Stream flow velocity measurement with smartphones: a technique for citizen observatories, decision-making, and water management

Stream flow velocity may be used for estimating discharge. Given the relative scarcity of direct stream flow and discharge measurements, surface velocity measurements can provide useful information for flood warning, hydropower production, hydrological science in general and water resource management. Some recent research efforts attempt involving the population in environmental sensing to complement existing static monitoring networks with alternative, spatially dense environmental information. Given the availability of sensing and the advances in image processing techniques (smartphones), there is a large potential to obtain hydrologically relevant data through motivated citizens. In this study, we investigate the feasibility of stream flow surface velocity measurements from movie clips taken by (smartphone) cameras based on specifically adapted image processing techniques. Results from movie clip derived velocity information is presented and compared to reference measurements from standard flow meters in various field experiments. The application of this technology in the context of so-called Citizen Observatories is expected to have a significant impact on hazard warning, forecasting, decision-making and water governance.