Cp. Quine et Ims. White, USING THE RELATIONSHIP BETWEEN RATE OF TATTER AND TOPOGRAPHIC VARIABLES TO PREDICT SITE WINDINESS IN UPLAND BRITAIN, Forestry, 67(3), 1994, pp. 245-256
Tatter flags have been used for more than 30 years to measure wind exp
osure of forest sites in upland Britain. A re-analysis of tatter flag
data from 1111 sites was performed to investigate factors influencing
site windiness. At each location flags had been flown for periods of 2
months, and six consecutive bimonthly readings were combined to provi
de an annual estimate of tatter. Average daily tatter rate was related
to geographic position, aspect, elevation, topex, valley shape and va
lley direction. The aspect, valley shape and valley direction were all
derived from the eight topex sector values; they provide a more detai
led treatment of topography than previous studies and include a measur
e for funnelling of wind in valleys. The proportion of variance explai
ned by the regression was 80 per cent. The regression has been used to
develop revised windiness scores for the Windthrow Hazard Classificat
ion and could be used to estimate site windiness for site-yield and re
lated studies. Digital terrain models can calculate the required site
variables. Further investigations to improve the estimates are discuss
ed.