Flood pattern changes in the rivers of the Baltic countries

Estimation of both the frequency and variation of spring floods is a key issue for the assessment and management of flood risks. Changes in river floods in Estonia, Latvia and Lithuania have been investigated in few national studies. However, there are no studies of the changes of flood patterns by using a common methodology for the rivers of this region. In this study flood pattern changes in the rivers of the Baltic countries were estimated applying trend and frequency analysis for the periods of 1922–2010, 1922–1960, 1961–2010 and 1991–2010, i.e. for the whole spring flood data sets, periods before and after 1960 (this year was considered as the beginning of the remarkable climate change), as well as for the two past decades. A comparative study of five probability distributions was performed in order to estimate which distribution at best represents statistical characteristics of the flood data. The results showed that maximum discharges of spring floods decreased over the whole studied period. Only some insignificant positive trends of maximum discharges were found in the last time period in continental and transitional rivers. Generalized extreme value distribution provided the best approximation to the maximum discharge data series of the rivers of Baltic countries for the whole observation period. First published online: 08 Jul 201

Documentary evidence of past floods in Europe and their utility in flood frequency estimation

International audienceThis review outlines the use of documentary evidence of historical flood events in contemporary flood frequency estimation in European countries. The study shows that despite widespread consensus in the scientific literature on the utility of documentary evidence, the actual migration from academic to practical application has been limited. A detailed review of flood frequency estimation guidelines from different countries showed that the value of historical data is generally recognised, but practical methods for systematic and routine inclusion of this type of data into risk analysis are in most cases not available. Studies of historical events were identified in most countries, and good examples of national databases attempting to collate the available information were identified. The conclusion is that there is considerable potential for improving the reliability of the current flood risk assessments by harvesting the valuable information on past extreme events contained in the historical data sets.Cet article présente une revue de l'utilisation de l'information documentaire sur les crues historiques par les pays européens pour l'analyse fréquentielle des crues. L'étude montre que, malgré l'existence d'un consensus scientifique sur l'intérêt de ce type d'information, son utilisation reste encore limitée d'un point de vue opérationnel. Si les guides pratiques sur l'estimation des crues mentionnent en général bien l'intérêt de l'information historique, il existe encore peu de logiciel disponible utilisant cette information. Des travaux sont en cours dans plusieurs pays pour constituer des bases de données nationales sur les crues historiques. La conclusion est qu'il y aurait un fort bénéfice à exploiter ces informations pour l'estimation du risque de crue