Hydrological thresholds and basin control over paleoflood records in lakes

Abstract

The scarcity of long-term hydrological data is a barrier to reliably determining the likelihood of floods becoming more frequent and/or intense in a warmer world. Lake sediments preserve characteristic event layers, offering the potential to develop widely distributed and unique chronologies of historical floods. Inferring flood magnitude remains a greater challenge, previously overcome in part by analyzing sharply laminated polar or alpine sequences. Here we demonstrate an approach to obtain flood frequency and magnitude data from an unexploited resource, the largely visually homogeneous, organic sediments that typify most temperate lakes. The geochemical composition and end-member modeling of sediment trap and adjacent short core particle size data for Brotherswater (northwest England) discriminates the signature of infrequent, coarse-grained flood deposits from seasonal and longer term allogenic (enhanced discharge and sediment supply during winter) and autogenic (summer productivity, thermal mixing) depositional processes. Comparing the paleoflood reconstruction to local river discharges shows that hydrological thresholds censor event signature preservation, with 4 yr recurrence intervals detectable in delta-proximal sediments declining to 9 yr in the lake center. Event threshold (discharge) and process characterization are essential precursors to discerning flood magnitude from sediment archives. Implementation of our approach in globally prevalent temperate lakes offers a vast, unique repository of long-term hydrological data for hydrologists, climate modelers, engineers, and policy makers addressing future flood risks.

Quantifying system disturbance and recovery from historical mining-derived metal contamination at Brotherswater, northwest England

“…Company documents indicate processing was moved to Greenside Mine and more efficient and mechanised ore extraction techniques were employed, capable of harvesting a greater proportion of the ore from the host rock and leaving less surface waste (Tyler 1992). Pb continued to fluctuate after the cessation of mining in 1942: subsequent peaks probably relate to the remobilisation of mining waste during flood events in the 1960s (Schillereff et al 2014(Schillereff et al , 2016. Any atmospheric signal from leaded petrol in automobiles during 1950-1970(von Storch et al 2003 was likely masked by the particulate flux from the catchment.…”

High resolution lake sediment record reveals self‐organized criticality in erosion processes regulated by internal feedbacks

“…The peaks in silt accumulation over the last 150 years follow the history of peak annual streamflow (Figure ). The five largest floods ( ad 1965, 1997, 1956, 1974, and 2006) are close in time to some of the largest reconstructed erosion events ( ad 1965, 2007, 1961, 1975, and 1954) suggesting sensitivity of our site location to the magnitude of recurrent floods (Schillereff et al ., ). Earlier historic floods pre‐dating the gage‐station record (in ad 1861, 1890, and 1927) are close in time to other reconstructed erosion events, especially considering dating uncertainties (Figure ).…”

“…Lake sediment archives can be used to extend the record of individual sediment flux events through the reconstruction of event stratigraphies (Thorndycraft et al ., ), which, in records that span millennia, can be used to infer magnitude and frequency relationships of rainfall/flood events (Czymzik et al ., ; Glur et al ., ; Swierczynski et al ., ). High resolution lake‐derived erosion histories often indicate that centennial to millennial scale climate variability may exert a first‐order control over the magnitude of erosion rates (Lamoureux, ; Meyer and Pierce, ; Pierce et al ., :, Schillereff et al ., ). However, while lake sediment records provide important data on magnitude and frequency of individual sediment delivery events triggered by rainfall (Glur et al ., ; Swierczynski et al ., ; Schillereff et al ., ), the relationship between erosion events and climate can be difficult to disentangle because sediment delivery may be mediated by other landscape scale processes (e.g.…”

“…High resolution lake‐derived erosion histories often indicate that centennial to millennial scale climate variability may exert a first‐order control over the magnitude of erosion rates (Lamoureux, ; Meyer and Pierce, ; Pierce et al ., :, Schillereff et al ., ). However, while lake sediment records provide important data on magnitude and frequency of individual sediment delivery events triggered by rainfall (Glur et al ., ; Swierczynski et al ., ; Schillereff et al ., ), the relationship between erosion events and climate can be difficult to disentangle because sediment delivery may be mediated by other landscape scale processes (e.g. fires or earthquakes), which can overprint (or even offset) the climatic control over erosion dynamics (Figure ).…”

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

“…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).…”