Barriers can be employed in conjunction with excavated pools, constructed across a drainage way or off-stream and connected to the stream by a flow diversion channel to trap and store waterborne sediment and debris. A natural or man-made topographical depression that causes the line-of-sight to a sound source can be just as effective for noise control as a barrier. Individual license of libraries used is found in license file in the source. Vancouver is limiting the amount of water going into the stormwater system by collecting it at the site of individual homes and businesses through the reintroduction of rainbarrels or underground storage. Best practices for managing stormwater There are many ways of managing stormwater, including regional landuse planning and conservation of wetlands, aquatic buffers, stream corridor management (including erosion and sediment control), better site planning, and on-site storm water treatment practices that improve water quality (Fig. 6). Some of these are large-scale efforts, and others very specific on-site design and management ideas. Similarly, a flood that has a ten percent chance of occurring in any given year is terms a “ten-year flood.” Urban development increases the peak discharge rate associated with a given design storm, because impervious surfaces generate greater runoff volumes and drainage systems deliver it more rapidly to a stream (Fig. 5). Fig. 5. Predevelopment and postdevelopment f loodplain elevations. For example, a flood that has a fifty percent chance of occurring in any given year is termed a “two year” flood.