UC Davis

Urbanized riverscapes are vulnerable to changing flow and sediment regimes with consequences including increased flooding and habitat degradation. The conventional engineering solution in this situation involves gray infrastructure, including concrete-lined trapezoidal channels and flood-prevention structures, retention and detention ponds, and closed subsurface piped systems. Gray infrastructure is failing to mitigate flooding under changing climate conditions, particularly in coastal regions impacted by rising sea levels, and it is well understood to eliminate essential, natural ecosystem functions and services. This study presents a multidisciplinary design framework to support adaptive riverscape planning with additional and complementary modeling applications. It integrates synthetic 3D rivers and real-world topographic data for design development, testing and selection, refinement, and presentation to yield project-specific alternatives to gray infrastructure while enhancing stakeholder engagement. The framework was applied to a semi-alluvial urban stream as a coastal case study. Three river-design scenarios were developed upstream from a flood-prone urban site to improve water retention and soil infiltration while reducing downstream flow rates for enhanced flood mitigation. Improved river-design outcomes are demonstrated by modeling flow velocity and water depth to test hydraulic responses to river-designs. Sediment transport models are presented to understand how river-designs may adapt to elevation change and the geomorphic-form-variation approach is applied as a measure of habitat heterogeneity. The framework's flexibility is showcased by revising a river-design and re-simulating hydraulic responses to new surface-form configurations. We also present a rendered perspective image to illustrate a tool available for communicating a nature-based solution action in urbanized contexts. The framework can be adapted to diverse urban riverscape projects that require hydraulic, geomorphic, ecological, and social trade-offs by supporting a collaborative planning approach for nature-based solutions.