The spatio-temporal effect of a flooding disaster to the economic geography of a city: The case of tropical storm Sendong to Cagayan de Oro City, Philippines

There are growing empirical evidences on the increased frequency and magnitude of flooding disasters caused by climate change. Coastal cities in the global south are confronted with a big challenge in terms of the rising exposure and vulnerability to climate change-induced hazards. In 2011, the Philippines’s deadliest and the world’s second most catastrophic disaster struck Cagayan de Oro City, the study area of this research. Tropical Storm Sendong (Washi) brought city-wide flooding that caused fatalities, population displacement and enormous damages to economic assets. Several areas in the city experienced varying levels of inundation and those areas adjacent to the two rivers suffered deeper, wider and longer submergence. The magnitude of the flood effects was unprecedented prompting urban managers to improve disaster risk reduction and climate change adaptation strategies.

To determine the potential impact of the flooding disaster of TS Sendong, this research calculated the flood impact magnitude index using the Analytical Hierarchy Process. Different parameters of the flood hazard (extent, depth and duration) and exposure (population and business assets) are collected from rich secondary datasets. The computed composite flood index is then subjected to the spatial statistics of ArcGIS to get the hot spot of affected areas in the city. Spatial concentration of business establishments was also generated using similar spatial statistic tool to know the location and distribution of human economic activities particularly the city’s business establishments. Mediation test for the population density changes (as a consequence of the flood) and moderation analysis of the inventory of commercial areas were also conducted apart from determining the causality strength of the flood towards the business establishments. These robust quantitative and spatial statistical tests are performed to derive the relationship of the variables and establish their degree of causality as solid basis for this explanatory case-study research.

The result of the hot spot analysis for the flood impact magnitude index is consistent with the River Basin Flood Modelling simulation and the satellite flood footprint of TS Sendong. However, a key finding of this study revealed that the flood hotspot areas shows similar spatial pattern with the business establishments. The flood affected central business district and its adjacent areas are also the cluster of thriving business locations in the city. One significant finding also revealed that the changes in population concentration due to the fatalities, displacement and relocation do not have significant mediation effects to the resulting number of business establishments in a barangay in the short- and long-run viewpoints. On the contrary, the presence of commercial areas have significant moderation effects to the number and location of business establishments after the flood. Although the flooding disaster has a statistically significant negative effect to the number of business establishments, the spatial clustering trend of the thriving business areas persisted even after the disaster. This research complements the economics of disaster literature by focusing into the smaller unit of the geographic consequences of the flood at the urban level. Further, the findings herein highly suggest as well for urban managers and decision-makers to have a science/research-based disaster adaptation measures to steer development direction away from disaster-prone areas to manage hazard exposure and safeguard lives and economic development.