The Riparian Zone is the very sensitive region surrounding a stream. Vegetation growing here helps to produce bugs, which are a staple diet for fish living in the stream. A lack of vegetation not only hampers this, but also is a major cause of steam-bank erosion. Rain and run-off water is absorbed into the ground, and seeps slowly into streams, over a long period of time. Covering riparian areas (e.g., with black-top, etc) causes run-off to flow directly into the stream, and may cause flash-floods and inconsistent water flows. In an urban setting, riparian zones can act as pathways for wild animals to move from one watershed to another.