*2.1. Construction of a Resilience Assessment Framework for NBS*

A new methodology for the construction of a specific assessment framework to evaluate the NBS contribution to urban resilience, with focus on solutions for stormwater management and control, is presented. The specific NBS considered in the RAF are the following: infiltration basins, green roofs and walls, vegetated swales, infiltration trenches, and porous pavements. This methodology allows to develop a multidimensional and comprehensive RAF that considers a broader definition of urban resilience. The methodology considers objective and subjective information and allows resilience to be measured on a single scale. As previously mentioned, urban resilience is defined as a city's ability to absorb disturbances, learn from the past, adapt, transform and prepare for the future. In this

sense, the RAF considers five *capabilities* of a resilient city—namely, absorb, learn, adapt, transform, and prepare.

The proposed methodology is based on the performance assessment structure proposed by the ISO 24500 standards [34–36] for water supply and wastewater system management. The ISO 24500 structure is grounded on the definition of objectives, criteria and metrics. In the proposed methodology, resilience objectives aim to consider the several NBS contributions to urban resilience and the criteria allow to evaluate several aspects or points of view of the RAF objectives. Metrics are parameters or functions used to assess the criteria. In order to facilitate the RAF application, objectives were further grouped into two main dimensions.

The RAF seeks also to ensure the alignment with asset management, taking into consideration the fundamentals of value of the assets, leadership in service provision, assurance of alignment in the organization and of resources for effective implementation of a plan, along with the RAF application in the short and long term [37]. These conditions are incorporated in metric´s definition. The main *attributes* for an adequate urban resilience assessment (e.g., metric´s reference values ought to be defined) and the main *aspects* to be evaluated in the NBS (e.g., infrastructure management), identified in the literature review [31], are also considered.

The development of the RAF was performed in five main steps—i) identification of the urban resilience dimensions in the RAF; ii) definition of objectives, criteria, and metrics (O-C-M); iii) validation of the O-C-M of the RAF; iv) definition of reference values for each metrics; and v) consolidation of the RAF. The focus of this paper is on the methodology's first four steps.
