DELHI FLOODS
WHY IN NEWS ?
- Recently, New Delhi’s Yamuna river swelled up and crossed the all-time record level of 207.49m, recorded on September 6, 1978.
MORE ABOUT THE NEWS :
- Around 41,000 people live in low lying areas, which are prone to flooding, around the Yamuna in Delhi.
- Around 8000-9000 people have been evacuated so far. The monastery area and the boat club in the central district are vulnerable points.
REASONS FOR SUCH HEAVY FLOODS IN YAMUNA :
Water released from Hathni Kund barrage:
- 3,59,000 cusecs of water was released from the Hathni Kund barrage into the Yamuna.
- The water from the barrage takes up to 72 hours to reach Delhi and a warning has been issued as the water levels are further likely to rise.
Heavy rainfall across north India:
- As per officials, the sharp rise in the water level of the Yamuna river is possibly a result of incessant and heavy rainfall in upper catchment areas including Uttarakhand and Himachal Pradesh.
- Also, the soil is likely saturated due to heavy downpour in Delhi as well as neighbouring areas.
- The heavy rainfall across several nearby states and upper catchment areas has led to a rise in the water levels of several rivers, creeks and drains.
- Delhi central is more responsive to rainfall induced surface runoff and soil erosion due to its high relief and landscape configuration.
- Change in land use pattern in last 30 years significantly increases the area of impervious surface and eventually decreases the infiltration rate in Delhi region.
- The expansion of built-up area at the expense of vegetation cover, agricultural land and open spaces eventually affected the hydrological ecosystem of the Delhi region.
- Lower infiltration rate in Delhi east and Delhi central catchments increases direct runoff and pose serious threat of flooding during a prolonged rainfall.
ABOUT YAMUNA’S CATCHMENT IN DELHI:
- Yamuna river forms major sub-basin of the Ganga river system that covers 42.5% of the total catchment area of Ganga basin.
- Yamuna is the main river system of Delhi region and major perennial source of water.
- Delhi region, the National Capital Territory of Delhi is situated in the southwest part of Gangetic plains and covers an area of 1483 sq km with maximum length of 51.90 km and width of 48.48 km respectively.
- The average annual rainfall is 714 mm, 3/4th of which falls in the monsoon months of July, August and September.
- Due to increase in water level in Yamuna river during heavy monsoon rains, Delhi region experiences flood situations during extreme events.
- It has been affected by many severe floods in the past.
- Rainfall trend for past 30 years (1989 to 2017) has been analyzed and observed that Delhi received maximum (about 83%) rainfall during monsoon period from July to September.
- During this period, Yamuna river flows with maximum water level causing flood conditions in low lying areas of Delhi central and Delhi east sub-basins.
- Most severe was the September 1978 during which the water level of Yamuna river crossed its danger mark (204.83 m).
SYLLABUS: PRELIMS, CURRENT AFFAIRS
