It is common for Smart Growth proponents to claim that adding density to existing urban infrastructure is cheaper than building infrastructure in new areas. The reality, however, is more complicated. The 11/23/09 New York Times reports:
As Sewers Fill, Waste Poisons Waterways
In the last three years alone, more than 9,400 of the nation’s 25,000 sewage systems — including those in major cities — have reported violating the law by dumping untreated or partly treated human waste, chemicals and other hazardous materials into rivers and lakes and elsewhere, according to data from state environmental agencies and the Environmental Protection Agency.
But fewer than one in five sewage systems that broke the law were ever fined or otherwise sanctioned by state or federal regulators, the Times analysis shows…
As cities have grown rapidly across the nation, many have neglected infrastructure projects and paved over green spaces that once absorbed rainwater. That has contributed to sewage backups into more than 400,000 basements and spills into thousands of streets, according to data collected by state and federal officials…
…academic research suggests that as many as 20 million people each year become ill from drinking water containing bacteria and other pathogens that are often spread by untreated waste…
“The E.P.A. would rather look the other way than crack down on cities, since punishing municipalities can cause political problems,” said Craig Michaels of Riverkeeper, an environmental advocacy group. “But without enforcement and fines, this problem will never end.”
…New York’s system — like those in hundreds of others cities — combines rainwater runoff with sewage. Over the last three decades, as thousands of acres of trees, bushes and other vegetation in New York have been paved over, the land’s ability to absorb rain has declined significantly…
New York’s sewage system overflows essentially every other time it rains…
…unless cities require private developers to build in ways that minimize runoff, the volume of rain flowing into sewers is likely to grow, environmentalists say.
The only real solution, say many lawmakers and water advocates, is extensive new spending on sewer systems largely ignored for decades. As much as $400 billion in extra spending is needed over the next decade to fix the nation’s sewer infrastructure, according to estimates by the E.P.A. and the Government Accountability Office…
Our Column in Today’s Gazette: The Hidden Risks of ‘Smart Growth’
Besides hoping that people will stop driving, another critical assumption of smart growth advocates is that it’s cheaper to add density to existing urban infrastructure than to add infrastructure to new areas. Harvard researchers Alan Altshuler and Jose Gómez-Ibáñez find that the reverse is true. Portland, for example, needs a multibillion-dollar consolidated sewer outflow system to manage surface water accumulations from its dense development and the spread of impervious surfaces.
Randal O’Toole: “The Folly of ‘Smart Growth'”
The New Draft Sustainable Northampton Plan: Balancing Compact Growth Against Taxes, Urban Greenspace, Homeowner Preferences
Mishandled campaigns for density can trigger an intense political backlash. In suburban Portland, voters recalled a mayor and two council members over dense development and a neighborhood light-rail alignment (Farris, p.23). Farris, an Associate Professor in the Department of Planning and Landscape Architecture at Clemson University, recommends a smarter Smart Growth approach that takes into account the facts on the ground and citizen preferences:
…smart growth advocates should be realistic about the amount of development that will occur in built-up areas versus outlying open land as various stakeholders consider future policies. The U.S. population is expected to double in this century. It is hard to imagine that a large percentage of that growth will occur in existing built-up areas.The Sustainable Northampton Plan calls for a minimum of 50% of all new housing developed in the city to be infill. (p.17) The Farris analysis suggests this goal may be aggressive, unrealistic, and likely to invite substantial resistance from current residents.
Smart growth advocates should focus especially on encouraging higher-density quality development on open peripheral land. The discussion in this article suggests that this is where most development will occur. Perhaps up to 20 percent can be infill in cities and the older suburbs (this would be a big increase from present patterns). The density of most cities is 5 to 10 times that of their suburbs (Downs 1994)…
Perhaps Downs (1994) best describes the scale of infill development necessary to accommodate growth when he shows that
to raise overall density from 3,500 to 7,500 persons a square mile, 47.1 percent of all housing land would have to be redeveloped with new housing at fifteen units per acre, 24.2 percent at twenty-five units an acre, or 14.0 percent at forty units an acre. Clearly, any substantial increase in the residential density of built-up areas that is to be achieved through redevelopment would require major clearance and rebuilding. This would be a major disruption to existing neighborhoods… It is hard to believe that residents where such upzoning is planned would permit it, considering the pressures they have exerted in the past…Many suburbs today are built to accommodate between 1,000 and 3,000 people per square mile, typically based on markets and land cost (Downs 1994). While infill will continue in selected submarkets, smart growth advocates should aggressively pursue higher-density, quality development at the periphery rather than the typical low-density suburban sprawl of the past 50 years (Danielsen, Lang, and Fulton 1999). (p.26-27)
Northampton’s Flood and Natural Hazard Mitigation Plan: Wetlands Buffers of 100 Feet Are an Effective Flood Mitigation Strategy and Should Be Consistently Enforced
One great misunderstanding is the belief that floods only happen in the floodplain. With sufficient rain, almost any area will experience at least pockets of surface flooding or overland flooding… Heavy rain in the more urbanized parts of the City with extensive paved and impervious surfaces can easily overwhelm stormwater facilities resulting in localized flooding and basement damage. Stormwater flooding also contributes to water pollution by carrying silt, oil, fertilizers, pesticides and waste into streams, rivers and lakes. As the intensity of development continues to increase, Northampton will see a corresponding increase in serious stormwater problems. It is therefore important that the City as a whole, not just residents of the identified floodplain, address the need for mitigation…
Tree Loss and Slab-on-Grade Foundations: A Poor Fit with the Sustainable Northampton Plan
A single large tree can remove as much as 150 gallons of water from the soil each day. They also intercept a portion of rainfall before it reaches the ground.
EPA: Wetlands and Flood Protection
Wetlands within and downstream of urban areas are particularly valuable, counteracting the greatly increased rate and volume of surface-water runoff from pavement and buildings…
A one-acre wetland can typically store about three-acre feet of water, or one million gallons. An acre-foot is one acre of land, about three-quarters the size of a football field, covered one foot deep in water. Three acre-feet describes the same area of land covered by three feet of water. Trees and other wetland vegetation help slow the speed of flood waters. This action, combined with water storage, can actually lower flood heights and reduce the water’s destructive potential. (Source: EPA)
As Hurricane Threat Builds, Has Complacency Set In about Flooding?
Infill sounds great on paper, but when it means paving over green space in downtown Northampton, it runs contrary to sound flood mitigation practice. The reality is that much of the remaining green space in downtown is in low-lying areas that are most susceptible to flooding. It makes sense to go along with the collective wisdom of the past 350 years and leave them undeveloped.