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Hyderabad Urban Floods: Reasons and way forward

• What are urban Floods?
• What are the reasons of Hyderabad Urban Floods?
• Other common reasons for Urban flooding
• Impacts of urban floods on vulnerable section
• Steps taken to tackle Urban Flooding in India
• Way forward

Introduction

The phenomenon of urban flooding in India is not new, every year at least one major city of India faces this disaster. Urban Floods in Chennai, Mumbai and Kerala in the last few years are few of those examples. At present, Hyderabad is suffering from this phenomenon.

What are urban Floods?

• Ideally, Flood is defined as an overflow of a large body of water over areas not usually inundated. This definition doesn’t fit well in the cases of Indian cities. flooding in urban areas is not only due to overflowing rivers, unplanned and underdeveloped mand-made structures also play a large role.
• Hyderabad as the city has experienced floods earlier in 2000, 2008, 2016 and 2017 as well and led to at least 2 dozen casualties every time.
• Musi river which was struggling to flow till last month is overflowing and breaching the banks.
• Present Hyderabad flood has claimed more than 30 lives in Telangana since October. The reason behind casualties are wall collapses, electrocution and people getting washed away in overflowing nalas.
• National Disaster Response Force (NDRF) and Army have been deployed for rescue work.

What are the reasons of Hyderabad Urban Floods?

• A deep depression in the Bay of Bengal that moved towards Telangana. It led to the highest rainfall for October recorded in Telangana’s capital since 1903. the monthly average rainfall of Hyderabad for October (103.6 mm according to Skymet) was surpassed on a single day when 192 mm of rain fell.
  • Musi river, which was turned into a Nala, started to overflow due to heavy rain.
• Hyderabad is in between the system of catchments: The western edge is in the Godavari River basin, To the east, it’s in the Krishna River basin and Hussain Sagar Lake in the middle of the city. Musi river(overflowing) is going through the city connecting waters of several lakes.
• Moreover, due to the topography of Deccan Drainage pattern is chaotic i.e. it doesn’t flow in any single direction.
• Encroachment of storm-water drains: Several buildings and houses have been built without taking into account the floodwater Nala there, effectively closing the space for the exit of water from the city.
• Encroachment on water channels: This situation has occurred due to those hundreds of lakes which were connected by water channels in the past & those, which typically lie in the valley areas now encroach upon by the buildings.
• Waste management– Every water body has a holding capacity. But, with all the industrial waste and sewage being dumping into the lakes, the waste accumulated and has now affected the holding capacity of the lakes.

Other common reasons for Urban flooding

Hydrological Factors: Overbank flow channel networks, the occurrence of high tides impeding the drainage in coastal cities.

Improper waste management system: Clogging of storm-water drains because of silting, accumulation of non-biodegradable wastes and construction debris.

Anthropogenic factors

• With the rapid urban expansion, corruption and administration neglect has allowed construction on increasingly reclaimed wetlands, flood plains and low lands of the city as these areas have a cheaper land rate.
• One such example is Chennai International Airport, which was built over the Adyar river. The airport is located on riverine floodplains leading to the 2015 flooding of Chennai.
• Andhra Pradesh’s Amaravati had major projects proposed for building over the floodplains of Krishna river.
• In the 2000s, Akshardham Temple Complex and Commonwealth Games Village (CWG) was built without taking Yamuna floodplains into consideration. The village was built right on the Yamuna’s floodplain.

Impacts of urban floods on vulnerable section

• The communities of people that are the most vulnerable to these disasters are those living in squatter settlements, slums, pavement dwellers, living in suburban and low-lying areas that remain waterlogged many days after flooding also. People end up living without services, shelter, potable water, food.
• These floodwaters with untreated solid waste and faecal matter flow around these squatter settlements and become responsible for outbreaks of diseases such as malaria, dengue, diarrhoea etc.
• Lack of discernment in development adds to this vulnerability of the poor. During the 2015 Chennai floods, some of the worst impacted areas were slum resettlement tenements constructed by the government on floodplains or lake catchment areas at Semmencheri, Perumbakkam and Ezhilnagar.

Steps taken to tackle Urban Flooding in India

IFLOWS-Mumbai: It is an Integrated Flood Warning system to enhance the resilience of Mumbai by providing early warning for flooding especially during high rainfall events and cyclones.

The system also has provisions to capture the urban drainage within the city and predict the areas of flooding.

CFLOWS-Chennai: CFLOWS is a complete web GIS-based decision support system that can be used both for mitigation planning operations before flooding and in real time to for aspects like relief work.

It is an integrated system that involves coupling models of regional weather forecasts, storm surges and captures about 796 flood scenarios.

Flood forecasting initiative: It aims to provide alerts to the public regarding flood situations in the region. It also offers current water level in the flood affected regions in the country and colour-coded maps indicating flooded areas.

READ – NDMA guidelines on Urban Flooding

Way forward

• As the incidence of climate variability and extreme weather events increases, and urban flooding becomes more and more common, we must focus on the factors that can be controlled.
• Water sensitive urban design and planning techniques — especially in the context of implementation — are of utmost importance.
• These methods take into consideration the topography, types of surfaces (pervious or impervious), natural drainage and leave very less impact on the environment.
• our proposed infrastructure (especially stormwater drainage) has to be built considering the new ‘normals’ (increasing rainfall or cyclones). Tools such as predictive precipitation modelling can help do that.
• Most important is strong land use controls. EIAs and enforcement will remain vital to ensure that fragile wetlands and floodplains are not concretised.
• Minimize the surface runoff- Limit, reduce or mitigate for impervious surface throughout the watershed by use of new engineering techniques like pervious pathways, parking lots should be considered and implements wherever possible to minimize the surface runoff.

Read more:  

Hyderabad urban flooding

Flood management in India – an overview