Secondly, drainage should be taken into account, use geotextiles (dorn) for its arrangement). If there are higher pieces of land near your plot, then rain water from them can flow through your property, so it is necessary to provide drainage devices. Can build sumps? And if it is floodplain? Is there a river nearby, and will it not contradict the law on the purity of water your drainage? All these issues must be resolved before starting work.