Sustainable Land Development Today - February 2009 - (Page 7)

surface of the land. Most rainfall either transpired through the living tissues of hundreds of different species of plants or seeped through the ground at a constant rate, only to discharge finally in fens and springs far from where it fell. Surface water runoff and accumulation in local streams and rivers occurred in spring snowmelt when the ground was frozen. Once the ground thawed, however, and the plant systems sprang back to life, very little to no water ran off the surface. Growing season floods comparable to the frequency and magnitude that we suffer today in late spring and summer would have been extremely rare if not impossible to have occurred. No matter how hard the rain, the prairie was very effective at absorbing the rainfall, and the region’s wetlands, streams, and rivers remained very stable throughout the growing season both in terms of water levels, and water chemistry. Water Quantity and Water Quality Impacts Most of our contemporary-infrastructure and conventional-planning methodologies are products of a contrived, visual aesthetic with little understanding, relationship, or grounding in the unique realities of place. They represent a cultural indifference to the function of historical systems, or even the energy required to maintain this infrastructure, much less any long term consequences. As a result, contemporary, land-use practices have drastically altered the historical patterns of stable groundwaterdominated hydrology and associated water quality. Today, nearly all environments are instead dominated, and in most cases negatively impacted, by erratic forms of polluted, surface-water runoff. Conventional water resource engineering practices are generally directed at the collection and conveyance of stormwater runoff through enclosed storm-sewer systems that generate concentrated points of discharge with an associated volume and velocity of flow that is extremely difficult to mitigate. The underlying goal is to remove water from where it falls as quickly and efficiently as the law will allow. All of our education, creativity, and practical experience are embedded in a doctrine of collection and conveyance, where water is treated as a waste product rather than a resource. Most communities have adopted stormwater-management codes and ordinances, nearly all of which are directed at the temporary storage and controlled release of virtually all collected stormwater runoff. This approach is nearly always in violation of the historical laws of hydrology as governed by the physical characteristics of the watershed including its soils, geology, flora, and other factors described above. The temporary storage of surface runoff in conventional stormwater detention systems often exacerbates downstream flooding, waterquality degradation, and habitat loss due to the cumulative volume and velocity of discharged flows. Once removed, the discharged volume acts to inundate downstream environments, while robbing the local watershed of infiltration and the historical processes of recharge that maintained the stable baseflow hydrology necessary to sustain the physical and biological integrity of site and regional aquatic ecosystems. In typical urban and agricultural environments, aquatic systems including wetlands, lakes, streams, and rivers often experience rapid fluctuations in hydrological velocity and volume, generated almost completely in response to surface Circle 103 or www.SLDTonline.com/webcard www.SLDTonline.com 7 http://www.stormchamber.com http://www.stormchamber.com http://www.SLDTonline.com/webcard http://www.SLDTonline.com

Table of Contents Feed for the Digital Edition of Sustainable Land Development Today - February 2009

Sustainable Land Development Today - February 2009 Contents Our Voice Modern Flood Disasters Origin of the Sustainability Movement SLDI in Focus Calendar Build Smart Product Innovation Takeoff and Cost Management Industry News Products & Services Advertiser Index Editorial Board SLDT Resources Last Word

Sustainable Land Development Today - February 2009

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