Lessons learned from applying quantitative vs. semi-quantitative adaptation pathway approach. A case study from Bilbao, Spain

11:15 Thursday 30 May


Room S10


Saioa Zorita (Spain) 1; Maddalen Mendizabal (Spain) 1; José Antonio Martínez (Spain) 1; Efrén Feliu (Spain) 1

1 - Tecnalia

It is more and more recognized that cities need dynamic adaptive plans instead of static robust plans due to climate change uncertainty. Scientific community has found the adaptation pathway as one of the most dynamic available methodologies that can support policy-makers in the formulation and implementation of adaptation measures in a city. The aim of the adaptation pathway, based on threshold analysis, is to contribute to assess and select adaptation options to tackle a climatic hazard or reduce the impacts when considering a specific impact chain.

The adaptation pathway methodology (which is aligned with point 3 & 4 in Urban Adaptation Support Tool) incorporates 3 vital points compared to other methodologies:

  1. Aggregation of adaptation options. This set of adaptation options are called adaptation pathway alternatives
  2. Assessment of effectiveness to overcome the threshold
  3. Sequence the adaptation option over time (pathway design)

This work presents an adaptation pathway developed as a co-creation process (to incorporate the city’s view and objectives) to minimize the risks associated with pluvial flooding in Bilbao. The co-creation activities highlighted that the step-by step methodology may be flexible in its implementation without compromising the final result.

Two pathway approaches are presented and compared for the assessment and selection of adaptation option: a semi-quantitative methodology which uses the existing effectiveness information from literature; and a quantitative methodology which is linked to the use of modelling.

Three of the five proposed adaptation pathways resulted effective in Bilbao. The city considered several criteria for prioritizing the implementation of the adaptation options and for designing the pathway (e.g. cost, maintenance, co-benefits, acceptability by other departments).

This work demonstrated that the semi-quantitative may be a good approach to obtain an adaptation pathway with less resources. The ranking of pathways obtained by this approach followed those obtained with the quantitative approach. This proves the validity of the semi-quantitative approach. Nevertheless, it is important to highlight the benefits that gives the quantitative approach which can be summarized in: a spatial effectiveness of the adaptation options. This allows to zoom in in highest risk areas and see if the proposed adaptation options are enough effective or not (it gives the possibility to benchmark adaptation designs). It also provides the water flow velocity which is directly linked to the impacts of water.