Numerous factors affect streamflow, and therefore the potential for flooding. Most important are the amount and type of precipitation, the nature and condition of the drainage basin, and climate.
All rivers are subject to fluctuations in flow.
During a rainstorm, the amount, intensity, duration, area of storm, and path of the storm, all influence the runoff reaching the stream. The amount, intensity, and duration of storms affect the ability of the land to absorb the precipitation and therefore affect the rate of runoff. The area and path of the storm relate to the area of the basin receiving rainfall, which in turn, represents the area contributing runoff. The area and the runoff rate determine the volume of water that will pass a given point downstream. The shape, size, soil type, and topography of the drainage basin are other factors affecting the quantity of water reaching the stream.