3. Which parts of the world are most prone to floods? With the help of suitable examples, explain the most common physiographic features that cause flooding of a place.
दुनिया के किन हिस्सों में बाढ़ का सबसे ज्यादा खतरा है? उपयुक्त उदाहरणों की मदद से, उन सबसे सामान्य भौगोलिक विशेषताओं की व्याख्या करें जो किसी स्थान की बाढ़ का कारण बनती हैं।
Demand of the question:
It expects students to give an account of the world’s most flood prone areas. The question also expects an elaboration on the most common physiographic features that cause flooding of a place.
Floods are the most frequent type of natural disaster and occur when an overflow of water submerges land that is usually dry. Floods are often caused by heavy rainfall, rapid snowmelt or a storm surge from a tropical cyclone or tsunami in coastal areas.
The flood prone areas are well scattered in different parts of the country, ranging from the heavy rainfall areas to the scanty rainfall areas. According to the ‘Coastal city Index’, a research based in Netherlands and UK, following parts of the world are prone to flood:
- The South Asia including south eastern part of China.
- African continents South eastern part along with the area surrounding the Gulf of Guinea.
- South eastern part of North American continent and North western as well as South eastern part of South America.
Physiographic causes of flooding:
- Heavy Rains: The simplest explanation for flooding is heavy rains. Heavy rainfall can result in water arriving too quickly to infiltrate the soil. This increases surface run-off, leading water to reach the river channel quicker, resulting in a greater risk of flooding.
- Prolonged rainfall: Soil becomes saturated after prolonged rainfall. This leads to an increase in surface run-off as rainfall can no longer infiltrate the soil. This leads to more water entering the river channel increasing the likelihood of flooding.
- Lack of Vegetation: Vegetation can help slow runoff and prevent flooding. When there is a lack of vegetation, however, there is little to stop water from running off.
- Relief and Melting Snow and ice: The steeper the slope the more rapid the flow of water into a river channel, increasing the risk of flooding. A winter of heavy snow and other precipitation can lead to a spring of flooding. Most mountainous areas experience relatively consistent snowfall totals from year to year, but an unusually heavy winter of precipitation can spell bad news for low-lying areas around the mountains when spring hits.
- Soil type: Very wet, saturated soils, compacted or dry soil can aggravate the flooding in the surrounding area.
- Geology: Impermeable surfaces such as clay and granite do not allow infiltration leading to greater surface run-off. The risk of flooding increases as water reaches the river channel quickly, increasing discharge and the risk of flooding.
Due to global warming as the sea level is going to rise, it is going to increase the frequency of floods in the flood prone areas. Hence, it becomes imperative to be prepared, to tackle the challenge of flooding in near future, as this challenge is going to pose numerous challenges ranging from increasing intensity of flooding to its wide scale effect on the GDP’s of the country.