Notes

ZONING
Zoning is way in which the government plans the physical development for the land and its uses. Zoning laws specify the areas where residential, industrial, commercial and recreational take place. Flood prone areas are often zoned with low value developments such as parks and fields for recreational activities. A benefit of zoning is that flood damage is reduced when low-value developments such green spaces like parks and fields are built on flood prone areas. However, challenges are still faced with zoning. Zoning may limit the development of available land because only certain land uses are limited. It is difficult to carry out due to competing land use. The development might also not abide by the recommended land use. An example of zoning is the flood zone of Eagan City in Minnesota, USA. The flood prone areas in Minnesota River are used for low-value developments such as Minnesota Valley National Wildlife refuge and parks. Beyond the zone of low-value developments is the zone of industrial areas. Residential zones are located furthest away from the river so that they houses remain safe from floods.
ELEVATED PROPERTIES
Elevated properties reduce the impact of flooding by elevating properties. Minimum Platform Level(MPL) is imposed on new and existing developments. The MPL is revised when the highest recorded flood changes. A benefit of elevating properties is that the property or development can remain safe from floods up to the MPL. The challenges of elevating properties is that it is difficult to implement as it increases the coast development which will eventually be transferred to its consumers. For example, the government of Singapore set up a MPL of 300mm for areas with no flood history and 600mm for flood prone areas. Existing developments can meet the MPL requirement by building a slope or a series of steps. An example is ION Orchard Mall and Wisma Atria.
LEVEES & FLOODWALLS
Levees and floodwalls are a barrier built higher than the floodplain and river which protect the developments and properties from flood. Levees are raised riverbanks which can be natural(mud) or man-made. Floodwalls are man-made structures, which are made out of concrete. A benefit of building levees and floodwalls is that it is cheaper to raise the height of surrounding land compared to elevating properties. However, the challenges of building levees and floodwalls is that regular maintenance is required to ensure that the levees and floodwalls are strong enough to hold back the floodwater. Levees and floodwater are also unable to prevent flood beyond the level they were designed to. For example, from the 1870s, several kilometers of levees were built along Sacramento River to protect the surrounding land from flood. Another example is that in 2008, floodwalls were built along River Wye
which flowed through Hertford City, UK as part of their defence scheme to protect the city.
CHANNEL IMPROVEMENT
Channel improvement is increasing the capacity of river channels and canals, or to enable water to flow through easily. River channels and canals can be widened and deepened to carry more stormwater away quickly. They can also be straightened to allow water flow through quickly. This prevents water from overflowing. This can be difficult to carry out if the land next to it is used for other purposes. The network of river channels and canals needs to be improved to be effective in migrating flood. A benefit of channel improving is that moderate value development can still take place next to the river channel and canal. However, the challenges of channel improvement is that it may cause problems to areas upstream or downstream of the improved areas, such as the community of plants and animals supported by the river. For example, a section of Bukit Timah canal is widened and deepened to increase channel capacity.