River Systems and Environmental Change

Abstract

Linking river behaviour and drainage basin evolution to Quaternary environmental change, most notably the effects of climatic variability, tectonics, and human activity on runoff and sediment delivery, has a long history of research in the Mediterranean areas of Europe, North Africa, and the Near East. This field of research was initially stimulated by the (re)discovery at the beginning of the twentieth century of many Classical Period remains buried by river alluvium; perhaps the best known of which is the site of Olympia in western Greece (Huntington 1910). The widespread evidence for large-scale shifts in river channel positions and the rapid growth of deltas and coastal alluvial plains in historical times (Judson 1963; Raphael 1973; Kraft et al. 1980; and Chapter 13) also provided much impetus for this research. In addition, archaeological investigations carried out soon after the Second World War in Algeria (Gaucher 1947), Italy (Selli 1962), Libya (McBurney and Hey 1955) and Spain (Gigout 1959) resulted in the recovery of large numbers of Palaeolithic stone tools from Pleistocene fluvial deposits. These early examples of what has now become more widely known as ‘geoarchaeology’ (Davidson and Shackley 1976; Butzer 1977) or ‘alluvial archaeology’ (Macklin and Needham 1992) were, with their strong interdisciplinary focus, highly innovative and ahead of their time in the way they integrated archaeology, geomorphology, and geochronology. Building on this theme, the principal aim of this chapter is to consider how river systems in the Mediterranean region have responded to the environmental changes that took place during the Late Quaternary–a time interval corresponding approximately to the last 130,000 years. There are a number of reasons for choosing this period for reviewing river-environment interactions in the Mediterranean: 1. It encompasses the last glacial–interglacial cycle (c.130 to 10 ka) for which there is now abundant global evidence from polar ice cores, speleothem records, and lake and marine sediments, for both longand short-term changes in climate. These changes included massive reorganizations of the atmosphere-ocean-cryosphere systems—often over timescales of less than 100 years (Lowe and Walker 1997)—and they are clearly recorded in the Mediterranean region (see Allen et al. 1999 and Chapter 4).

The fluvial record of climate change

“…These records mirror the pattern of stadials and interstadials evident in the Greenland ice core records. What these and other records from both the western [60] and eastern [61] [56]. The proxy climate records (d 18 O from Greenland and arboreal pollen % from Ioannina [57]) are also shown for the same period.…”

“…The proxy climate records (d 18 O from Greenland and arboreal pollen % from Ioannina [57]) are also shown for the same period. The catchments are shown by latitude from north to south, and all sources are given in Macklin & Woodward [56] or cited in the text. Many Mediterranean catchments with headwaters above 2200 m saw the development of glaciers during the cold stages of the Pleistocene; the presence of large ice masses would have exerted a strong influence on runoff and sediment delivery.…”

Environmental evolution and mid–late Holocene climate events in the Valencia lagoon (Mediterranean coast of Spain)

“…Specifically, in the Mediterranean basin extreme hydrological events have been found to be an inherent component of past (Holocene) and present hydrology. For this reason, an important part of palaeoenvironmental Holocene research has focused on identifying phases of high frequency and magnitude of floods related with climatic variability (Benito et al, 2008, 2015; Macklin and Woodward, 2009; Macklin et al, 2006; Thorndycraft and Benito, 2006a, 2006b). In the Mediterranean basin, several research works document a centennial to multicentennial see-saw pattern in flooding, indicating bipolar hydroclimatic conditions during the Holocene.…”

Stochastic alluvial fan and terrace formation triggered by a high-magnitude Holocene landslide in the Klados Gorge, Crete

“…Similar conclusions were drawn by Wegmann (2008) and Macklin (2010), who found that active fan aggradation on Crete generally occurred during glacial stages. These examples illustrate that fan sedimentation occurred more or less in concert with Quaternary climate variability across western and southern Crete, similar to elsewhere in the Mediterranean (Benito et al, 2015;Macklin and Woodward, 2009;Thorndycraft and Benito, 2006;Zielhofer et al, 2008).…”