A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale.

Climate change has led to concerns about increasing river floods resulting from the greater water-holding capacity of a warmer atmosphere 1 . These concerns are reinforced by evidence of increasing economic losses associated with flooding in many parts of the world, including Europe 2 . Any changes in river floods would have lasting implications for the design of flood protection measures and flood risk zoning. However, existing studies have been unable to identify a consistent continental-scale climatic-change signal in flood discharge observations in Europe 3 , because of the limited spatial coverage and number of hydrometric stations. Here we demonstrate clear regional patterns of both increases and decreases in observed river flood discharges in the past five decades in Europe, which are manifestations of a changing climate. Our results-arising from the most complete database of European flooding so farsuggest that: increasing autumn and winter rainfall has resulted in increasing floods in northwestern Europe; decreasing precipitation and increasing evaporation have led to decreasing floods in medium and large catchments in southern Europe; and decreasing snow cover and snowmelt, resulting from warmer temperatures, have led to decreasing floods in eastern Europe. Regional flood discharge trends in Europe range from an increase of about 11 per cent per decade to a decrease of 23 per cent. Notwithstanding the spatial and temporal heterogeneity of the observational record, the flood changes identified here are broadly consistent with climate model projections for the next century 4,5 , suggesting that climatedriven changes are already happening and supporting calls for the consideration of climate change in flood risk management.River floods are among the most costly natural hazards. Global annual average losses are estimated at US$104 billion 6 and are expected to increase with economic growth, urbanization and climatic change 2,7 . Physical arguments of increased heavy precipitation resulting from the enhanced water-holding capacity of a warmer atmosphere and

This article has been examined maximum runoff of the rivers of the Crimean Mountains. The rivers flow through the western and eastern part of the northern slope Crimean Mountains, and on its southern coast. The largest of them: Belbek, Alma, Salgir, Su-Indol and others. To characterize the maximum runoff of rain floods (the layers of rain floods and maximum discharge of water) on the rivers of the Crimean Mountains were used materials of observations for long-term period (from the beginning of observations to 2010 inclusive) on 54 of streamflow station with using a the so-called «operator» model for maximum runoff formation.

Numerous regional approaches to calculating maximal water discharges have led to their classifica tion (separately for rain floods and spring floods) pre sented in [7]. The formulas for maximal spring flood runoff, in their turn, are divided into two groups:(1) reduction formulas, explicitly reflecting the reduction of unit area spring flood discharges with increasing watershed size;(2) volumetric formulas, expressing the maximal water discharge as a function of the flood volume, its duration, and geometric shape.By their structure and content, maximal runoff formulas for rain floods are divide into four groups:(1) based on the maximal rainfall rate over the design travel time τ;(2) reduction structures;(3) calculation methods based on hydromechanical theories;(4) volumetric formulas.In the general form, the formula of limiting inten sity can be written as:(1)where are ordinates of reduction curve of mean precipitation intensity over the design time τ, H d is the daily maximum of rain, η is an overall runoff coeffi cient.The formulas relying on hydromechanical theories of storm runoff are based on equations of dynamic equilibrium and continuity of runoff for elementary areas or on models of channel isochrones (for watersheds of any size). In the general form, A.N. Befani [1] derived the following basic equation:(2)where ω is the cross section of an open flow, ω f is the cross section of a floodplain flow, ω а is cross section in alluvium, δ is the free porosity of alluvium.With some simplifications, such as assuming a lin ear relationship between ω, on the one hand, and ω f and ω а , on the other hand, integration of (2) yielded a generalized structure of the calculation formulawhere Y m is runoff depth, t c is channel travel time, ϕ is a coefficient of completeness of slope inflow, contrib uting to the formation of q m ; at t d < T 0 ,T 0 is the duration of water inflow from slopes into channel network, k h is hydrographic coefficient; at t c < T 0 ,d 0 ' ; t t q dt ϕ = 1.0, = ∫ ∫ h c h m 0 0 ' , ' t t t t t q B dt k B q dt WATER RESOURCES AND THE REGIME OF WATER BODIES Abstract-Scientific and methodological approaches to calculating characteristics of maximal runoff in Ukrainian rivers are considered.

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