With rapid urbanisation in Peninsular Malaysia, almost all rivers passing through populated areas are suffering from water quality degradation. The subject has received much coverage locally the last ten years. This time the primary sources contributing to this pollution are discussed together with necessary containment measures, many of which are in the early stages of implementation. One of the biggest pollutants is sediment from housing development. This can be controlled through the proposed Erosion and Sediment Control Plan (ESCP), required from all such developers before they begin earthworks. Food, oil and grease waste, solid waste from squatter areas, sewage and other major pollutants are also being tackled although progress is slow. Flooding, especially flash floods in urban areas is also another characteristic of tropical rivers subjected to rapidly urbanising catchments. This is being tackled by the new Drainage and Irrigation Department Manual for Urban Stormwater Management ( MSMA) which gives comprehensive guides on drainage control of stormwater runoff from the roofs of individual buildings, through detention and retention measures such as ponds and swales (grass-lined drains). Besides runoff quantity control, there is an urgent need to check the trend in micro-climatic changes in the atmosphere of large urban areas, which is leading to increasing frequencies of extreme rainfall events. This phenomena - "Urban Heat Islands" is given emphasis in this paper to enable greater awareness on the part of technical people involved in urban planning and river management.
