GREEN ROOF: RESPONSE TOWARDS EL-NINO AND IMPACT ON RUNOFF WATER QUALITY KHAIRUL RAHMAH AYUB (1) , AMINUDDIN AB. GHANI (2) & NOR AZAZI ZAKARIA (3) (1, 2, 3) River Engineering and Urban Drainage Research Centre (REDAC), Universiti Sains Malaysia, Engineering Campus, Penang, Malaysia redac03@usm.my; redac02@usm.my; redac01@usm.my ABSTRACT Sustainable Urban Drainage Systems (SUDS) promoting numerous type of facilities in stormwater management. The facilities fall in three major group functions namely source control, site control and regional control. Control at source facilities like green roofs, permeable surface and so forth are purposely built to manage rainfall close to where it falls. Benefits of green roof around the globe are very noticeable. This paper will discuss the performance of green roof during El-Nino period and runoff water quality from high intensity rainfall. Intensive green roof is constructed on the top of car parking roof. It was observe daily for one year. Results found that green roof’s contribution in cooling the indoor area of car park in tropical climate region varies during El-Nino period. Its performance relies to the surrounding temperature which during El-Nino, it can increase the surrounding temperature in the range 0.5 o C to 2.0 o C compared to normal period. However, during normal climate, green roof manage to reduce indoor area temperature in the range of 0.2 o C to 2.0 o C. This study shows the green roof manage to perform very well in delaying the outflow during high intensity rainfall. It can retain 100% of rain water or up to 6 months ARI event. However, it depends on the frequency of the events. In term of improving the rain water quality, vegetation used did not gave significance difference in improving runoff water quality. Nonetheless the parameters studied still did not permit according to the National River Water Quality Standard for Malaysia and Malaysia Drinking Water Quality Standard (Raw Water). This study concluded that application of green roof in urban infrastructure like parking areas and bus stops is very promising method for tropical climate countries. Keywords: Intensive green roof; runoff quality; stormwater management; sustainable rrban drainage systems (SUDS); thermal. 1.0 INTRODUCTION Climate changes are providing many challenges around the globe and one of it is El- Nino. During the El- Nino, the weather is possible to be extremely hot and people have to face and deal with the rising temperatures and changes in rainfall patterns are among other effects. People have started to prepare for climate change and are looking for suitable adaptation measures to put in place to manage its impacts. Due to this scenario, the green roof becomes a consideration. Green roofs are vegetated roofs, or roofs with vegetated spaces. The benefits of green roof have been studied widely. It brings a lot of benefits in social, economic and environment aspect. Berndtsson (2010), Getter et al. (2007), VanWoert et al. (2005) and Villareal and Bengtsson (2004; 2005) discovered that it also can create new habitat, filter pollution, decrease noise or noise buffer, improve air quality, reduce microclimate temperature and others as its benefits. Many studies show that green roof can be effective and sustainable facilities in order to reduce the indoor temperature (He et al., 2016; La Roche & Berardi, 2014) and retain rainfall runoff impacts in urban areas (Stovin et al., 2012; 2015; 2017; Grabowiecki et al., 2012; Liaw et al., 2011). The water quality of runoff that comes from the green roof also gain attention of researchers and they found that the performance of green roof varies and relies on many factors like substrates materials, depth, slope, rainfall depth and ect. (Jung et al., 2016; Vijayaraghavan and Raja., 2014; Razzaghmanesh et al., 2014;). In tropical climate weather like Malaysia, receiving high rainfall throughout the year is normal. Availability of big area of tropical rainforest as a water catchment area do not mean that the country is free from the water resources issues. Even though average rainfall per year is 3500mm, the country has problems related to water scarcity and back in 2016, Malaysia faced El-Nino and it worsens the problem. Thus this paper discusses the response of green roof during the El-Nino in reducing the indoor temperature and the runoff quality of rainfall after the El-Nino period. Proceedings of the 37th IAHR World Congress August 13 – 18, 2017, Kuala Lumpur, Malaysia ©2017, IAHR. Used with permission / ISSN 1562-6865 (Online) - ISSN 1063-7710 (Print) 3983