by Gilly Brewster
(Los Angeles, California, USA)
What nature lover does not feel soothed and refreshed by the cheerful rushing of a mountain stream or the soft babbling of a meadow brook. These sounds are indeed music to our ears.
Following along a stream on a mountain hike or on a stroll in the countryside, especially if the stream is unspoiled and abounding with wild plants and animal life.
But today finding such walks is not all that easy. Streams have fared no better than other natural bodies of water—ponds, lakes, ditches, and swales. They have been straightened out, covered over with pavement, misused as dumping grounds, or they have simply disappeared.
Why not recreate some of the much sung beauty and romance of astream in your backyard by setting up a stream bed there? For even in a garden, a stream offers fascinating possibilities for planting, acts as a biological filter, and, more important, provides a place to live for many creatures.
Streams in Nature
In nature no stream is quite like any other. Natural streams—if they have not been degraded into artificial, straight channels—are as varied as the landscapes they traverse.
Even a single stream exhibits variety as it runs from its source to its destination. Each section of its course presents a different aspect, displaying its own characteristic plant and animal populations.
All streams have three features in common: water that flows downward; a source, which marks the upper end of the stream’s surface course; and a lower end or mouth. A stream can flow into another stream or river or into a body of flat, or lentic, water. Or it may disappear from view, make its way underground for a while, and either reappear again farther downstream or drain into the ground water.
We can divide streams roughly into two types:
Mountain Streams: These are characterized by a strong gradient and a rocky bottom, with the result that the water rushes down at a great speed. It is possible to distinguish several subtypes, such as alpine streams, hill country streams, and glacial streams.
Meadow Brooks: Typically, meadow brooks have a low gradient and a sandy to pebbly bottom. What is often striking about them is their curving course. Since at a low gradient water moves slowly, obstacles cause bends and detours in the stream’s course; the stream, we say, meanders.
Some of these obstacles are created by the stream itself. After heavy rains or when the snow melts in the spring, water volume and speed of flow can increase dramatically, and the stream may carry along objects like downed trees for a distance, later depositing them in its own path, and then a new way has to be found around them.
There are no general rules about the length and width of streams. The length is often hard to determine because streams may run underground for a stretch now and then. The width can be anything from a narrow rill to a few feet or much more. It is hard to say at what width a stream is more properly called a river. Experts use the volume of flow to help decide whether a body of moving water is a largestream or a small river.