Saturated overland flow

Surface runoff. Hydrologists have identified two processes for generating surface runoff over land. The first, saturated overland flow (SOF), is generated when precipitation (or snowmelt) occurs over a saturated soil since water has nowhere to infiltrate, it then runs off over land. SOF typically occurs only in humid environments or where the water table rises to intersect with a stream. Horton overland flow (HOF or infiltration-limited overland flow) occurs when precipitation intensity exceeds the infiltration capacity of the soil in a non-saturated environment. In this case, only the excess precipitation (that exceeding the infiltration capacity) runs off over the surface. Both types of overland runoff generate relatively rapid flows that constitute the surface water contribution to the hydrograph (Fig. 6-6). 

Fig. 8-7 Three principal ratios control the style of runoff generation prevalent in a landscape (1) ratio of rainfall intensity to the infiltration capacity of the soil (2) ratio of bedrock conductivity to soil conductivity and (3) the topographic index defined by the ratio of the upslope drainage area to the ground slope. HOF = Horton overland flow SOF = saturation overland flow SSS = subsurface stormflow GWR = groundwater flow.

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