The relationship between annual varve thickness and maximum annual discharge (1909–1971)

Annually laminated (varved) sediments from the River Ångermanälven, mid-central Sweden, have been used to construct an annual 2000-year long record of varve thickness. Maximum daily annual discharge and mean varve thickness for the years 1909–1971 are significantly correlated (r=0.87). A relationship between maximum daily annual discharge for the observed period (1909–1971) and varve thickness was determined. The return time of two exceptionally thick varves in the 2000-year long record at the years 658 and 492 ad were estimated and their likelihood estimated based on a Gumbel frequency analysis.