- The upper main valleys: Zone of later complex changes of process and form

Physical changes in the upper main valleys were similar to those in tributaries, the main differences being that they came later, were less violent, and the sediment texture was generally finer. As explained in Chapter 3, these reaches were prolific net sediment sources from about 1940 until recently. As in the tributaries, the current prognosis is general stability with perhaps a mild accumulation of sediment in the future. Again, both villages and farms were severely affected.