Sustainable Land Development Today - March 2009 - (Page 10)

SLDT FINANCE EROSION CONTROL The Solution is in the Land By James Patchett, ASLA, LEED AP Major flood events can be traced to land-use practices, including modern agricultural methods. Editor’s note: This is the second of a two-part series that focuses on issues directed at the core cause of erosion, namely surface water runoff. he occurrence of flood events such as those that have ravaged the Midwest—most notably the two, 500year floods in 1993 and 2008—were not “natural” disasters, as some contend. These, as well as other cases of chronic flooding can be directly connected to contemporary urban, suburban, and ruralagricultural, land-use practices. Long-term solutions to chronic problems associated with water must address land-use practices that extend beyond urban and suburban environments into the predominantly agricultural watershed. If cost effective, ecologically restorative solutions are not incorporated into agricultural environments, river communities will continue to be subject to frequent, costly flooding no matter how many flood reduction or protection measures are implemented within their municipal boundaries. Problems associated with increased runoff, erosion, sedimentation, flooding, aquifer depletion, water quality degradation, loss of habitat and biodiversity, and even climate change, exist in large part due to a fundamental lack of awareness of historical ecological and cultural processes. Many contemporary urban, suburban, and rural land-use practices— designed and engineered by professionals and accepted by the general public—produce adverse effects due to a lack of awareness of natural process which would mitigate such disasters. It is imperative that we understand local geology, soils, flora, fauna, hydrology, climate, and the historical cultural influences that helped shape the “nature” of every place where we live. The fact is that T there are realistic, cost-effective solutions for these problems across the spectrum from urban to rural locales. The Agricultural Dilemma It has become better understood that contemporary urban and suburban landuse practices cause substantial runoff, flooding, and water quality degradation. It is far less understood, however, that conventional row-crop tillage practices also contribute significantly to site and regional water resource management problems, including the increased generation of surface-water runoff and flooding; water-quality degradation from chemical and sediment pollution; and the contamination and depletion of surface and groundwater reserves. Row-crop commodity agriculture has also proved to be economically unsustainable without massive federal and state funding programs. Declining revenue, even in the corn and soybean biofuels boom, coupled with the increased loss of soil fertility and topsoil resources, has resulted in an economic “no-win” situation for many local agricultural producers. Tillage exposes highly organic soil to the atmosphere, promotes oxidation of accumulated soil organic carbon, which in turn reduces the soil’s tilth and its capacity to absorb rainwater and hold nutrients. The loss of a strong, perennial ground cover exaggerates the rate and amount of soil loss to wind and water erosion. After several years of repeated tillage, the onceextensive root system of prairie vegetation disappears altogether and a once highly organic soil becomes primarily mineral in composition. Compaction and loss of root structure and organic-matter content alters soil density causing water infiltration rates and capacity to drop dramatically. Introduction of drainage tile acts to accelerate the rate of water loss, oxidation, and depletion of soil nutrients. In turn, crops need significant additional resources to grow including fertilizers and water. The impact of fertilizers, herbicides, and pesticides in our soil, and surface and groundwater systems is well documented, but other negative influences associated with annual, row-crop tillage are far less understood. A 1990 USDA Soil Conservation Service (SCS) later changed to the Natural Resources Conservation Service (NRCS) study concluded that, of the original average 18 inches of topsoil across the state of Iowa at the time of settlement, ten inches had been lost to wind and water erosion, and that half the tilth was gone from the remaining eight. The long-term consequences on both the local and broader economy are frightening particularly in light of current conditions where many acres of Iowa farmland have lost all, or nearly all of their topsoil, and the average organic matter content of many Iowa soils is two percent or less. Once the organic matter levels are this low, coupled with altered soil structure, the land appears to have reached a critical “tipping point” with respect to its inability to absorb and hold water. We believe that this a primary reason for the increased frequency and magnitude of flood events. As the water in the soil is drained away, the reduction/oxidation relationships change dramatically. Whereas once the prairies held their water, and carbon was 10 March 2009 Sustainable Land Development Today

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

Sustainable Land Development Today - March 2009 Contents Our Voice: Energy Savings Accounts Mining the Sewers for On-site Reuse Modern Flood Disasters The Financial Challenge of Leed® Technology: Opportunities Exist to Buy in Now SLDI In Focus: A Look Inside Calendar of Events Energy: Solar Power on Rails Industry News Products & Services The Bottom Line: Green Lending – Class G Advertiser Index Editorial Board SLDT Resources Last Word: Not All Gloom & Doom

Sustainable Land Development Today - March 2009

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