No abstract

The effects of the topographic data source and resolution on the hydraulic modelling of floods were analysed. Seven digital terrain models (DTMs) were generated from three different altimetric sources: a global positioning system (GPS) survey and bathymetry; highresolution laser altimetry data LiDAR (light detection and ranging); and vectorial cartography (1:5000). Hydraulic results were obtained, using the HEC-RAS one-dimensional model, for all seven DTMs. The importance of the DTM's accuracy on the hydraulic modelling results was analysed within three different hydraulic contexts: (1) the discharge and water surface elevation results from the hydraulic model; (2)

No abstract

Palaeoflood chronologies from seven Spanish river basins and floodplain aggradation chronologies from thirteen rivers are analysed. These fluvial records were divided in to two sub-sets, namely Atlantic (10 ka record) and Mediterranean (3 ka record) river basins, which represent distinct modern hydroclimatic conditions. In Atlantic basins floods result from intense, widespread rainfalls associated with Atlantic frontal systems transported by westerly airflow. Mediterranean river flooding is related to heavy rainfall induced by mesoscale convective systems (MCSs) during autumn months. Evidence from radiocarbon dates in slackwater flood deposits shows six periods of flood clusters at 10,750-10,240; 9550-9130; 4820-4440; 2865-2350; 960-790; and 520-290 cal BP. Despite the different flood-producing weather conditions in Atlantic and Mediterranean rivers, the radiocarbon sample clusters overlap and indicate changes in largescale atmospheric circulation and climatic conditions in the Iberian Peninsula. Comparison with proxy records of mean temperature for the Northern Hemisphere demonstrates a relationship between the period of slackwater flood deposition and cold climatic phases (e.g. the 2650 yr BP climatic event or AD 1590-1650 period of the Little Ice Age). Radiocarbon dates from aggraded floodplain sediments were clustered at 2710-2320, 2000-1830, and 910-500 cal BP. The first cluster period is in phase with the timing of slackwater deposition, whereas the third (910-500 cal BP) occurs in between two periods of increased flood frequency as indicated by the palaeoflood and documentary flood records. It is argued that the 910-500 cal BP floodplain aggradation period reflects the first post-Roman evidence of environmental change related to generalised land-use changes at the catchment scale, which produced high sediment load transported to overbank areas during high flows.

No abstract

The Anthropocene is proposed as a new interval of geological time in which human influence on Earth and its geological record dominates over natural processes. A major challenge in demarcating the Anthropocene is that the balance between human-influenced and natural processes varies over spatial and temporal scales owing to the inherent variability of both human activities (as associated with culture and modes of development) and natural drivers (e.g. tectonic activity and sea level variation). Against this backdrop, we consider how geomorphology might contribute towards the Anthropocene debate by focusing on human impact on aeolian, fluvial, cryospheric and coastal process domains, and how evidence of this impact is preserved in landforms and sedimentary records. We also consider the evidence for an explicitly anthropogenic geomorphology that includes artificial slopes and other human-created landforms. This provides the basis for discussing the theoretical and practical contributions that geomorphology can make to defining an Anthropocene stratigraphy. It is clear that the relevance of the Anthropocene concept varies considerably amongst different branches of geomorphology, depending on the history of human actions in different process domains. For example, evidence of human dominance is more widespread in fluvial and coastal records than in aeolian and cryospheric records, so geomorphologically the Anthropocene would inevitably comprise a highly diachronous lower boundary. Even to identify this lower boundary, research would need to focus on the disambiguation of human effects on geomorphological and sedimentological signatures. This would require robust data, derived from a combination of modelling and new empirical work rather than an arbitrary ?war of possible boundaries' associated with convenient, but disputed, ?golden? spikes. Rather than being drawn into stratigraphical debates, the primary concern of geomorphology should be with the investigation of processes and landform development, so providing the underpinning science for the study of this time of critical geological transition. Copyright ? 2016 John Wiley & Sons, Ltd.authorsversionPeer reviewe

No 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