Interpreting historical, botanical, and geological evidence to aid preparations for future floods

Abstract

River flooding is among the most destructive of natural hazards globally, causing widespread loss of life, damage to infrastructure and economic deprivation. Societies are currently under increasing threat from such floods, predominantly from increasing exposure of people and assets in flood‐prone areas, but also as a result of changes in flood magnitude, frequency, and timing. Accurate flood hazard and risk assessment are therefore crucial for the sustainable development of societies worldwide. With a paucity of hydrological measurements, evidence from the field offers the only insight into truly extreme events and their variability in space and time. Historical, botanical, and geological archives have increasingly been recognized as valuable sources of extreme flood event information. These different archives are here reviewed with a particular focus on the recording mechanisms of flood information, the historical development of the methodological approaches and the type of information that those archives can provide. These studies provide a wealthy dataset of hundreds of historical and palaeoflood series, whose analysis reveals a noticeable dominance of records in Europe. After describing the diversity of flood information provided by this dataset, we identify how these records have improved and could further improve flood hazard assessments and, thereby, flood management and mitigation plans. This article is categorized under: Science of Water > Water Extremes Engineering Water > Planning Water Science of Water > Methods

Monthly storminess over the Po River Basin during the past millennium (800–2018 CE)

“…provide information about social vulnerability and impacts of climate extremes that allow for direct comparison with contemporary climatology (Wilhelm et al 2018). The study of the most famous fluvial floods affecting urban settings in the Middle Ages offers a conceptual reference to overcome too rigid a distinction between natural disasters and disasters produced by human agency.…”

Using lake sediment archives to improve understanding of flood magnitude and frequency: Recent extreme flooding in northwest UK

“…Flood magnitude and frequency (FMF) analyses are used by industry to estimate the magnitude (design specification for flood protection) and risk (probability of recurrence) of floods. Typically short duration (<50 years) gauging station data underpin most FMF analyses, either directly for single stations or by pooling station series with data from other gauged stations, but neither approach presents a full picture of past flooding (Wilhelm et al, ; Macdonald et al, ; Wilhelm et al, ; Wilhelm et al, ). Incorporating additional extreme events from historical or palaeoflood archives can extend the temporal range of FMF analysis (Wilhelm et al, ; Evin et al, ) if information on both event timing and magnitude can be secured.…”

“…Flood magnitude and frequency (FMF) analyses are used by industry to estimate the magnitude (design specification for flood protection) and risk (probability of recurrence) of floods. Typically short duration (<50 years) gauging station data underpin most FMF analyses, either directly for single stations or by pooling station series with data from other gauged stations, but neither approach presents a full picture of past flooding (Wilhelm et al, 2013;Macdonald et al, 2014;Wilhelm et al, 2018a;Wilhelm et al, 2018b).…”

“…To date sedimentary palaeoflood analyses have focused typically on event timing with limited estimation of event magnitude (e.g. Schillereff et al, 2014;Wilhelm et al, 2018a;Wilhelm et al, 2018b). Whilst flood frequency data are useful for exploring the relationship between flood phasing and other climate indices (Schulte et al, 2015;Schillereff et al, 2016;Wilhelm et al, 2018a;Wilhelm et al, 2018b) without quantification of event magnitude it is challenging to calculate reliable recurrence intervals (NERC, 1999).…”

“…Schillereff et al, 2014;Wilhelm et al, 2018a;Wilhelm et al, 2018b). Whilst flood frequency data are useful for exploring the relationship between flood phasing and other climate indices (Schulte et al, 2015;Schillereff et al, 2016;Wilhelm et al, 2018a;Wilhelm et al, 2018b) without quantification of event magnitude it is challenging to calculate reliable recurrence intervals (NERC, 1999). Here, we report the first lacustrine palaeoflood record series for a large catchment in the UK and one of few applications of quantitative FMF analyses to sedimentary palaeoflood data (Evin et al, 2019).…”