During the lnterreg Polder2Cs project overflow tests on a grass sloped levee have been executed. This dataset contains the raw data of the overflow tests executed in November 2020 on test stretches B_OFl, B_OF2, B_OF4 and B_OFS in the Belgian part of the Hedwige and Prosperpolder and on test stretches NL_OFl and NL_OFS ln the Dutch part of the Hedwige and Prosperpolder. Measurements of water level and flow velocity were executed (time series}. With the camera system, the damage of the grass cover layer and also the water flow (with low frequency camera monitoring} during the tests were measured. Also some manual drawings of the damage of the grass cover layer were made. For the different test stretches, the raw data contain data of damage recordings, recordings of the water flow and some damage drawings.