Sponge cities

Context: The idea of sponge cities idea needs traction at a time when discussion on urban flooding is reduced to simple contradictions.

Mention the causes of flooding in Hyderabad.

• Non utilization of tools: Climate change adaptation tools for Hyderabad built by the Potsdam Institute for Climate Impact Research, Germany was not used.
• Excessive rainfall: In September 2019, the rainfall was the highest in 100 years, while in October it was in 62% in excess.
• Inability to manage the city’s drainage systems: The floods of October 2020 occurred because the water was not discharged in time and when it was discharged, it was done suddenly, in an uncontrolled manner.
• Outdated infrastructure: Hyderabad’s century-old drainage system (developed in the 1920s) covered only a small part of the core city. The city has grown at least four times its original built-up area in 20 years, into areas where there was no drainage infrastructure.
  • The risk is going to increase every year with changing rainfall patterns and a problem of urban terrain which is incapable of absorbing, holding and discharging water.
• Communities are left out: The issues of incremental land use change; particularly of those commons which provide us with necessary ecological support, such as, wetlands are neglected.
  • This framing also rejects the role of local communities in managing local ecosystems; people with traditional rights for fishing and farming.

How the idea of sponge cities can help us tackle the issue?

• A mission that mitigates flood risk and provides a pathway to water security is required. The most promising idea across the world at this time appears to be the idea of “sponge cities”.
• The idea of a sponge city is to make cities more permeable so as to hold and use the water which falls upon it.
• Sponge cities absorb the rain water, which is then naturally filtered by the soil and allowed to reach urban aquifers.
  • This allows for the extraction of water from the ground through urban or peri-urban wells.
  • This water can be treated easily and used for city water supply.
• In built form, this building attached open green spaces, interconnected waterways, and channels and ponds across neigh bourhoods can naturally detain and filter water.
• These can all be delivered effectively through an urban mission along with the Atal Mission for Rejuvenation and Urban Transformation (AMRUT), National Heritage City Development and Augmentation Yojana (HRIDAY) and Smart Cities Mission.
• Regardless of ownership, land use on even small scale wetlands needs to be regulated by development control.

Suggest some governance reforms to deal with urban flooding.

• Watershed management and emergency drainage plan should be clearly spoken in policy and law.
• Detailed documentation of urban waters must be held by agencies which are not bound by municipal authorities.
• Natural boundaries such as watersheds instead of governance boundaries like electoral wards for shaping a drainage plan should be considered.
• The Metropolitan Development Authorities, National Disaster Management Authority, State revenue and irrigation departments along with municipal corporations should be involved in such work together.
• Ban against terrain alteration: Terrain alteration needs to be strictly regulated and a ban on any further alteration of terrain needs to be introduced.
• Cities are becoming increasingly impervious to water because of the nature of materials used (hard, non-porous construction material that makes the soil impervious).
• New porous materials and technologies must be encouraged or mandated across scales.
• Examples of these technologies are bioswales and retention systems, permeable material for roads and pavement, drainage systems which allow storm water to trickle into the ground, green roofs and harvesting systems in buildings.

Way forward

• Acknowledging the role of different actors for the city can create a practical space to begin this work.
• We need to urgently rebuild our cities such that they have the sponginess to absorb and release water without causing so much damage to the most vulnerable.