Evaluation of a new method for assessing resilience in urban aquatic social-ecological systems

Urban aquatic social-ecological systems (SESs) comprise socio-technical elements, the built environment and its management, and natural elements (water bodies) that provide ecosystem services. Changed hydrology, poor stormwater quality, and the modification of water bodies associated with urban development brings challenges for maintaining ecosystem services provision in an urban aquatic SES. Water sensitive urban design (WSUD) has emerged as a form of development that aims to better support the provision of ecosystem services. Resilience concepts provide a basis for discriminating between WSUD and conventional development approaches. Building on an existing decision support system, a new, preliminary method for assessing resilience based on the combination of the socio-technical capacity (STC) and natural capacity (NC) of urban aquatic SESs has been developed. The STC score reflects a multicriteria assessment of the characteristics of stormwater infrastructure and management. The NC score reflects an assessment of the state and trajectory of biophysical attributes of the system associated with the provision of ecosystem services. By modeling a series of future urban development scenarios in Auckland, New Zealand, the method has been shown to discriminate between scenario outcomes within constraints associated with the biophysical and built characteristics modeled. Results are consistent with key concepts of resilience theory: outcomes are grouped in regimes and exhibit hysteresis, with the ability of WSUD to improve the state of the system strongly influenced by the presence of legacy effects. The method provides a source of additional, valuable information that complements other indicators by providing a snapshot of the interaction of catchment management effort and outcomes and indicating the likely future state of the SES. Recognizing that the method is limited to providing a relative assessment of resilience and adopts certain simplistic assumptions, further research aims to investigate assessment methods that consider other, fundamental biophysical and social properties of urban aquatic SESs.