Management of suspended solids accumulation on a tidally inundated stormwater canal

Abstract

Low-relief coastal cities have experienced increased flooding due to climate change. During high tides or swell surges, stormwater canals or pipes can be inundated by coastal waters, causing suspended solids to accumulate at the conduits’ outfall. The Chilean city Valparaiso is currently upgrading its stormwater network with costly underground stormwater aqueducts such as the coastal Argentina stormwater canal (ASC). However, soon after the ASC was put in operation, seawater intrusion and bidirectional flow at the lowest sectors of the canal decreased its water-conveying capacity, and suspended solids that otherwise would have been carried to Valparaiso Bay accumulated in the lower sectors of the canal, close to its outfall. Urban growth and a reduction in pervious land covers could worsen the current situation. Therefore, the current ASC outfall seems to be an unsustainable solution for the conveyance of rainwater and suspended solids. In this article, a hydrodynamic model of Valparaiso Bay and the ASC is presented and the current ASC hydrodynamic regime is described. The validated hydrodynamic model was used to explore the feasibility of using a submarine outfall to transport the accumulated muddy water to an offshore location. The effects of sea-level rise on the existing stormwater canal were studied and its potential to further prevent efficient conveyance of rainwater from the city to Valparaiso Bay was explored.