46Scots pine forests subjected to continental Mediterranean climates undergo cold winter 47 temperatures and drought stress. Recent climatic trends towards warmer and drier 48 conditions across the Mediterranean Basin might render some of these pine populations 49 more vulnerable to drought-induced growth decline at the southernmost limit of the 50 species distribution. We investigated how cold winters and dry growing seasons drive 51 the radial growth of Scots pine subject to continental Mediterranean climates by relating 52 growth to climate variables at local (elevational gradient) and regional (latitudinal 53 gradient) scales. Local climate-growth relationships were quantified on different time 54 scales (5-, 10-and 15-days) to evaluate the relative role of elevation and specific site 55 characteristics. A negative water balance driven by high maximum temperatures in June 56 (low-elevation sites) and July (high-elevation sites) was the major constraint on growth, 57 particularly on a 5-to 10-day time scale. Warm nocturnal conditions in January were 58 associated with wider rings at the high-elevation sites. At the regional scale, Scots pine 59 growth mainly responded positively to July precipitation, with a stronger association at 60 lower elevations and higher latitudes. January minimum temperatures showed similar 61 patterns but played a secondary role as a driver of tree growth. The balance between 62 positive and negative effects of summer precipitation and winter temperature on radial 63 growth depends on elevation and latitude, with low-elevation populations being more 64 prone to suffer drought and heat stress, whereas high-elevation populations may be 65 favoured by warmer winter conditions. This negative impact of summer heat and 66 drought has increased during the past decades. This interaction between climate and site 67 conditions and local adaptations is therefore decisive for the future performance and 68 persistence of Scots pine populations in continental Mediterranean climates.

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

Abstract:There is still wide uncertainty about past flash-flood processes in mountain regions owing to the lack of systematic databases on former events. This paper presents a methodology to reconstruct peak discharge of flash floods and illustrates a case in an ungauged catchment in the Spanish Central System. The use of dendrogeomorphic evidence (i.e. scars on trees) together with the combined use of a two-dimensional (2D) numerical hydraulic model and a terrestrial laser scan (TLS) has allowed estimation of peak discharge of a recent flash flood. The size and height distribution of scars observed in the field have been used to define three hypothetical scenarios (S min or minimum scenario; S med or medium scenario; and S max or maximum scenario), thus illustrating the uncertainty involved in peak-discharge estimation of flash floods in ungauged torrents.All scars analysed with dendrogeomorphic techniques stem from a large flash flood which took place on 17 December 1997. On the basis of the scenarios, peak discharge is estimated to 79 š 14 m 3 s 1 . The average deviation obtained between flood stage and expected scar height was 0Ð09 š 0Ð53 m. From the data, it becomes obvious that the geomorphic position of trees is the main factor controlling deviation rate. In this sense, scars with minimum deviation were located on trees growing in exposed locations, especially on unruffled bedrock where the model predicts higher specific kinetic energy. The approach used in this study demonstrates the potential of tree-ring analysis in palaeohydrology and for flood-risk assessment in catchments with vulnerable goods and infrastructure.