Numerical modeling evaluation of the impacts of shrimp farming operations on long-term coastal lagoon morphodynamics

Abstract

In coastal systems occupied by large clusters of pond aquaculture farms, hydro-sedimentary processes may be impacted by the combination of water management strategies that are individually performed by each cultivation unit. In this study, a numerical model was used to evaluate 100-year morphological alterations in two different idealized coastal lagoons surrounded by shrimp ponds. One is broadly based on the Guaraíras Lagoon System (RN, Brazil) where shrimp farming has developed since 1924, and the other is highly simplified to systematically investigate pond aquaculture impacts. Information obtained through numerical simulations (e.g., hypsometry changes, evolution of morphological parameters, balance of sediment volumes, bed level changes, and residual bed shear stress variations) provided coastal impact assessments for a wide variety of aquaculture occupation scenarios. Key findings include (i) water exchange operations performed by aquaculture farms are capable of modifying the morphological equilibrium state of a coastal lagoon system, especially if carried out synchronously to the local tidal oscillation; (ii) water intake operations regularly performed by pond aquaculture activity increase sediment import to the system; (iii) depth and configuration of tidal channels are modified when pond aquaculture is present. The modeling approach and analyses presented here can be extended to other systems that are under the influence of shrimp farming activity and be adopted to support novel regulations for the conservation of coastal habitats and to contribute to the sustainable development of pond aquaculture in the coastal zone.