Rocks erode, travel down rivers and eventually in the form of small particles, settle in river deltas and estuaries. Even smaller pieces can be carried hundreds of miles into the ocean. It’s all part of the natural process of sedimentation, but like many other natural cycles, this one has been hijacked by human activities. Development, agriculture, channelization of streams, damming and many other practices change the natural course of sediment in the coastal oceans more than the ecosystem can handle.
These changes can either be a drastic increase in sediment runoff from upstream sources or a complete deprivation of naturally occurring deltas. In addition, many pollutants cling to these sediment particles so that changing the location of the sediment also shifts the location of pollution.