On the causes in the contemporary decline in the gully head retreat rates in Udmurtia

© 2018 Russian Academy of Sciences. All rights reserved. Results of long-term monitoring of gully head retreat rates (GHRR) during almost the entire recent phase of global warming (1978-2014) in different parts of the Udmurt Republic are analysed. Assessment of the influence of different climatic parameters on GHRR in different parts of Udmurtiya and the whole territory in the two time intervals (1978-1997 and 1998-2014) is the main content of article. It was determined that GHRR decreased from 1.3 m yr-1 in 1978-1997 to 0.3 m yr-1 in 1998-2014. Based on the observation data that have been collecting nearby Izhevsk twice a year (after snow-melting and in autumn after period of rain-storms events), some changes were found in the relative contribution of snow-melting and rainfall events to GHRR. Some 80% of gully head retreat was occurring during the snow-melt season in the period 1978-1997, and only 53% - after 1997. Increasing influence of the rain-fed runoff manifested more clearly in the eastern and northern parts of the Vyatka-Kamsa interfluve, while in the West, higher correlation was found between GHRR and frozen soil depth in winter. The most significant increase of gully length occurs during the warm part of the year and is related to rains that produce daily precipitation layer of >40 mm