Search Results (4)

Alluvial sedimentary records in the North China Plain are essential in expanding flood history and understanding hazard patterns in the Yellow River basin where inundation risk exists and would probably increase under future global change. A detailed study of the Longwangmiao profile in the lower Yellow River floodplain reveals ancient flooding records over the late Holocene. Slackwater deposits are distinguished by typical sedimentary features and share similarities with those in the upper and middle Yellow River. This indicates that the traditional method can still be applied for paleoflood research beyond the gorge. However, unlike confined bedrock gorges, multiphase flood deposits of slackwater and overbank deposits represent different stages of flood events. These sedimentary assemblages recorded six flooding periods, further confirmed by the analysis of grain size and geochemistry. The profile was broadly subdivided into two flood-poor phases (3.7–6.7 ka, 0.8–1.7 ka) and three flood-rich phases (before 6.7 ka, 1.7–3.7 ka, after 0.8 ka) based on the dating results. Compared with the existing related research in the nearby area, the synchronous deposition cycles of floods and inter-floods are mainly controlled by the hydrodynamic conditions of the old Yellow River course. This study provides an analogue of paleoflood research in the lower Yellow River and similar alluvial plains. It explores the potential of interlinking paleoflood records in the whole Yellow River basin. Full article

Coastal Peru, one of the driest deserts in the world, is a key region to investigate the connection between climate processes and Earth surface responses. However, the trends in space and time of the landscape effects of El Niño events throughout the last millennium are hard to outline. A deeper understanding of geological and archaeological data in pre-Hispanic time can help to shed light on some critical questions regarding the relationship between such a coupled atmosphere–ocean phenomenon and landscape modifications. The bibliographic sources required for this purpose are scattered throughout various disciplines, ranging from physical to human sciences, and thus comprehensive databases were used to identify and screen relevant studies. The performed examination of these documents allowed us to assess strengths and weaknesses of literature hypotheses and motivate additional studies on targeted research objectives. Full article

Lake sediments are a valuable archive to document past flood occurrence and magnitude, and their evolution over centuries to millennia. This information has the potential to greatly improve current flood design and risk assessment approaches, which are hampered by the shortness and scarcity of gauge records. For this reason, paleoflood hydrology from lake sediments received fast-growing attention over the last decade. This allowed an extensive development of experience and methodologies and, thereby, the reconstruction of paleoflood series with increasingly higher accuracy. In this review, we provide up-to-date knowledge on flood sedimentary processes and systems, as well as on state-of-the-art methods for reconstructing and interpreting paleoflood records. We also discuss possible perspectives in the field of paleoflood hydrology from lake sediments by highlighting the remaining challenges. This review intends to guide the research interest in documenting past floods from lake sediments. In particular, we offer here guidance supported by the literature in how: to choose the most appropriate lake in a given region, to find the best suited sedimentary environments to take the cores, to identify flood deposits in the sedimentary sequence, to distinguish them from other instantaneous deposits, and finally, to rigorously interpret the flood chronicle thus produced. Full article

Toxic trace metals are a common and significant contaminant in riverine ecosystems, and are derived from both natural and anthropogenic sources. Determining the contributions of metals from these sources has proven difficult, in part, because physical and biogeochemical processes alter the nature (e.g., grain size, mineral composition, organic matter content) of the source materials as they are transported through the drainage network. This study examined the use of paleoflood deposits located along the hyperarid Rio Salado, a tributary to the Rio Loa of northern Chile, to construct local background functions and enrichment factors (LEFs) to differentiate between natural and anthropogenic metal sources. Significant variations in metal content occurred between river reaches and flood deposits of a given reach; these variations were primarily related to changes in sediment source that may reflect differences in El Niño and La Niña precipitation patterns. Three conservative elements (Al, Fe, Co) were examined to construct background functions for seven trace metals. Cobalt yielded the most effective background functions for As, Cd, Ni, Pb, and Zn; Fe was selected for Cr, and Al for Cu. The resulting LEFs approximated 1, illustrating that paleoflood deposits produced effective background functions, and could be applied to downstream sites contaminated by mining activity. Full article