Cover Story
Water-Sensitive Landscaping a Growing Opportunity By Andrea Ludwig, Associate Professor of Ecological Engineering and Extension Specialist, University of Tennessee Department of Biosystems Engineering & Soil Science, Dennis Gregg, Extension Associate, University of Tennessee Extension and Natalie Landry, Project Manager, Knox County Stormwater
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hile in some seasons it is difficult to recall, Tennessee is a wet state, with average annual rainfall from 48 inches to over 70 inches in places, which is well above the national average of 30 inches. These conditions present challenges for landscape managers and developers. Two forces are creating a market for landscaping solutions that address rainwater run-off from developed land, also called “stormwater”. The first is a growing awareness that unmanaged stormwater has damaging impacts on natural resources. To address this, new regulations developed by the Tennessee Department of Environment and Conservation are enforced by local governments seeking to capture pollutants carried by stormwater before they end up in streams and to reduce flooding of streets and lowlying areas. In response to these new rules, proactive municipalities and community groups have encouraged landscaping solutions that use plants and improved soil to soak in water where appropriate, rather than traditional reliance on pipes and concrete drainage channels that contribute to flooding. Rain gardens and vegetated swales are two commonly used landscaping features that add visual interest to a property while providing a valuable function and addressing natural resource needs. Second, growing consumer interest in sustainability is touching all market sectors; from buildings and appliances to the clothes we wear and the food we eat. By definition, something that is sustainable keeps its value and quality while avoiding depletion of resources. It is no surprise then that sustainability is a marketable quality within landscape design and management. In this year’s American Society of Landscape Architects survey of over 850 disciplinary professionals, participants reported a high consumer demand for sustainability. Eight out of the top ten “hot topics” in landscape design currently have a sustainability or conservation element. Rain gardens, reduced lawn area, native plants, and adapted drought-tolerant plants all made the list and each of these are elements of a sustainable developed landscape. The University of Tennessee is partnering with local governments and the Tennessee Nursery and Landscape Association to assist landscapers in helping their clients by creating beautiful, functional home landscapes that integrate water-sensitive landscaping. Educational resources and training are available for
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tennessee greentimes Spring 2019
landscape professionals and will inform how to develop skills in landscape design and installation using natural water features or stormwater flows. This series will focus on how to effectively integrate water-sensitive sustainable landscaping elements (including rain gardens, water gardens (Figure 1), and streamside plantings) into residential and commercial landscaping. The goal is to create landscape features that please the customer and address environmental needs while also meeting regulatory expectations. Rain gardens and water gardens both use rainwater runoff to nurture a specially selected plant palette. Streamside plantings (or buffers) create a natural transition from the water’s edge into the yard or commercial space. Such buffers also provide an important stabilizing function for the streambank itself. Integrating these features into a landscape will lead to new opportunities for plant selection and less maintenance across time. In practice, sustainable landscaping reflects a functional natural environment by creating a resilient and healthy landscape. When planted correctly, plant species that are adapted to local soil and climate conditions will have the best long-term success, so choosing regionally native plants is a basic concept. Plants that can tolerate saturated soils, or short periods of flooding, represent a special subset of native plants and many of these species may be less familiar to many landscapers. See the list of “Plants that Work” for more details. Implementing these best practice approaches may mark a transition from traditional drainage strategies, which were aimed to avoid such saturated soil conditions. The stimulus to make this change, however, stems from our learning that over-reliance on traditional drainage techniques can have undesirable consequences, especially in urbanized areas. Quickly moving an excess of stormwater from the land into streams has three immediate negative impacts. First, any pollutants on the surface end up in the stream and negatively impact stream health; first locally, and then regionally. Second, this rapid increase in runoff water reaching the stream is like discharging a fire hose in the stream channel: these channels erode both down and sideways while trying to contain the new higher volumes, with the subsequent channel damage requiring expensive stabilization efforts to
