The urbanization process has changed the land use pattern and urban structure. Urban development adds impervious surfaces, increases runoff, decreases infiltration, groundwater recharge and has negative effects on the local water quality and quantity balance. A large portion of former forest and agricultural areas have been cleared and replaced by concrete buildings, roads and drainage systems which are impermeable. The rivers flowing along the urban area are choked up with sediment from mining, housing and other development areas. The problem of silting in rivers and drains together with high rainfall intensity causes flash floods. The phenomenon of these flash floods has become more common as the surface runoff from developed urban and industrial areas has fully increased the peak discharges entering the rivers with a shortened time of detention to peak flow. This book is intended to give the understanding of the fundamental and design criteria of constructed wetland based on various guidelines from local and oversea. The performance of constructed wetland for tropical climate based on Malaysia condition has been discussed as well in this book. This book consists of four cha