Fig. 5. The hypothetical dynamic of percent floodable area (PFA). During the process of floodplain urbanization (trajectory A), the city increasingly relies on flood control for flood safety, moving along the upper solid line and shifting dramatically at the threshold T1 (PFA = X1) to the lower solid line. Passing T1, the floodplain has lost the natural functions to handle floodwater, and the city enters the regime where the river is degraded and the socioeconomic dynamics become disrupted and chaotic once a flood occurs. The city could move back to the regime where the river is healthy, and the city can self-organize to remain orderly during flooding by building resilience through increasing percent floodable area and decreasing the reliance on flood control. It is possible to significantly increase percent floodable area by making large and small open spaces multifunctional to convey and store floodwater during wet seasons, and by retrofitting existing buildings to be elevated, floatable, or wet-proofed. During the resilience-building process (trajectory B), the city moves along the lower solid line, but reaching X1 is not sufficient to restore the same degree of resilience before the shift (T1). The city needs to go further, passing T2 (PFA > X2) in order to move back to the more resilient regime.

Fig. 5