Heavy Sediment deposits affect waterways because it can fill in drains, lakes, rivers, and sewage blockage. Sediment loss affects land and soil quality because it can mean a loss in nutrients that the land may need for vegetation. It can also cause flooding, which can carry toxins into water ways.
Well if you mean what does the controlled part of a scientific investigation, it is the part of the investigation that will be your control or your base, untouched, original, data and such.
