Stream geomorphology, or the forming of land by streams, occurs because of a series of complex processes that are not easily described by scientific theories. The most basic concept is that of force and resistance. Running water exerts force on the landscape and, in turn, the landscape offers resistance to this force. If the exerted force is less than the resistance, there is no change. If, the force is greater than the resistance, there is change to the slope or stream channel. We call this change geomorphic work.
A poor understanding of these processes and inadequate consideration of the influence of changes that occur on the landscape and within the floodplain can cause a variety of adverse outcomes.
Particular attention needs to be paid to the potential impact on a stream of: (a) land use changes that reduce vegetation and increase the amount of impervious area; (b) activities that modify the floodplain; (c) the construction of culverts and bridges; and (d) activities that are designed to modify the characteristics of the main stream channel. Any one of these activities might disrupt the equilibrium resulting in rapid and often undesirable adjustments.
Successful stream stewardship requires combining this knowledge with sound engineering and scientific principles, together with an understanding and appreciation of the ecology of the stream and its interaction with the landscape.
While there is considerable debate on this topic, we use the term stream to refer to any channel and floodplain system that may have competing uses, but aquatic habitat improvement is a primary goal.