One of the main, if not the main, source of sand to the coast is fluvial sediment supply. Any change in the sand supplied to the coast will disturb its equilibrium state, potentially leading to coastline recession (with a decrease in fluvial sediment supply) or coastline progradation (with an increase in fluvial sediment supply). Given ongoing human activities in basin areas (e.g., agriculture, hydropower dams, new/expanding human settlements) and climate change, many of the world's low elevation coastal zones are at risk of losing land and rich bio-diversity therein. In this context, hydrological model investigations are required to assess the impacts of climate change and relevant human activities on fluvial sediment supply to coasts. However, in data-poor areas, the standard approach of using a wellcalibrated/ validated process-based hydrological modelling for impact assessment is challenging due to the limited availability of observed data.The overarching objective of this study is to investigate how different modelling approaches and input data sources may influence projections of streamflow and fluvial sediment loads accounting for climate change and human activities, particularly in data-poor basins. In order to achieve this overarching objective, two case study sites were selected: Irrawaddy River Basin in Myanmar and Kalu River Basin in Sri Lanka. Compared to other major river systems in Southeast and South Asia, the main rivers of these two basins can be considered to be unregulated. However, future flow regimes in the two basins could change significantly due to proposed development activities. These changes can be further exacerbated due to impacts of the extreme weather conditions, which are quite frequently observed in these regions, and due to climate change effects.