Complex Adaptive System Approach for Studying the Impact of Externalities on the Success of Restoring Stream Functions

Abstract

The overarching goal of stream restoration projects is to foster the adaptive capacities of stream functions while maintaining their resilience to excessive stresses. This paper introduces a methodology for evaluating the impact of stream restoration design strategies on multiple stream functions. The proposed method implements a functions-based, conceptual model of stream restoration based on the theory of complex adaptive system and agent-based modeling. The model illustrates the variable responses and stream functions recovery under different sets of initial conditions and stresses imposed on the system. For purposes of illustration, a systematic procedure is outlined to demonstrate the model application for quantitative risk assessment of stream functions. The results showed that the stream functions respond and adapt based on the removal of stressors and externalities and type of management intervention. However, some of these functions undergo these changes at slower rate and may take decades to recover. A balanced investment in watershed management with reach-scale restoration is recommended to reduce, to the maximum extent practicable, stressors impacting stream health and achieve desired goals and outcomes.