Estimation of sediment loadings in a small steep tropical catchment impacted by quarrying activities: a case study of the Acono River catchment, Trinidad, West Indies

On the island of Trinidad, intense anthropogenic activity and inappropriate land use on terrain vulnerable to erosion and rapid runoff lead to severe sedimentation in the watercourses. A major impact is an increase in flood risk during the strong storm events characteristic of the tropical rainy season due to reduced channel capacity. This study addresses the problem of sedimentation in the Acono River in light of the high sediment loadings observed at the outlet of a 6.6 km2 steep catchment where an operating limestone quarry is located. A hydrologic and sediment measurement network was developed to estimate the impact of the quarry on the sediment loadings in the Acono River for several storm events during a year. Results indicated that the quarry yields tremendously more sediment than the rest of catchment. The MUSLE model was used to estimate sediment yield from soil erosion for individual rainfall events and provided good results. Several sediment transport formulae were used to determine both suspended and bed load sediment discharge during rainfall events. The significant deviation of the computed values from the measured values showed how difficult it is to predict sediment discharge in natural rivers, particularly where washload is a significant component.