an area drained by a stream is called a drainage basin, which is bounded by an imaginary line called a divide. the divide is never visible, regardless of topography. an area drained by a stream is called a drainage basin, which is bounded by an imaginary line called a divide. the divide can be clearly visible as a sharp ridge, or it could be difficult to determine in subdued topography. an area that a stream pours into is called a drainage basin, which is bounded by an imaginary line called a divide. the divide can be clearly visible as a sharp ridge, or it could be difficult to determine in subdued topography. an area drained by a stream is called a drainage basin, which is bounded by an imaginary line called a divide. the divide is always clearly visible as a sharp ridge. an area drained by a stream is called a drainage basin, which is bounded by an imaginary line called a tributary. the tributary can be clearly visible as a sharp ridge, or it could be difficult to determine in subdued topography.
