Green is good: establishing a green infrastructure can help protect an area's natural waterways - Column

A linked system of trails, green ways, parks and other open space areas makes any community a better place to live. Waterways in an area can become the foundation of a green infrastructure in a community. Waterways provide enormous benefits to a community in addition to their recreation potential. Waterways can provide fish and wildlife habitats, economic benefits and perform ecological functions.

These environmental features foster greater value for a region. A well-planned system of open space helps to attract new businesses and reduce pollution. Traditional maintenance costs are reduced because protected green areas don't require the same high level of maintenance as many traditional parks. By protecting our riparian corridors, traditional infrastructure cost is reduced, because there's less damage to that infrastructure from degradation of a waterway.

Ecological restoration of park waterways and surrounding lands is most beneficial for a region when accomplished in several ways: through a holistic approach to watershed management that extends beyond municipal boundaries; by using bio-stabilization with natural materials to repair damage; and by establishing preventive measures for development, improving the community at large. Let's look at each of these topics.

Holistic Approach

Municipal storm water management has undergone many changes in the last decade. Historically, rapid urbanization of many small watersheds has led to vast changes in the way water is channeled. Streams respond to land-use changes by incision of the channel bottom, which causes the banks to be undercut, uprooting vegetation. Stream banks begin falling into the channel, and sediment problems develop, seriously polluting the water. Property losses occur as the channel form changes and directly impacts parks, residences, businesses and municipalities.

In an effort to solve these stream problems, "hard" engineering solutions such as piping, digging new channels, lining channels with concrete and other methods have been the traditional approach. Evidence shows that a hard fix in one location often leads to a problem in another location. Hard fixes frequently are prone to failure as the channel continues to change. In addition, hard engineering solutions will eliminate the important aesthetic and critical biological functions of a stream.

Alternative methods of storm water management include a non-structural, holistic approach that reduces the problems of traditional approaches. A community or region needs to take a comprehensive look at its waterways. Ideally, this will happen before an area is developed. However, a non-structural, holistic approach has application on a watershed that has already urbanized.

Ecological restoration of a waterway should be based on its geographic boundaries or divisions, rather than on various municipal boundaries. Addressing or attempting to solve storm water-management issues based on political subdivisions forces the problem and shifts costs to another entity. Communities in a region need to unite to address the issues related to wetlands, streams and rivers, and decide how to protect those areas. Together, the group can identify waterways within the municipalities that can become a vital link in an open space system. A holistic approach looks at the land use changes occurring in a water-shed and manages those changes in an ecologically sensitive manner.

A holistic approach also means that waterways need to be examined at both the macro-level and micro-level. At a macro-level, protecting flood-plains and ecologically sensitive areas as part of a big river system has immense benefits to a community and region, as does protecting riparian corridors of a smaller stream. On a micro-level, on-site storm water, erosion and sediment control directly benefit our creeks and streams. By looking at the big picture instead of just runoff control or flood control, other benefits of a holistic approach to storm water management become apparent. In addition to riparian features, communities should review bluff lines, steep slopes and other areas that may need protecting. By protecting our creeks, streams and rivers and related features such as wetlands and other ecologically sensitive areas, an attractive, sustainable green infrastructure can be established that's highly beneficial to the region as a whole.

Benefits of Biostabilization

Biostabilizing stream banks, introducing best-management practices, protecting existing river corridors and establishing new corridors are all methods that can be used in place of or in conjunction with traditional engineering solutions to address problems occurring in watersheds that have been impacted by urbanization.

A water channel is in a constant state of change. The rate of change varies greatly with the conditions of the watershed. Hundreds of years ago, the rate of change in stream channels was relatively slow, caused only by minor erosion of stream banks. Stream systems established a dynamic equilibrium that functioned within a limited range of natural events, flow and sediment loads. A major storm or flood event periodically would upset the balance, but the channel would adjust rapidly and again reach equilibrium.

With increasing development and urbanization, the rate of change in water channels has increased drastically. Shallow channels have become deeply incised, cutting new channels through the headwater areas where none previously existed. In a non-urban, forested setting, most precipitation is absorbed where it falls, and is slowly released into the stream channel. In an urban setting, however, most precipitation isn't absorbed, and flooding results from the excess storm water that has no place to go.

Storm-water management techniques used to consist of intercepting storm water runoff by a curb and gutter, and directing it to an inlet. Once the runoff entered the inlet, it flowed underground inside a pipe until discharged into a channel. The absorption potential of the watershed was eliminated, and the system's ability to slow the flow of water was reduced. The ultimate result was that the overall volume of water entering a channel was increased, and the time it took to reach the channel was greatly decreased. The impact on channels has been damaging, making them prone to frequent flash flooding.

Ecological restoration of the natural functions of waterways can be achieved in a non-structural, green way by identifying areas that need to be protected or restored, and determining how to create the most natural habitat. Biostabilization and other non-structural measures can be used to reduce the volume and rate of runoff, and stabilize channels to prevent or slow the rate of further degradation, ultimately leading to property damage.

Within existing parks, wetland, wet meadow, prairie and forest areas can be re-established. Creeks, for example, can be revived by daylighting or removing the existing storm-sewer pipe, an approach that's most effective for small channels in headwater areas. Head cutting can be stabilized to create all attractive riparian corridor.

To reduce the amount of storm water flow in a park setting, curbs can be eliminated from parking lots and the amount of hard surface parking reduced. Water can be directed into small detention areas and allowed to infiltrate into the ground, maintaining the variable source flow of the natural system. Open channels or gravel and rock-filled drainage structures can be used to collect water and allow it to infiltrate. Minimizing the amount of grading will reduce compaction of soil, increasing its infiltration capability.

In a natural system, storm water enters a stream at multiple points, as opposed to using engineering methods that discharge water in high volumes from a few points at a high rate of speed. By using, this non-structural method, channel damage is reduced and the ecology of the riparian corridor area is protected.

Other non-structural methods can be used to improve the stream channel. Preserving and maintaining the meanders that occur in a stream will slow the rate of flow particularly for smaller storm events. Protecting the riverbed vegetation and wetland areas adjacent to the stream will trap the sediment, slow the rate of overland flow and protect the channel top of the bank. Large root wads can be anchored to the bank to trap sediment, absorb energy and deflect the flow of water. Erosion-control fabrics and mats made of biodegradable materials can be used to stabilize slopes. Layering wrapped earth and combining this with branch packing can stabilize slopes and channel banks. Off line detention areas, which function similar to a flood plain or wetland storage of floodwater, can be created adjacent to channels to reduce peak flows.

Community Benefits

Using these and other non-structural storm water management techniques will have multiple community benefits. One of the most significant will be improved water quality. Reducing the amount and rate of runoff will reduce erosion and sediment in the water. Changes in land use surrounding waterways allow them to become part of a greenway system of linked parks and trails for a community, providing a multitude of social, economic, cultural and environmental benefits.

As communities work together to look holistically at waterways and associated land, development guidelines can be established that will prevent further damage and protect property values. Local developers should be encouraged to protect these areas. In return, developers can be allowed to build at a higher density for the same economic investment in places that will not damage waterways.

Establishing a green infrastructure that protects and nurtures the natural ecology of waterways enhances an entire region's ultimate livability for many years to come, and restores its value.

John Hicks, AICP, ASLA, is a group manager for Woolpert LLP's Landscape Architecture and Planning group in St. Louis, Mo. Throughout his career, he has been involved in a wide range of environmental, planning and site-development projects. He has also worked on watershed management, wetland restoration, prairie restoration, mined land reclamation and coastal-zone management projects.

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