Land subsidence, sea level rise and urban flooding: coping strategies in coastal cities

Ger de Lange, Tom Bucx, Roelof Stuurman, Gilles Erkens

Chair(s): Esther Stouthamer

Tuesday 30 june 2015

11:00 - 11:20h at Asia (level 0)

Themes: (T) Special session, (ST) Deltas from multiple pressures to integrated solutions

Parallel session: 5C. Special session: Deltas - from multiple pressures to integrated solutions.

Land subsidence increases the threat of urban flooding. This is evident by the increasing instances of coastal flooding in rapidly developing coastal cities, but also the increased runoff from climatic and topographic changes finds its way into subsiding cities. An assessment framework was developed that analyses the situation of a city with respect to awareness, knowledge, data availability, governance and coping strategy concerning land subsidence and flood prevention. We show that cities have seldom reached the stage where a coping strategy is developed, let alone that a governance structure is in place to implement it. This is illustrated by looking at cases, such as Tokyo, Ho Chi Minh City, New Orleans, Jakarta, Dhaka and Rotterdam, where investments in flood risk mitigation run into hundreds of millions of dollars/euros. We show that the timescale of the process leading from awareness to the implementation of coping strategies as compared to the timescale of the development of the flooding threat leads to the conclusion that immediate action is necessary if only to render these investments durable in the long term. We give some examples of the transition from mitigation to adaptation of land subsidence effects.