Low impact development techniques for urban sustainable design: a rain garden case study L. Bortolini and P. Semenzato Department of Land Use and Agricultural and Forestry Systems University of Padova Padova Italy Keywords: rain garden, water retention, low impact development, runoff management Abstract Private gardens and small urban open spaces can play an important role in preventing local floods caused by urban runoff especially during heavy rainfall events. Borders and other garden spaces, designed for the interception, storage and drainage of rainwater, collected by the nearby impervious surfaces, are defined as “rain gardens”. The appropriate planning and design of rain gardens can, at the same time, have a positive influence on the water cycle and offer interesting opportunities for aesthetically creative landscape design. The paper presents a case study of the application of the rain garden model in a public urban site, in the Veneto region. Solutions in regards to dimensioning, species selection, and site preparation are presented. INTRODUCTION In the last decades the high rate of urbanization has resulted in a large increase in impervious coverage in the landscape. Impervious surfaces decrease rainfall infiltration in the soil increasing runoff both in terms of peak flow and volume. Rain water in the urban landscape is therefore mainly directed into the municipal storm sewer system, creating serious problems in case of heavy rains, and reducing water availability and quality. The low impact development (LID) approach has been recommended as an alternative to traditional stormwater design. Such techniques are also called water sensitive urban design (WSUD) in Australia (Lloyd, 2001) and sustainable urban drainage systems (SUDS) in the United Kingdom (CIRIA, 2000). Research on individual LID practices has greatly increased in recent years (Dietz, 2007). There are many solutions available in urban design to reduce stormwater runoff and increase water quality. Many of them are based on bioretention techniques (Prince George’s County, 2007). An interesting approach is to integrate bioretention solutions in the “ornamental landscape” thus adding an other environmental value to the aesthetic component of the urban green infrastructure. In the landscape architecture jargon often such solutions are called rain gardens. Rain gardens are shallow depressions in the landscape that are typically planted with shrubs, perennials, or trees, and sometimes covered with shredded hardwood bark mulch, with a bark mulch layer or a ground cover. They are designed to allow stormwater to infiltrate, recharging aquifers, and reducing peak flows. In addition, they are expected to provide other ecological functions linked to the presence of plants nutrient cycling, air and water pollutant abatement, carbon sequestration, habitat augmentation and connectivity,