A long-term flood discharge record derived from slackwater flood deposits of the Llobregat River, NE Spain

Abstract

Slackwater palaeoflood deposits were identified along two bedrock gorge study reaches of the Llobregat River, at Pont de Vilomara and Monistrol de Montserrat. The compiled palaeoflood record consists of two principal flood series: (a) a relatively complete record of low to high magnitude flood events from the last ca. 100 years and (b) evidence of the largest palaeoflood events that have occurred over the last ca. 2700 years. The longer term extreme palaeoflood record indicates that the discharge of the 1971 flood, the largest on record, was exceeded on at least eight occasions, with two periods of high magnitude flooding identified: (a) the Late Bronze Age (2500-2700 years ago) and (b) the Little Ice Age (AD 1500-1700). At Pont de Vilomara, palaeodischarge estimates of 3700-4300 m 3 /s compare to a discharge of 2300 m 3 /s for the 1971 event. Downstream at Monistrol, an estimate of 4680 m 3 /s for flood deposits dated as AD 1516-1642, and believed to be those of the AD 1617 flood, compared to 2500 m 3 /s for the 1971 flood. q

Quantitative historical hydrology in Europe

“…Table 1 shows a compilation of 46 case studies with historical discharge estimates at sites with multiple floods with discharge estimates published in peer review papers or being cross-checked with the original historical sources. Numerous studies suggest that current flood magnitudes are not unusual within the context of last 1000 years, with good examples for the rivers Rhine (Herget and Meurs, 2010;Wetter et al, 2011), Tiber (Calenda et al, 2005), Llobregat (Thorndycraft et al, 2005), Trent (Macdonald, 2013) and Gardon (Sheffer et al, 2008;Neppel et al, 2010). In general, the largest historical floods from the last 500 years show higher peak flows than the largest gauged floods (Fig.…”

“…In most cases, these flood marks are located in urban settings with frequent changes of the river channel topography that increase uncertainty of the values obtained when computing flood discharge. The combination of historical and palaeoflood (sedimentary) flood data has been demonstrated to be a very effective tool for improving the catalogue of past flooding and reducing uncertainties on flood discharges (Thorndycraft et al, 2005). Palaeostage indicators from sedimentary records (slackwater flood deposits) are frequently preserved within bedrock-stable cross sections which are suitable settings for hydraulic estimation of flood discharges (Benito and O'Connor, 2013).…”

“…Moreover, the age uncertainty of numerical dating (radiocarbon respectively optically stimulated luminescence methods) used in palaeoflood studies may be refined based on known documentary floods (Medialdea et al, 2014). The SPHERE project has revealed the complementary of palaeoflood and historical flood information with major gain on the quality of past flood records in terms of time and discharge, as is demonstrated in the studies performed for the rivers Gardon (Naulet et al, 2005;Sheffer et al, 2008), Ardèche (Sheffer et al, 2003;Naulet et al, 2005), Llobregat (Thorndycraft et al, 2005), and Guadalentin (Benito et al, 2010;Medialdea et al, 2014). Recent palaeoflood reconstructions from floodplain sediments have analysed geochemical proxies from continuous alluvial records and investigate local documentary flood data to calibrate the palaeohydrological records (e.g.…”

Beyond the gorge: Palaeoflood reconstruction from slackwater deposits in a range of physiographic settings in subtropical Australia

“…Large floods may not have occurred during the short gauging period and, in cases where they have, are often not recorded accurately because of flood damage and/or destruction (Baker et al, 2002;Benito et al, 2004;Thorndycraft et al, 2005). In data-rich regions, statistical analyses of regional databases have reconstructed periods of enhanced flooding in Europe and the USA (Macklin et al, 2006;Hoffmann et al, 2008;Harden et al, 2010;Thorndycraft et al, 2012;.…”

Estimation of peak discharges of historical floods

“…Note that in several previous publications (e.g. Benito et al, 2010;Brázdil et al, 2006;House et al, 2002;Thorndycraft et al, 2005) the term "palaeoflood" is used even for recent flood events quantified by means of indirect methods due to missing gauging stations. According to the established used of the prefix "palaeo", based on the oldGreek origin palaios, meaning "old" (e.g.…”