The Flash Flood pilot basins network (FF network) is built upon a number of existing cooperative structures, linking together hydrometeorological monitoring services, operational forecasting centres and research centres.
These four pilot areas are characterised by a good density of hydrometeorological stations and by good and reliable weather radar coverage. All these observatories are already operational, and incorporate considerable detailed information about flash floods observed in the last decade.
The objective of the FF network is to develop a data-collection strategy that combines collection of conventional hydrometeorological data (with careful analysis of radar observations) and the acquisition of complementary information from field surveys carried out during the days following the event. The observational resources represented by the FF network allow the provision of a coherent database of flash flood events for a variety of hydroclimatic regions across Europe.
|How will the study benefit the people in these areas?
The outcome of this study should improve the effectiveness and efficiency of forecasting, warning, response and preparedness actions. Each pilot area will have a procedural model of these actions, identifying major physical, organisational and institutional structures and their responses to flash flood forecasts.
The Cévennes-Vivarais HO covers an area of 160 x 200 km2 in the south-eastern part of the French Massif Central. Many villages and several small to medium-sized towns exist in the region. The main city, Nîmes, has a population of 200 thousand.
The area is subject to particularly severe flash flood events. The topography of the area ranges from sea level in the south to a maximum height of 1699 m above sea level at Mount Lozère. The main Cévennes rivers (Cance, Doux, Eyrieux, Ardèche, Cèze, Gard and Vidourle) are right bank tributaries of the Rhône river with a typical Mediterranean hydrological regime (i.e. very low water levels during the summer with floods occurring mainly during the autumn). They are characterised by steep slopes in the head tributaries of the Cévennes Mountains.
In terms of geology, the mountainous part of the region (generally in the north-west of the pilot area) corresponds to the Primary era formations of the Massif Central (granite, schists), while sedimentary and detrital formations dominate in the Rhône valley region (south-eastern part of the pilot area) with, in places, karstified limestone.
The North-Eastern Italy HO covers the region formed by the Adige river basin and the Tagliamento river basin.
The Adige River is the second longest river in Italy, 360 km long, rising in the Tyrolean Alps of Northern Italy. It flows south, past Bolzano, Trento, and Verona, to the Po valley where it turns east to flow into the Adriatic Sea. The study is focused on the mountainous part of the basin (12000 km2), which includes two distinct administrative areas: Provincia Autonoma di Bolzano (almost 7000 km2) and Provincia Autonoma di Trento (5000 km2). Altitudes range from 100 m above sea level up to 4000 m above sea level. The region is located south of the inner alpine province: some parts have a dry climate (with a rainfall of 600 mm/year, due to the dual sheltering effect of the mountain range to both the north and the south) and others have a wet climate (with a rainfall of 2500 mm/year) along the Venetian plains. The southern range experiences showery precipitation with thunderstorms and hail, particularly in summer and autumn.
The Tagliamento River (with an area of 2871 km2) is the dominant river system of the Friuli region in north-eastern Italy. From north to south, the Tagliamento River crosses four major regions: (i) the Julian and Carnian Alps, (ii) prealps, (iii) the upper and lower Friulian plain, and (iv) the coast. This steep environmental gradient (north to south) is associated with climatic differences, e.g., annual precipitation ranges from 3100 to 1000 mm/year and mean annual temperature ranges from 5 to 14°C. The southern fringe of the Carnian and Julian Alps frequently receives very intensive rain storms, resulting in severe erosion, especially in the alpine area. The alpine area of Friuli mainly consists of limestone, with a spatial sequence of Silurian, Devonian, Triassic, Jurassic and Cretaceous formations north to south. The basin is characterised by steep slopes and lies in one of the wettest regions of Italy, where annual precipitation can reach 3000 mm. Rainfall is concentrated mainly in heavy and erosive showers determining the torrential regime of the river. Furthermore, the mountain basin is seismically active and has a dense distribution of landslides, resulting in signfiicant bed load and a braided nature of the river downstream. At Pioverno (where the river has an upstream catchment of 2400 km2), the 10 and 100 year return period floods are estimated to be 2150 m3/s and 4300 m3/s, respectively.
|The North-Eastern Italy Pilot Area.
The region of Catalunya is located in the North-East of the Iberian Peninsula and covers an area of 32000 km2.
The pilot area has an increasing altitude from the sea to the inner regions. There are three main mountain ranges. The first two are parallel to the coast (rising up to 500 and 1700 m above sea level), and are located inside a strip of terrain less than 40 km from the sea. These mountains act as a barrier that induces the convection of humid air coming from the sea, favouring the generation and growth of precipitation. The third mountain chain (the Pyrenees) is located to the North, and has the highest elevations of the region (up to 3400 m). The mean annual rainfall over the region is about 600 mm. However, one third of the annual precipitation can usually fall in less than 48 hours. On average, two events exceeding 100 mm/day are recorded every year and the return period for events over 200 mm/day in Catalunya is only two years.
This region is drained by a set of coastal rivers. Many of them cross densely urbanised and industrialised zones. Among them, the Besòs River and the Llobregat River pass north and south, respectively, of the conurbation of Barcelona (with more than 3 millions of inhabitants).
This area is the most vulnerable of the pilot areas from the socio-economical point of view. It is also the best covered by the current radar network.
The Ardennes is an undulating area of moderate relief (maximum elevation of approximately 700 m) and an important natural laboratory to study the hydrometeorology of mountainous catchments. The western part of the Ardennes (France, Belgium, Netherlands) mainly drains to the river Meuse, whereas the eastern part of the region (Luxemburg, Germany) mainly drains to the river Rhine (via the Mosel). Both the Meuse and the Rhine fulfill important functions in the water supply of The Netherlands. These rivers supply water for domestic, industrial and agricultural use and also fulfill important navigational, ecological and recreational functions. It is therefore of significant societal relevance to develop strategies to mitigate the impact of floods and droughts associated with the flow regimes of the rivers Meuse and Rhine. To achieve this objective, the hydrometeorology of the (mostly mountainous) upstream areas, such as the Ardennes, needs to be better understood.
The aim of a recently established research collaboration between Wageningen University (WU), the Royal Meteorological Institute of Belgium (RMI) and the Hydrological Service of the Walloon Region of Belgium (MET-SETHY) is to investigate whether an improved assessment of the space-time structure of precipitation, as can be obtained with a newly installed weather radar in the Ardennes, in combination with an innovative approach towards modelling the rainfall-runoff process, will lead to an improved understanding of the hydrometeorology of Ardennes catchments.
|The Ardennes Pilot Area
Further details of this study can be found here.