A reach in geography is an expanse, or widening, of a stream or river channel. This commonly occurs after the river or stream is dammed. A reach is similar to an arm.

It can refer to:-

• An extended portion or stretch of land or water;
• a straight portion of a stream or river, as from one turn to another;
• a level stretch, as between locks in a canal;
• an arm of the sea extending up into the land.