Abstract:
Transport systems are vital to the functioning of urban areas. Minimizing disruptions to
transport networks due to natural hazards is a key goal in disaster-resilient urban planning.
This study presents a framework to assess transport networks’ resilience to urban flooding.
The proposed framework is developed based on network centrality and graph theory. The
study utilizes betweenness and closeness centrality to capture transport network resilience
under two movement thresholds: pedestrian movements (r=1km) and vehicular movements
(r=10km). The study utilizes Open Source GIS tools to compute centrality values. The case
study is carried out in Greater Colombo, Sri Lanka and selects three significant urban
flooding events, i.e. 2010 May 17, 2016 May 15 and 2017 May 25. It assesses the
transportation network resilience in two respects. First, the topological impacts from each
flood event to the transportation network. Second, the accessibility changes in the
transportation system. The results reveal three key findings. First, compared with direct
impacts on the transportation network (≤7%), the relative impact is significantly higher
(>60%). This is particularly pronounced in vehicular movements relative to pedestrian
movements, because pedestrian movement is hindered by floods where there is a loss of
several road segments in a given neighbourhood. For vehicle movement, floods significantly
impact the entire transportation system and their pass-by trips. Second, the study revealed
redundant depreciation of the transportation accessibility as it shifts the accessibility from
downtown (CBD) to suburban areas and creates temporary accessibility hotpots in certain
local areas. Third, considering the statistical distribution of network centrality, the study
identifies significant declines of transportation accessibility in each flooding event,
significantly impacting trips of longer length (>10km) as the loss of shortest path roads
segments significantly impact the pass-by movements of the transportation system. The
proposed framework can be utilized as a planning tool to assess transport network resilience
and devise precautionary measures to mitigate disaster risk.
Citation:
Kalpana, L.D.C.H.N., Jayasinghe, A.B., & Abenayake, C.C. (2020). Network centrality assessment (NCA): assessing the transport networks’ resilience for urban flooding [Abstract]. In T.L. Gunaruwan (Ed.), Proceedings of 5th International Conference on Research for Transport and Logistics Industry 2020 (p. 4). Sri Lanka Society of Transport and Logistics. https://slstl.lk/r4tli-2020/