stream course, but the primary mitigation recommended by these studies is to keep development and people away from the stream.

So what’s the problem? We have strong legislation effecting change to the urban densities, and in most states there are strong rules requiring protection of the streams and wetlands. Shouldn’t this be enough?

Well, no it’s not - and here’s why: New studies are showing that larger buffers are needed to protect the natural environment. Those larger buffers are adopted into the state and local development rules. Since the Pacific Northwest is a rainy environment, the landscape is riddled with small streams and wetlands. Thus the area removed from potential development in the Urban Growth Area is significant. These new rules are not coordinated with the zoning requirements to make sure that the minimum density continues to be achieved after the larger stream and wetland buffers are established.

In fact, the jurisdictions are resistant to the appearance of high density – taller buildings closer together. In response, these jurisdictions have required the density of a development to be capped, and to measure the density based on a net calculation that deducts environmentally critical area and their buffers. Thus a development that notes ten dwelling units per acre on the plans, may really have five or six dwelling units per acre when looking at the gross lot size, and only have three or four gross units per acre when it is looked at in context with the neighborhood.

This gets to the question: Are we hurting the environment by requiring larger buffers? By implementing large stream and wetland buffers we use up a significant amount of land within the urbanizing area without adjusting our zoning rules to compensate. This reduces the amount of land available for development, thus filling up the urbanizing area faster and putting pressure on the Urban Growth Boundaries. The Boundaries are then expanded, and sprawl continues creating new impacts in the rural area that could have been avoided if the zoning had been coordinated with the environmental legislation.

Clearly there is a trade off to be made here. Right now the trade off is that we allow more sprawl for the purpose of protecting localized streams and wetlands. Is that the right trade off? No one has studied this question, so we don’t know. We are only making this choice by default. “Is the environmental regulation protecting streams creating a bigger impact to the streams because it is effecting urban sprawl?” Without an answer to that question, there is no way to know if we are doing good or harm.

There may be solutions to this dichotomy. It may be that the theory is right, and that large buffers really are the answer, but that the large buffers cannot be enacted without sharp increases in allowed density building height. However the answer might be that we study drainage basins and then choose to stop trying to save streams that are deep in the urban area, and have little chance restoration. Again without a study to determine the impacts to the environment created by the reduction of land in the urban area we can’t know and our regulations continue to shoot in the dark.

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