Editor’s note: this is the first of a two-part series that focuses on issues directed at the core cause of erosion, namely surface water runoff.

People throughout the Midwest are trying to come to grip with how and why flood events the magnitude of those experienced in 1993 and 2008, as well as other destructive events in between, could occur with such frequency. The probability of two 500-year plus events occurring with this ­degree of severity in back-to-back decades would defy mathematical logic. That is, of course, if they were truly “natural” occurring disasters as some flood experts suggest.

The reality, however, is that these and other chronic flooding events are “cultural” disasters caused by our contemporary urban, suburban, and rural agricultural land-use practices.

It is the opinion of my colleagues and I at Conservation Design Forum that 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 with respect to historical ecological and cultural processes. It is an unfortunate reality that many contemporary urban, suburban, and rural land-use practices are designed and engineered with little awareness or attention to these realities, or the numerous adverse impacts that are directly or indirectly caused by such practices. This lack of awareness is not limited to the ­general public. These processes are not well ­understood by the professional disciplines whose mission it is to protect and preserve our critical natural resources. In fact contemporary engineers, architects, landscape architects, soil scientists, and even biologists and ecologists are actually trained in practices that literally undermine the historical integrity of our precious land and water resources.

In order to better grasp the range and magnitude of adverse affects associated with contemporary land-use practices, including row-crop agriculture, on the stability of local terrestrial and aquatic ecosystems, it is critical to gain an increased understanding of how these systems evolved and functioned historically. As a society, it is imperative that we acquaint ourselves with an understanding of local geology, soils, flora, fauna, hydrology, climate, and the historical cultural influences that helped shape the “nature” of each and every place where we live, work, and play. This knowledge must be coupled with an increased awareness of the many liabilities associated with conventional land-use practices including traditional stormwater-management procedures.

In the following paragraphs, I will provide a basic rationale for how and why such disasters are occurring at a magnitude and frequency that defies logic, and explain why my colleagues and I believe that such events will continue to occur with more frequency and severity with each passing year unless sweeping measures are introduced throughout urban, suburban, and rural watersheds. Since rain falls everywhere, cost effective, ecologically sound solutions must be developed, adapted, and applied everywhere. It is ultimately everyone’s responsibility to learn and participate in this process, although effecting positive change with respect to deeply entrenched conventions as a whole will not be without its challenges.

The good news, however, is that realistic, cost-effective solutions for these problems exist in every environment across the spectrum from urban to rural. We also believe that once the magnitude of the problem is properly understood, coupled with the potential for conversion to sustainable alternatives that not only support the restoration of ecological stability, but economic and social vitality as well, that knowledge will serve as an effective catalyst for change.

Historical ­Patterns
Historically, the terrestrial ecosystems of North America, particularly in the tallgrass prairie ecosystems of the upper Midwest, were very effective at receiving and absorbing rainfall. Very little water ran off the surface of the land. The historical patterns of hydrology throughout the region, and throughout most of the continent, were prevailingly dominated by groundwater hydrology coupled with contributions from direct precipitation. Most natural wetland and aquatic systems including lakes, streams, and rivers were predominantly formed and sustained by constant sources of groundwater discharge, or from surface-water systems derived from steady, stable groundwater discharge. Discharge occurred anywhere along the spectrum from higher to lower gradients, depending on the relationship of geology, soils, surface and groundwater gradients, and other factors. Virtually all of our endemic terrestrial and aquatic species, both flora and fauna, are adapted to such stable patterns of infiltration, evaporation, transpiration, groundwater discharge, consistent hydrology, and stable water chemistry.

The richness and fertility of Midwestern soils owe their properties to the morphology and hydrology of the grasslands, where subterranean reduction exceeded oxidation. Prairie lands, with their deep, water-holding root systems, once stored net amounts of soil organic carbon (SOC) each year in the creation of deep black topsoil. On average, 70-90 percent of a prairie grass’s total mass existed below ground. The root systems could reach or exceed depths of 10 - 15 feet. A typical tallgrass prairie generally contained 15 to 20 thousand kilograms of root mass/hectare, which equates to 12 - 18 thousand pounds of root mass/acre. Each year, approximately one-third of the root system died-off and formed partially decomposed matter that was rich in organic carbon through the process of photosynthesis. Depending on the dryness or wetness of any specific habitat, the average net accumulation rate of SOC throughout much of the region typically ranged from 0.5-2 tons/acre/year. In contrast, annual corn and soybean systems contain, on average, 300 to 600 kilograms of root mass/hectare, and result in an annual net loss of soil organic carbon, rather than a net gain, but more about that later.

Prior to conversion to row-crop agriculture and urban/suburban development, prairie soils on average contained as much as 15 percent or more organic matter. The combination of vegetation cover, fibrous roots systems, and soils with low-bulk density and high, organic-matter content created a regional ecosystem where very little water ran off the 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 groundwater-dominated 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, water-quality 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 water runoff. The force of these combined stormwater flows is focused on a landscape, with its inherent soils, fauna, and flora that evolved with a completely different type of hydrology and water chemistry. The erosive power of this shift in hydrology is impressive. Drainage ditches are gouged into the landscape where no surface drainage existed before. The collective runoff acts to carve out existing streams and rivers, resulting in deeply incised stream banks, subject to constant erosion and sedimentation at rates not seen since the glaciers receded. The loss of infiltration and groundwater recharge in the surrounding watershed, coupled with the depression of normal water levels in the stream system, combine to lower the regional water table, and starve local aquatic systems during dry periods.

On the opposite extreme, intense periods of rainfall, once mediated by a landscape highly capable of absorbing and using the water as a resource, now regularly result in flash floods in areas that were not historically subject to flooding.

The economic, environmental, and cultural impacts of flooding are significant, and often catastrophic.

The instability of streamflow, coupled with degraded water quality, make it difficult for aquatic life to adjust. Desirable species of fish, birds, and other aquatic organisms must struggle for survival in aquatic systems that may experience partial or complete desiccation during dry periods, which happen far more frequently in a landscape and watershed stripped of their ability to cycle water. Such environments exhibit increased water temperature and altered water chemistry, including low dissolved oxygen. Habitat availability becomes critically limiting for many species.

In addition to the temporary detention and eventual discharge of surface water runoff, conventional water resource management approaches often attempt to mitigate flooding at a regional scale rather than where water falls on a site-by-site, sub-watershed basis. Many costly, as well as marginally to non-effective measures such as levies, regional flood reservoirs, deep tunnels, and other massively disruptive flood abatement measures could be downscaled or eliminated, and the money could be directed to substantially eliminate the root problem at its source; runoff.

Unfortunately, once the cumulative volume and force of flood flows reach the main branches of a watershed, no combination of stopgap measures can effectively solve flooding and water quality degradation.

A Vision for Sustainability
In contrast to traditional, stormwater engineering practices designed to direct water away from where it falls, sustainable approaches to site and regional water resource management strives to treat water as a resource, not a waste product. Such measures revolve around the restoration of stable groundwater hydrology on a site- and regional-watershed basis through the incorporation of cost-effective measures that effectively cleanse, diffuse, and absorb water where it falls, thus restoring the historical patterns of groundwater dominated hydrology and water quality. This should be the fundamental design and engineering goal of every type and scale of development project, regardless of whether it is situated in an urban, suburban, or rural environment. Simply put, the degree to which water leaves land in the form of surface-water runoff, is the degree to which the area where it fell in the form of precipitation will be in deficit, and downstream environments will be surfeited, and generally adversely impacted.

There are, however, many practical, cost-effective design and development innovations that are directed at the restoration of hydrological stability and enhanced water quality in urban, suburban, and rural environments. Innovative design and development techniques that bring water’s positive properties to bear, often replicating historical patterns of hydrology, may include one or any combination of technologies that effectively capture, cleanse, recycle, and infiltrate water on-site. In urban environments, integrated-building and site-design techniques such as greenroofs, porous paving systems, bio-swales, rain gardens, and other bio-retention measures, rainfall collection and recirculation measures such as storage cisterns, and the incorporation of deep-rooted, highly absorbent native landscape systems are but a few of the multi-beneficial, cost effective urban water resource management strategies that may be applied.

Such measures are important elements for groundwater recharge, flood reduction, site and regional water quality enhancement, and the restoration of terrestrial and aquatic ecosystem viability.

Another critical component of the historical hydrological cycle that is generally overlooked even by hydrologists relates to the important daily contributions of condensation throughout the growing season. In some respects, native landscape systems were self irrigating in that they had the ability to receive and cycle significant amounts of water as a result of nightly condensation. Water accumulated on the surfaces of plants, worked its way down into the root system, or was stored along the surface of various plants for use by other organisms. One of the benefits of integrated green infrastructure systems relates to their ability to restore opportunities for condensation and daily water cycling to be restored.

Greenroof systems, whether integrated into new construction, or retrofitted into existing buildings, can provide multiple stormwater management, energy-savings, and life-cycle benefits. Whereas typical rooftops generate significant runoff, greenroofs can reduce rainwater runoff by 70 percent or more on an annual basis (Hoffman and Fabry 1998). Even a greenroof with only three to four inches of a light-weight, modified soil mix can regularly absorb many common rainfall events. Greenroofs not only consume rainwater for plant growth but transpire moisture back into the atmosphere.

Throughout many portions of the country, every acre of urban greenroof equates approximately five to eight hundred thousand gallons of water annually that will never leave the roof system in the form of surface-water runoff. Due in large part to their regional stormwater management benefits, many municipalities in Europe and a few in North America offer stormwater reduction credits for greenroofs, or provide grants to facilitate their design and construction.

Porous pavement systems can be designed to infiltrate virtually all of the precipitation that falls on the pavement, and in many applications, absorb significant volumes of runoff that are generated from surrounding impervious surfaces as well. Research indicates that new porous pavement applications can effectively absorb as much or more than 10 inches of precipitation per hour and that although the infiltration rate may damp off after several years, infiltration rates remain in the range of 2.5 to three inches per hour for the life cycle of the pavement system (Borgwardt 1994), (Smith 2001). When used in combination with other site bio-retention measures such as bio-swales, French drains, level spreaders, and dry wells, porous-pavement systems can have a significant positive influence on runoff reduction and water-quality enhancement, even in dense urban settings, and in environments with poorly drained, high-clay-content soils.

Whole systems design solutions which act to integrate building and site functions based upon “green” design principles can generate multiple benefits including the incorporation of sustainable, water-resource management practices. The Blackberry Creek Future Alternatives Analysis (USEPA, IDNR, Kane Co., CDF, 2003) indicates that through proper design, even densely developed industrial, commercial/retail, corporate and institutional, or residential developments can result in the significant reduction of runoff and associated downstream flooding, site- and watershed-scale, water-quality enhancement, the restoration of stable baseflow hydrology to site and regional aquatic systems, and promote aquatic habitat improvements. Numerous studies that have explored the costs associated with conventional vs. sustainable development strategies also indicate that green development is cost effective, both in terms of capital-development costs, as well as the cost of long term goods and services at the community scale. More recently, the downstream cost benefits of green development have been explored and documented (Haugland, et al).

Several highly-urban, mixed-use development projects in Europe and throughout the United States have demonstrated that, through the creative integration of architecture, building and site engineering, landscape architecture, and ecology, off-site, surface-water runoff discharge can be drastically reduced or eliminated (Dreiseitl, Grau, and Ludwig 2001).

Such effective demonstration projects illustrate how rainwater can be collected, cleansed, recycled for heating and cooling as well as gray-water use, and incorporated for esthetic uses within both the building and site.

It is generally our opinion, that density of development is not the critical factor in the generation of runoff and associated water quality problems, but rather the amount of effective imperviousness that is the primary contributor of runoff. There is no doubt that a strong correlation exists between density and water quality degradation in urban environments that are subject to conventional development practices. It is quite possible, however, to effectively reduce or eliminate this problem even in the most urban environments through the incorporation of creative, water-resource management strategies. SLDT