Towards predicting the initiation of overland flow from relatively flat agricultural fields using surface water coverage

•Overland flow from relatively flat land is largely controlled by hydrological connectivity.•Hydrological connectivity is difficult to monitor / measure in real time.•We propose surface water coverage (ASW) as a proxy for hydrological connectivity.•A clear threshold response of overland flow to ASW was observed.•ASW has substantial potential for the prediction of overland flow initiation.