Alpha Angle & Beta Angle
Alpha Angle & Beta Angle : Also: Angle of Reach & Runout Angle respectively. The alpha angle is the angle between the horizontal and a line drawn from the highest point of the crown face to the toe of the debris. Alpha can be measured for an individual avalanche, but it is more commonly calculated for a specific return period. Extreme values of alpha (such as 100 years) can be determined from historical records, tree ring data, or statistical methods. The alpha angle is also termed the angle of reach or the rounout angle. For 100 year avalanches this angle typically ranges from about 18 to 22 degrees. The beta angle is the angle measured to the top of the starting zone from the place where the slope first becomes 10 degrees (locally). This is a terrain feature of the particular path and is not differenct for different events, as the alpha angle is. An extreme event alpha angle (such as that of a 100-year avalanche) can be estimated from a beta angle using statistical methods, but the parameters vary from one mountain range to another (independent of prevailing climate)
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