Egypt's deserts are about the perfect climate for preserving wood. However the area near water is not desert and so not perfect. Boats would be moved, but the piers (such as they were in those days, I doubt we are talking a modern shipyard structure) would remain in the water, and in general when a river moves the area remains a swamp long enough for any wood to rot.
The type of wood used maters, some wood rots much faster than others. Boats would have been made from rot resistant wood since they are in the water. I wouldn't be surprised if they used any old wood for the piers since the water course and floods mean the piers need to be rebuilt every year anyway - but this is pure speculation.
The type of wood used maters, some wood rots much faster than others. Boats would have been made from rot resistant wood since they are in the water. I wouldn't be surprised if they used any old wood for the piers since the water course and floods mean the piers need to be rebuilt every year anyway - but this is pure speculation.