Agenda - Planning Commission - 02/01/2007

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ASK THE AUTHOR JOIN US ONLINE! About the Author Lisa Nisenson is a principal at Nisenson Consulting, She is also working with Tetratech to develop stormwater program guidance for the U,S, Environ- mental Protection Agency's Office of Water, Nisenson has worked Oil smart growth at the national and local levels for nearly 15 years, Go online from December 18 to 29 to participate in our "Ask the Author" forum, an inter- active feature of Zoning Practice, Lisa Nisenson will be available to answer questions about this article, Go to the APA website at www,planning,organd follow the links to the Ask the Author section, From there, just submit your questions about the article using an e-mail linlc. The authors will reply, and Zoning Practice will post the answers cumulatively on the website for the benefit of all subscribers, This feature will be available for selected issues of Zoning Practice at announced times, After each online discussion is closed, the answers will be saved in an online archive available through the APA Zoning Practice web pages, conveyance system as quickly as possible. The approach kept basements and foundations dry but proved catastrophic for local streams that suffered the impact of collective polluted flow from houses, offices, and parking lots. The damage to streams is more than an environmental misfortune. The flow collected from acres of concrete scours riverbanks and creates mud deposits, making streams wider and shal- lower. The altered water flow poses challenges to floodplain managers, water supply companies, and industries that rely on clean, steady flows. The primary reason for the problem is the location and extent of land development, and the most common indicator is impervious cover-rooftops, parking lots, and roads, and even compacted dirt, gravel, and grassy surfaces. WHAT DRIVES IMPERVIOUS SURFACE? Watershed managers and land developers cannot manage the impacts of excess impeNi- ous surface without first understanding the reasons for its proliferation. Planning and zon- ing officials regularly make decisions about impeNious cover with respect to: · Parking. Minimum parking standards and cautious lending practices can lead to unnec- essarily large parking lots. · Site design. Site design parameters have increased with setbacks and minimum lot size requirements (partially to accommodate more parking) and maximum height limitations that force development outward to meet demand. Even where codes allow'multistory development, parking requirements based on square footage ultimately dictate less intensity. · Street design and mode choice. Uncon- nected, hierarchical street designs often result in dispersed development and an increase in impeNious surface, leading to poor trans- portation choices. Street design also influ- ences mode choice. In places where trips for daily needs cannot be made without a car, businesses will argue that they need gener- ous parking allotments. · Separation of uses. The Euclidean model of separating uses can make walking or combin- ing trips impractical, if not impossible. When businesses and services are spread out, more impervious surfaces are created and people are beholden to vehicular travel. · Redevelopment. Redevelopment is among the best (yet least recognized) watershed pro- tection strategies. By contrast, vacating an urban site to relocate at the basin's edge ulti- mately means the watershed is burdened with runoff from two sites. · Infill. Infi.ll development was listed in the 1999 notice as a viable strategy for reducing stormwater impacts. This was mostly true. However, planners must track absorbent spaces that are poised for development and balance flows accordingly. . New stormwaterrequirements. Some ofthe emerging BMPs require that large portions of a site remain undeveloped (though not nec- essarily undisturbed). Be careful. The result can favor developers who assemble a parcel large enough to accommodate 200,000 square feet of floorplate. 800 parking spaces, drive aisles, and service bays, plus the calcu- lated land' set-aside. Such requirements tend to exacerbate sprawl and impeNious cover because big enough parcels can only be found in the outlying areas and require the expansion of roads and other infrastructure. THE ROLE OF PlANNING AND ZONING Planning and zoning departments can have a big impact on the development and mainte- nance of stormwater management plans. The question is where to start. First, establish which federal and state stormwater rules apply, in particular, for post- construction. Among the first questions to ask are (1) What water quality problems exist today? and (2) What ~re the anticipated prob- lems in the watershed?The type and nature of water stressors invariably influence planning needs. Also, obtain copies of the comprehen- sive plan and watershed plan. A strong compre- hensive plan is the initial and most important BMP to put into place. Applying BMPs in an ad hoc ~anner will not protect against stream degradation and flooding in the long term. Ignoring a land-use pattem that creates excess imperviousness will only delay the inevitable costs of stream restoration and flood clean-up that site-specific BMPs cannot control. ZONING PRACTICE 11.06 AMERICAN PlANNING ASSOCIATION I P'4es