Policy Implications of Polder Systems in Jakarta
Our results show that the implementation and management of just 3 polders, namely Kapuk Muara (Kapuk I, II, III), Kapuk Poglar, and Penjaringan Junction (see Tables
21.2 and 21.3), could have a huge impact on reducing overall risk. These could reduce risk by USD 92 million per year under the current situation, or USD 153 million per year under the future scenario (50% of current risk). The three decrease 31% of risk under the future scenario. Total investment of the three is USD 10.25 million, or 3.2% of total cost for all 66 polders.
Our results suggest that building and maintaining the 12 polders shown in Fig. 21.6, to a return period design standard of 50 years (see last column of Tables 21.2, 21.3, 21.4 and 21.5), could reduce the current risk by USD 104 million per year (i.e. 56% of current risk), or by USD 400 million per year under the future scenario (i.e. 81% of future risk). These examples show how risk based benefit-cost analysis can help to identify and prioritize polder construction.