A coupled model for macroscopic behavior of crowd in flood induced evacuation

Floods are regarded as critical disasters that often lead to catastrophic situations and provoke potential injuries and/or fatalities. The consequences of the flood on the exposed population can be realized by exploring the complex behavioral phenomena of the crowd in interaction with the flood hazard. A profound understanding of the time–space distribution of evacuation patterns and vulnerability in floodwater would help in developing a robust risk reduction strategy and mitigating the flood impact. This paper presents a model that combines a macroscopic description of a crowd evacuation model with a hydrodynamic model of flood inundation described by a two-dimensional depth-averaged Shallow Water Equation (SWE), considering two-way dynamic coupling to study the collective behavior of the crowd in a flooded evacuation scenario. Behavioral rules, such as reduced motion in floodwater, route choice through safe areas, and stress due to perception of danger in threatening flood, are imposed to account for the evacuees’ reaction to floodwater. Moreover, the disruption in free flood propagation due to the pedestrians’ presence in the floodplain has also been modeled. The pedestrian model is solved using a third-order Weighted Essentially Non-Oscillatory (WENO3) scheme, and the hydrodynamic model is numerically handled using a high-resolution Godunov type scheme with HLLC Riemann solver. The potential of the developed model is illustrated through two designed hypothetical test cases, which include the crowd evacuation from a supermarket area exposed to a sudden flood.