Water Resources Engineering (WRE) connects engineering hydrology and hydraulics with global, economic, environmental, and societal issues. Our student Andrew LaPolt makes this connection here…

The article “Deforestation in Snowy Regions Causes More Floods,” was published by Science Daily on October 3, 2012. This water resource engineering issue relates to the hydrology domain of water resources, specifically the occurrence of flooding. In the interior regions of North America, many creeks and rivers get most of their flow from melting snow accumulated during winter storms in mountainous areas (Science Daily, 2012). How much water flows down these streams is dependent on how much snow falls upstream and how fast is melts. Usually trees control the snowmelt by shielding the snow from sunlight. However, deforestation in these regions can cause the number of floods in the area to at least double if not quadruple (Science Daily, 2012). The common perception in hydrology is that deforestation in these areas makes seasonal floods bigger, but has little impact on the number of large floods over time. In the past, chronological pairing was used to describe how floods become larger in deforested areas. But, a new study uses frequency pairing to determine how often a flood of a certain size with return. This study suggests that deforestation consistently causes more floods– both big and small (Science Daily, 2012). This story makes sense because the lack of trees in a mountainous area would cause the snow to melt much faster and increase the amount of runoff that occurs. In a paper written by Kuchment, describes how vegetation can lead to sublimation or redistribution of snow by trees and that 30-35 per cent of snowfall is intercepted by conifer stands and 7-10 percent by hardwood stands (Kuchment, 2004). He also talks about how deforestation reduces infiltration and improves conditions for overland flow, causing flood runoff and peak discharges to increase (Kuchment, 2004). A paper by Alila talks about how chronological pairing is more focused on flood magnitude and not frequency like frequency pairing (Alila, 2009). This paper also talks about how chronological pairing should not be used to predict the impacts of forest harvesting on large floods (Alila, 2009). This article left out a comparison of values between the amount of runoff in a forested versus a deforested area which would have given a better reference of the magnitude.

This article also relates to the broader context of the environment and the impacts deforestation and increasing frequency of floods have on it. The increasing frequency of runoff and floods has a major impact on both the terrestrial and aquatic ecosystems in that area. Some of these impacts can be increased erosion, loss of habitats, increased sediments and many others. The paper by Kuchment also relates to the environmental aspect of this issue. He talks about how in many regions deforestation has led to a significant increase in disastrous floods and has also caused severe soil erosion (Kuchment, 2004). In closing, this was an important news story because it shows the impact that humans have on the environment and how we can alter the hydrologic cycle in certain areas. 

Trees in snowy, mountainous areas, such as these near Cotton Creek in the Columbia Mountains, help keep floods under control. A new study shows that deforestation makes large floods more frequent. (Credit: Kimberly Green)

 

Sources:

Alila, Y. (2009). Forests and floods: A new paradigm sheds light on age-old controversies. Water Resources Research, Vol 45.

Kuchment, L. S. (2004). The Hydrologic Cylce and Human Impact On It. Moscow, Russia: Water Problems Institute, Russian Academy of Sciences.

Science Daily. (2012, October 13). Deforestation in Snowy Regions Causes More Floods. Retrieved from Science Daily: http://www.sciencedaily.com/releases/2012/10/121003132334.htm

 

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