Effects of Ubanization on Flood Control

flood controlUrbanization is good. Paved roads, tall buildings, better industrial, commercial and even residential real estates. Urban planners project growth when areas are urbanized and developed. All is well since most often than not, cities grow, businesses flourish, people generally become happy.

But there’s one thing that urban planners despite their experience fail to anticipate (or do they just ignore it?), drainage systems. It can be a small thing but when water runoffs begin to surge in, a huge disaster can easily happen when such a small thing is left unchecked.

Local building codes, national regulation and building policies dictate that urban planners should take into account a kind of sustainable management of surface water into their urban drainage system plans. So many cities, towns and communities in the US have had to deal with floods due to urbanization.

Changing land use is seen as one of the culprit. By constructing roads, buildings and houses on lands that once contain a variety of vegetation increases the amount of runoff waters to streams during rainfalls or snowmelts. Not to mention the artery of drainage systems beneath the urban cities all lead excess water to nearby streams. With the excess runoff going into only a few streams, overflowing is inevitable and flooding is only a matter of time.

Moreover, land use development sometimes changes stream channels in favor of bigger buildings and wider paved roads. This move can definitely limit the stream’s capacity to hold flood waters or runoffs. Furthermore, if urban developers perform constructions in already flood prone areas, the already high flood risk area would only increase affecting as well the newly constructed buildings and or any improvements that have been introduced in the area.

With an already limited storage capacity, streams will not be able to handle the volume of water coming from rainfall and snowmelt. However, aside from land use other factors that affect stream channel changes and water volume capacity include geology, topography, basin size and shape, and storm patterns. It has been observed that urbanization has a greater effect over small stream basins than bigger ones.

Smaller basins are more likely to loose most of its original vegetation and will likely have drastic changes in their network of water channels compared to bigger basins. This susceptibility of smaller basins makes it even more a important that urban engineers carefully take into account their existence and incorporate them in their planning.

Urban planners should gather complete and accurate information regarding stream flow and determine how the present land use affects the flow of the water in and around the area. This way they can help find solutions to reduce current or future flooding in the areas.

The full effects of urban development can be felt during moderate storms that follow periods of dry spells. The run offs from the rainfall could turn regular runoffs into flash floods.

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