I am interested in learning about practical methods to reduce the effect
of local katabatic flow in making low lying areas cooler and more
susceptible to frost. There are many references that cold air can be
trapped in low lying areas and that landforms, hedges, windbreaks,
embankments etc can affect the flow of cold air and hence the frost
effect.

Most advice seems to be along the lines of "don't plant frost tender
crops in hollows" or "plant in hollows later in the spring". Can
anybody give me a reference to practical advice on how to use hedges,
windbreaks etc to reduce the effect, ie by directing the cold flow away
from your crop.

David