Jakarta is increasingly threatened by flooding from a combination of land subsidence, rising sea levels (particularly with relation to the spring tide cycle) and higher river levels resulting from increasing rainfall intensity and land use changes within the catchment areas. To respond to such challenges in a manner that is both sustainable and encourages local capacity building, the CTCN is providing technical assistance to Jakarta, to better assess flood risks and hazards, and to design climate-resilient pathways to reduce the magnitude and scale of the impacts from this flooding.
The aim of this technical assistance includes the development of:
• a hydrodynamic flood model that can be used to evaluate a number of hard and soft engineering interventions to reduce the risk of flooding;
• a socio-cultural survey to examine inhabitants’ perceptions of flooding, levels of acceptable risks and preferred adaptation options;
• a series of technology transfer workshops to increase local capacity in high resolution hydrodynamic modelling and use of the model;
• resultant policy and planning recommendations to reduce flood hazards, risk and vulnerability; and
• a roadmap to sustain and expand the project using additional funding streams.
The UNEP-DHI Partnership – Centre on Water and Environment and Jakarta Research Council presents the publication, which describes hydrodynamic modelling for flood reduction and climate resilient infrastructure development pathways in Jakarta. The report's analysis draws the following important conclusions:
- The current flood model setup generates reasonable flood maps consistent with increasing rainfall, tide and subsidence;
- Current flood maps are validated with other models and surveys on 2007 (~50-year return period) and 2013 (~25-year return period) flood events;
- Jakarta flooding is caused more by increased rainfall rather than tide and projected sea level rise;
- Land subsidence significantly worsens the flooding, similar to the findings of previous studies;
- Further analysis of tidal influence shows that coastal flooding from tides is observed only in future land subsidence scenarios (2025 projected ground levels);
- If a worst-case climate change scenario is taken into account, i.e. increased rainfall, the study area is almost fully inundated compared to 2007 flood event;
- The hydrodynamic model also provides the “weak points” where flood starts to overflow. This will help to mitigate the flood with different options.