Topics Covered: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc., geographical features and their location- changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.
Why floods occur in Hyderabad?
Context:
Hyderabad was recently listed as the rainiest place in the country by Skymet, an independent weather forecasting agency, on Sunday after it recorded 72.5mm of rainfall.
- The city has witnessed its third wettest day of October in the last 10 years- As per India Meteorological Department (IMD) data, Hyderabad witnessed 98.3mm rainfall on October 10, 2013 and 82.6mm on October 3, 2017.
Rainfall this month:
The IMD data indicates that the city has been pounded with 356mm of rains in 18 days, which is four times higher than the normal rains.
What caused this havoc?
This was caused by a weather that formed in the Bay of Bengal, hit the east coast and moved westward, weakening on the way.
- Normally, cyclones lose steam upon making their landfall. This particular system, however, clocked a long east-west track cutting across Andhra Pradesh, Telangana, north-interior Karnataka and Maharashtra.
- All these states experienced above-normal rain during the recent monsoon season. As a result, the soil in these regions has retained significant moisture content.
- In addition, vertical wind shear — the result of a significant difference in wind speed between higher and lower atmospheric levels — helped the system maintain its intensity as a deep depression or a well-marked low pressure area even on land.
But, why floods occur in Hyderabad?
Hyderabad is a system of catchments.
- The western edge is in the Godavari river basin.
- To the east, it’s in the Krishna River basin.
- Also, Hyderabad is in the Deccan region, which has a chaotic drainage pattern — water here does not flow in a single direction as the slope is in multiple directions.
What efforts were made in the past to control floods?
In 1908, devastation caused by a cloud burst and the flooding claimed 15,000 lives and rendered 80,000 homeless.
Sir Visvesvaraya was commissioned to conduct a study and suggest measures to manage the impact of floods on the city. Following this:
- Two reservoirs — Osmansagar and Himayatsagar — came up.
- A modern system of drainage was also built.
What has not been addressed?
- The city has been built on top of the agrarian imprint. Sensitive catchment areas have been illegally occupied.
- Roads have been built, which are rigid boundaries, around the ‘fluid’ water bodies, without any buffer areas.
- Unchecked real estate growth.
What needs to be done now?
- Take stock of the entire drainage system, not just the nalas.
- See the whole city as a catchment area and begin to clear critical areas of encroachments.
- For all this to be implemented, we need an executive and ‘ecological’ body like a “Lakes and Parks Authority”, can draw upon and coordinate the relevant parts of the functions at Hyderabad Metropolitan Development Authority (HMDA), Greater Hyderabad Municipal Corporation (GHMC) and departments like revenue, irrigation, roads and buildings.
- Risk mapping of the areas of the city should be done to assess the vulnerability, related to urban floods, using GIS technology.
- Town Planning department of GHMC should regularly monitor the prohibited areas to prevent encroachments.
- Conserve and protect areas for groundwater recharge.
InstaLinks:
Prelims Link:
- Godavari river basin.
- Krishna river basin.
- What are cyclones?
- Temperatures in eye of a cyclone vs other regions.
- Cyclones vs Hurricanes.
Mains Link:
Discuss the causes of recent floods in Hyderabad. What measures should be put in place to manage these floods?
Sources: Indian Express.
