sentences:  They also disrupt the long shore transport of sediment through the construction of piers, marinas or groynes, breakwaters and other hard structures.Excavating, building roads, houses and walkways on coastal dunes or beaches also causes sand dune erosion by disrupting natural sediment processes.Effective management of coastal dune systems must consider natural processes as a normal part of the natural environment as well as controlling human activities and seeking to alter natural processes should be kept at a minimum in order for restoration to be successful.