A dishwashing appliance may include a cabinet, a tub, a spray assembly, a circulation pump, a pressure sensor, and a controller. The circulation pump may be in fluid communication with a wash chamber defined by the tub. The pressure sensor may be upstream of the circulation pump. The controller may be configured to initiate a washing operation including activating the circulation pump, detecting movement of the door from a closed position, detecting return of the door to the closed position, calculating a modified time period for flood detection, determining pressure at the pressure sensor exceeds a pressure threshold following detecting return of the door to the closed position, initiating the modified time period in response to determining pressure at the pressure sensor exceeds the pressure threshold, and directing the circulation pump based on measuring the elevated pressure and expiration of the modified time period.