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Returning to the Natural Stormwater Management Approach

By Mark Hieber

A look at history provides a glimpse to a better future.

A verdant, park-like low forest, stretching west for 1000 miles…that’s how  the eastern half of North America appeared prior to European settlement. At that time, Native American Indians managed the vast forests and prairie and savanna meadows by burning off the deeply rooted grasses and wildflowers on the ground plane every autumn with fire.

These frequent, low intensity fires shaped the landscape, while preserving the trees. The appearance to the early Europeans resembled a well maintained park in Europe, with massive, high-branched, virgin, old growth trees towering above a shadedappled flowering ground plane. It was said that a squirrel could climb a tree at the shore of the Atlantic Ocean and never set foot on the ground until reaching the Mississippi River.

This natural system of large canopy trees and deeply rooted prairie and savanna plants was the backbone of an infiltration-based hydrology model that minimized overland flow of stormwater. The stormwater and snowmelt that did reach the ground was allowed to percolate into the ground, traveling horizontally below the ground for periods of days, months, and even years before slowly seeping into wetlands and streams at a constant temperature in the low 50-degree Fahrenheit range. This cool water provided the ideal habitat for many of our native aquatic and semiaquatic plants and animals.

Historical information regarding the Mississippi River from that pre-settlement period indicates that the river’s flood stages were significantly less drastic than they are now. Trees, prairies, and wetlands moderated flows. At that time, the “Big Muddy” – a term referring to the now heavily sediment-laden river – flowed much clearer.

For the last 300 years or so, the American landscape has seen constant change.

While only 4.8% of the land area in the United States is developed, in many instances land clearing for farming and urban development has turned once gently flowing streams with little erosion, into flashy, raging torrents that carry away enough sediment to cover the State of Rhode Island two inches deep each year as the Mississippi River delta accelerates its growth into the Gulf of Mexico. We have lost the infiltrationbased hydrology that has created the landscape in which we live. We can try to fight nature, but nature will always win.

The increasing pace of urbanization, has completely changed the natural systems that have governed the landscape for thousands of years. Along with deforestation, topsoil that supports native species has been stripped. The remaining subsoils have been compacted to such densities that their stormwater infiltration capacity is reduced to the equivalent of pavement. Surfaces have been sealed with asphalt and concrete, often leaving only token remnants of green spaces within which we place one or two orderly, lollipop shaped trees with some turfgrass beneath. The incredible diversity of our native plants has been traded for a few sterile, imported species of trees and shrubs. And to date, we’ve considered this to be “progress” and we’ve called this “not too bad”.

Every location in this country is unique. Each has a specific combination of climate, orientation, soils, geology, rainfall, flora and fauna. Therefore, every location should be considered a special “Place”. The price we pay for decimating this Place where we live is high. With urbanization and the loss of tree cover, we are seeing an ever-increasing risk of significant flooding problems. In many jurisdictions, combined sewers that carry both stormwater and raw sewage are overwhelmed, spilling their polluted contents into our lakes and streams. According to Roger Pielke Jr., director of the Center for Science and Technology Policy Research at the University of Colorado’s Cooperative Institute for Research in Environmental Sciences, flooding cost the United States approximately $50 billion in damages during the 1990s alone.

The Present
Most of today’s environmental regulations actually encourage us to do “bad”.

With stormwater, our ordinances frequently require – and we therefore design for – the direct and speedy discharge of stormwater across pavements and hot roofs into engineered pipes that carry warm, polluted and sediment laden water into our creeks and streams. This water degrades the habitat of our native aquatic and semiaquatic plants and animals. No longer able to thrive, native plants give way to exotic species, such as Phragmites, an invasive plant and one of only a few that can survive in warmer, sediment laden, polluted creeks and wetland areas that experience wildly fluctuating water levels.

All of us in the land development industry realize that the answer to these issues is not to stop development. Society continuously demands that we meet its ever-evolving needs. In doing so, we fulfill important roles for today’s society – and future generations to come.

Changing needs require that we change in kind. Today’s realities dictate that we be effective gatekeepers for the future.We can – and must – incorporate the best of today’s world with our scientific knowledge about history to reflect a new view. Urban areas can be entwined with surrounding ecosystems in ways that are mutually enriching.

To be sure, there is resistance to overcome. Many believe that the interests of commerce and the environment are inherently conflicting. Environmental strategies are often seen as being at odds with land development economics. As an industry, in order to effectively fulfill our role in society, we must increase our level of sophistication in this area.

Today’s reality is that we must develop our land in ways that, rather than seeking to do “less bad”, we strive to do “more good”. We are in the era of restoration. We cannot continue decimating our natural systems at the current rate. We must reverse the trend and begin to bring nature back.

Reforestation of our watersheds is the single most important thing we can do to start to do more good.

Economics and the Environment Work Together
People’s attraction to natural features is high. Mature trees on residential properties frequently can add 20% or more to the value of a home. Homes with mature trees sell faster than those that do not have mature trees. Mature trees, by their shading and evapotranspiration characteristics, can significantly reduce summer energy requirements for cooling buildings and homes. Evapotranspiration sends moisture back into the atmosphere and is part of a tree’s process for generating energy through photosynthesis.

In healthcare settings, patients in rooms with views of green spaces featuring trees have been shown to get better faster and require less pain medication during recovery. Imagine how much money could be saved in medical insurance if all rooms had a view of green spaces. In office settings, it has been demonstrated that workers are more productive when they have views of green space and trees. And yet, we often see trees indiscriminately taken down and surfaces sealed with pavement because the trees and green areas are in the way of efficient earthwork, or utilities, or excessively wide streets that are dictated by engineers who are mandated to move traffic “efficiently”.

Above and beyond real estate value, reforestation provides tremendous additional benefits. Consider stormwater and the amount of resources we commit to controlling it, and the insurance we pay to repair the damage from flooding.

A Home in the Wilderness - (Sanford Robinson Gifford - 1866) - The dense old growth forest in the background contrasts with the empty foreground, dotted by several tree stumps cut by man who utilized the wood to build a home. Clearing the land by European settlers marked the beginning of the threat to the sustainable landscape managed by natives American for thousands of years. Courtesy The-Athenaeum.org

Science has given us a much better appreciation for the significant role that trees and other vegetation play in stormwater management. The considerable surface area of a tree – its leaves, branches, and fissured bark – creates an enormous surface area that catches and holds rainwater. Tree roots absorb water and send it back into the atmosphere.

According to studies done at the Institute of Environmental Planning at the Technical University of Berlin, a mature tree captures at least 80% of all precipitation that falls upon it. This water never leaves the vicinity of the tree as runoff. Instead, it is evapotranspired back into the atmosphere.

Each of us has experienced this rain catching ability of trees while walking in a wooded area in the rain. The forest floor tends to be dry during shorter duration cloudbursts while water covers leaves and soaks into bark surfaces. According to rainfall data, most rainfalls are light or of shorter duration. During longer or harder rain events, some rain finds its way to the ground after the leaves and bark are saturated. This water infiltrates into the ground where the tree’s root system takes the water into the tree. Approximately 90% of a mature tree’s roots reside in the upper 18″ of soil and typically spread well beyond the dripline of the canopy.

Because of trees and a forest’s uncompacted soils, 90% of all precipitation in a virgin forested watershed area never leaves the site, while 10% finds its way as stormwater to areas beyond the forest. By contrast, only 10% of all precipitation in urban areas remains on site, while 90% is discharged, usually as fast as possible, into nearby creeks and streams.

The Future
What is needed now is a fresh understanding of how our natural setting can be improved. To affect change, a suitable area must be defined. Using a watershed as a defining area is a good target.

Watersheds are areas, defined by topography, that generally direct stormwater to a major stream or river. Within a watershed there can be many sub-watersheds that contribute stormwater to creeks that, in turn, contribute water to the major stream or river. Watersheds do not recognize the jurisdictional boundaries that have been overlaid upon them. Cities, townships and counties typically each have their own sets of rules on how to handle stormwater. Many dictate the speedy removal of water from the places where it lands, quickly sending it to local streams. Most municipalities have few if any requirements about maintaining or increasing tree cover. This is a missed opportunity.

Precisely what is needed is a holistic watershed policy, across jurisdictional boundaries, that governs how stormwater will be handled and what measures can be done to “do more good” through application of new development policies and retrofitting (retro planting) existing urban areas.

 
 
 

Courtesy of The Rouge River Project

A Case Study
The Rouge River Watershed in southeast Michigan is a good example to review. The watershed is approximately 438 square miles in size and includes all or part of 48 municipalities in three counties, with a population of over 1.5 million. Each municipality and county has their own set of requirements. Some have combined sewers. Some do not. None have ordinance requirements that apply innovative techniques for managing stormwater. None have requirements for reforestation as a tool to manage stormwater. More than 50% of the watershed is considered urbanized, mostly in the south and east portions.

The years of 1850-1940 were characterized by immigration, industrial development, and rapid urban growth. However, it was this development and growth that led to the first forms of river pollution. To deal with the increase in population, sewer pipes were built to carry sewage and stormwater which emptied directly to the Rouge River. Similarly, industrial wastes were poured, buried, or dumped in the most convenient location, which was often adjacent to or in the river.

The construction of the Ford Rouge Complex during World War I proved to be a defining moment in the river’s history. This facility grew into the largest industrial complex in the world with support industries up and down the adjacent riverbanks. In the 1950s and 1960s it was said that the Rouge was so polluted that it would catch on fire.

Within the watershed, here are a few organizations currently seeking to “do more good:”

The Ford Rouge Visitor Center
This adaptive reuse for part of the Ford Rouge center has created an interpretive venue that will be the first stop on the Automobile National Heritage Area Tour. Ford Motor Company worked with HarleyEllis and other experts in the field of “green” industrial development to create concepts for this project and the remodeling of the entire Ford Rouge Center.

Lawrence Technological University (LTU)
LTU has recognized the benefit to the community and to themselves for reforesting their campus. Two small creeks run through the campus site that contribute water to the Rouge River. With the assistance of HarleyEllis, LTU has committed to reforestation practices and innovative stormwater methodologies that are directed at making the campus not only an attractive place to be, but will also make a positive impact on watershed hydrology.

The City of Farmington Hills
Also located within the Rouge watershed, Farmington Hills has spoken in favor of creating a 2.5 mile reforested landscape along a busy road corridor within the city.

Through interaction with the Champion Tree Project International (CTPI), an organization that is committed to the collection, preservation and propagation of the genetics of our remaining virgin old growth trees, both LTU and the City of Farmington Hills are realizing the opportunity to “do more good:” CTPI is providing trees cloned directly from the oldest and largest trees of each species in an effort to reintroduce these old growth genetics back into our nation’s forests and galvanize public support for restoring sustainable community landscapes.

Channelized River Restoration
Work is underway with the Army Corps of Engineers to investigate opportunities for removal of portions of the concrete channel. The renaturalization of the river’s banks will enhance aquatic life habitat and greatly improve the river’s appearance.

The Rouge River National Wet Weather Demonstration Project
Since its inception, the Rouge Project has provided funds and technical assistance to eliminate combined sewer overflows, involve community groups and implement strategies and best management practices to reduce stormwater and other nonpoint source pollution to the river. Water quality has improved within the Gateway Corridor to the point where dissolved oxygen levels are now at least 5 mg. per liter during dry weather. This condition meets or exceeds the State of Michigan’s water quality standards.

Going Forward
Even our “sustainable design” organizations can do ‘more good’.

The US Green Building Council has developed a series of standards called LEEDÆ (Leadership in Energy and Environmental Design). These standards have been developed with a primary focus on buildings and building systems.

While LEED has done some good things to raise the awareness of developers, designers, and politicians to the positive contributions that design can make toward sustainable practices, inadequate attention is given in LEED to the huge opportunity represented by restoration of native plant communities and in particular reforestation, for the benefit of stormwater management and the environment.

Specific credits should be awarded for creating forested areas on-site: not just a few lollipop trees in a sea of asphalt, but densely wooded zones featuring a palette of native trees and ground plane plants. Additionally, credit should be given for maintaining existing trees. Currently, LEED only mentions the use of native species in its discussion of irrigation systems. Tree canopy only is mentioned as it relates to shading pavement. Tree protection is only obliquely mentioned in reference to minimizing the building and construction footprint. Tree protection, tree reforestation and the restoration of native plant communities warrant significantly more attention.

Innovative Techniques
Some excellent techniques are available for the management of the natural systems of vegetation and stormwater. If a greenfield site is the location for development, an inventory of native trees and plants and stormwater movement across the site is a prerequisite to designing with nature rather than against it.

Stormwater management techniques that endeavor to treat the water as close as possible to the spot where it hits the ground create a system that slows the water, allowing for maximum cleansing and infiltration time.

There are many techniques that may be employed in a “treatment train” approach to stormwater management. These include soil decompaction within areas that have incurred heavy equipment or the storage of construction materials, maximizing the length of overland flow of stormwater through bioswales and rain gardens, use of porous pavements, structural soils for use in urban environments that support pavements and trees yet are free draining, planting of deep rooted native plants, replacement of metabolically active minerals, trace elements and microorganism rich compost and, most significantly, maximization of tree canopy through reforestation.

Urban reforestation, coupled with a holistic approach to re-establishing an infiltration based hydrology, can have a tremendous benefit for watersheds and for the quality of life for urban residents. Forested urban environments will significantly reduce runoff, lower stream temperatures, enhance the aquatic environment for plants and animals, reduce energy costs, significantly reduce flooding and the costs of flooding and increase the value of real estate.

About the author: Mark Hieber, ASLA, LEED AP is a landscape architect with HarleyEllis’ (www.harleyellis.com) Detroit, Michigan office. He has participated on the design team for many successful projects throughout the country with specific expertise in developing innovative stormwater management strategies.

Republished from June, 2005 issue of Land Development Today magazine.


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