I think you have set up experiments in different sites say agriculture, settlements, forests, etc., and record or measure the total surface runoff for at least 3 years. It will be totally empirical research whereby you generate the primary data and draw logical conclusions. So, discuss with your supervisor, select suitable sites, devise the mechanism to measure the surface runoff data, and start the work. The outcomes will greatly helpful for the planning and development of the study area that you have chosen.
Be aware of safety when choosing sites and whether you will be able to access them during the events you want to measure. Stability is also an issue, as many channels are constantly changing.
Interesting parameters to study would be flow, sediment transport, and water quality. Using benthic macro-invertebrates as a proxy for water quality is cheap and relatively representative of the sample. There are many publications regarding methods of collecting flow and sediment samples.