ABSTRACT
The measurement of variables such as cliff recession, temperature or soil movement in an already established temporal framework involves such issues as the method of sampling in time, including regular or irregular spacing of records, the frequency of observation and the types of ‘observational clocks’ available against which to standardize the information. Continuous or regular discrete observations are still relatively uncommon in geomorphology because of the heavy demands they make on cost and labour. On the other hand reports of past events, their magnitudes and period of operation are generally more available. From this data and from the spacing of events from continuously recorded data a body of information called recurrence time is available. Here time is the variable of interest and is measured between occurrences of the event. Records of runoff, sediment yield, precipitation, snowfall, water quality and many other variables are now being collected all over the world for management or research purposes.
