Storage or parking areas are not required to be paved; however, any boat, recreational vehicle or hauling trailer must be parked or stored or driven to and from said parking or storage area on a dust-free and rut-free surface, including without being limited to any such areas covered with grass, ground cover, water per-permeable grass pavers, cement, asphalt or other similar ground cover. Parking, storage or driving on gravel or exposed dirt is prohibited; however, driving on a gravel driveway that has been previously established as a lawful nonconforming use is permitted.