Grounded Resilience

Abstract

As populations continue to grow, cities also continue to densify and expand. In this process, natural surfaces are increasingly replaced by impervious surfaces, which reduce the ability of rainwater to infiltrate into the ground. This increases pluvial flood risk and shows the need to rethink how urban areas are built. One way to do this is by making room for more natural areas within the urban fabric. However, in dense cities where space is limited, these areas also need to perform multiple functions. Blue-Green Infrastructure offers this form of spatial adaptation by combining rainwater regulation with other urban benefits. While some BGI strategies are applied at the building scale, this research focuses on ground-based BGI adaptation: strategies applied to open spaces and ground surfaces at the urban scale.

Ground-based BGI adaptation is often evaluated through its ability to reduce flood hazard in general. However, when adaptation resources and available urban space are limited, it becomes important to ask where adaptation can create the most meaningful improvement. This is why a more targeted receptor-based perspective matters. Among the many urban receptors affected by flooding, this research focuses on buildings and examines how building flood-resilience improvement can be understood through an urban adaptation lens. Reflecting the idea of Grounded Resilience, the research explores how building-level flood-resilience assessment can be used to ground the spatial design of ground-based BGI adaptation strategies. To do this, the research develops a Grasshopper-based rainwater simulation workflow that links BGI adaptation with building-level flood-resilience assessment. The workflow connects particle-based runoff simulation, BGI absorption logic, flood-depth estimation, and building-level resilience scoring within one design environment.

The workflow is tested in the Lijnbaan area in Rotterdam using terrain data, 3D building geometry, building attributes, rainfall input, and selected BGI scenarios. The results show that BGI effectiveness is not determined by storage capacity or adapted area alone, but also by its position in relation to runoff pathways, accumulation areas, and affected buildings. Therefore, BGI adaptation should not only be evaluated through general flood-depth reduction, but also through its ability to reduce flood impact where building resilience is most affected. The workflow enables scenario comparison through absorbed volume, flood-depth changes, resilience-score differences, movement-path visualisation, and indicative implementation cost.

The research shows that the developed workflow is most useful as an early-stage comparative design-support framework, rather than as a fully calibrated hydraulic or damage-prediction model. Its value lies in connecting site runoff behaviour with building resilience outcomes, helping designers identify where BGI adaptation may create meaningful local improvement and where adaptation is most needed.