Several studies shown that crop location on arable land in a catchment significantly influences the amount of runoff at the outlet of the catchment. Modification of crop location can thus be a way to reduce damage caused by runoff as flooding of properties. Crop location depends on decisions taken at farm level. Studies conducted in Northern France about farmers’ decision-making shown that cash crops farmers differed in their leeway to modify crop location a given year. Leeway depends on farm territory characteristics, crops requierment and farm cropping plan. In these previous studies, farmers’ leeway is expressed by the proportion of farm arable land suitable for different crops to be sown. This proportion is assessed from farmer’s decision-making simulation. This method is precise but the disadvantage is that it is long to implement and that it requires a lot of information concerning crop management in the analysed farms. This paper proposes a simpler and quicker method enabling to assess whether there are or not leeway to modify crop location in a given farm. The proposed method consists in calculating an indicator based on the knowledge of the farm cropping plan and the elementary agronomic rules of crop location (i.e. for a given crop: cultivable area, waiting period and possible preceding crops). The indicator gives the proportion of crops that can be sown in several fields. Firstly we calculated this indicator for the 14 main farms of the Bourville catchment (Pays de Caux, Upper-Normandy, France) with specific agronomic rules given by each interviewed farmer. According to the indicator farms were separated into two groups: four farms with almost no leeway to modify crop location and ten farms with potential leeway. A comparison of this classification with a more precise analyse available from a previous study (based on farmers’ decision-making simulation) showed that this simpler assessment methodology is reliable. Secondly, we assessed farmers’ leeway with agronomic rules common for all farms. Indeed, some rules given by certain farmers were more restrictive than rules given by the other farmers: this led to minimise leeway. This second classification showed that leeway are more important in most of the farms, but still different from one farm to another. These differences are due to the different characteristics of farms territories and farms cropping plans.