Centre de Recherche en Géographie

Abstract Risk management has reduced vulnerability to floods and droughts globally 1,2 , yet their impacts are still increasing 3 . An improved understanding of the causes of changing impacts is therefore needed, but has been hampered by a lack of empirical data 4,5 . On the basis of a global dataset of 45 pairs of events that occurred within the same area, we show that risk management generally reduces the impacts of floods and droughts but faces difficulties in reducing the impacts of unprecedented events of a magnitude not previously experienced. If the second event was much more hazardous than the first, its impact was almost always higher. This is because management was not designed to deal with such extreme events: for example, they exceeded the design levels of levees and reservoirs. In two success stories, the impact of the second, more hazardous, event was lower, as a result of improved risk management governance and high investment in integrated management. The observed difficulty of managing unprecedented events is alarming, given that more extreme hydrological events are projected owing to climate change 3 .

Abstract. Strong winds may uproot and break trees and represent a major natural disturbance for European forests. Wind disturbances have intensified over the last decades globally and are expected to further rise in view of the effects of climate change. Despite the importance of such natural disturbances, there are currently no spatially explicit databases of wind-related impact at a pan-European scale. Here, we present a new database of wind disturbances in European forests (FORWIND). FORWIND is comprised of more than 80 000 spatially delineated areas in Europe that were disturbed by wind in the period 2000–2018 and describes them in a harmonized and consistent geographical vector format. The database includes all major windstorms that occurred over the observational period (e.g. Gudrun, Kyrill, Klaus, Xynthia and Vaia) and represents approximately 30 % of the reported damaging wind events in Europe. Correlation analyses between the areas in FORWIND and land cover changes retrieved from the Landsat-based Global Forest Change dataset and the MODIS Global Disturbance Index corroborate the robustness of FORWIND. Spearman rank coefficients range between 0.27 and 0.48 (p value < 0.05). When recorded forest areas are rescaled based on their damage degree, correlation increases to 0.54. Wind-damaged growing stock volumes reported in national inventories (FORESTORM dataset) are generally higher than analogous metrics provided by FORWIND in combination with satellite-based biomass and country-scale statistics of growing stock volume. The potential of FORWIND is explored for a range of challenging topics and scientific fields, including scaling relations of wind damage, forest vulnerability modelling, remote sensing monitoring of forest disturbance, representation of uprooting and breakage of trees in large-scale land surface models, and hydrogeological risks following wind damage. Overall, FORWIND represents an essential and open-access spatial source that can be used to improve the understanding, detection and prediction of wind disturbances and the consequent impacts on forest ecosystems and the land–atmosphere system. Data sharing is encouraged in order to continuously update and improve FORWIND. The dataset is available at https://doi.org/10.6084/m9.figshare.9555008 (Forzieri et al., 2019).

Abstract. Streamflow is often the only variable used to evaluate hydrological models. In a previous international comparison study, eight research groups followed an identical protocol to calibrate 12 hydrological models using observed streamflow of catchments within the Meuse basin. In the current study, we quantify the differences in five states and fluxes of these 12 process-based models with similar streamflow performance, in a systematic and comprehensive way. Next, we assess model behavior plausibility by ranking the models for a set of criteria using streamflow and remote-sensing data of evaporation, snow cover, soil moisture and total storage anomalies. We found substantial dissimilarities between models for annual interception and seasonal evaporation rates, the annual number of days with water stored as snow, the mean annual maximum snow storage and the size of the root-zone storage capacity. These differences in internal process representation imply that these models cannot all simultaneously be close to reality. Modeled annual evaporation rates are consistent with Global Land Evaporation Amsterdam Model (GLEAM) estimates. However, there is a large uncertainty in modeled and remote-sensing annual interception. Substantial differences are also found between Moderate Resolution Imaging Spectroradiometer (MODIS) and modeled number of days with snow storage. Models with relatively small root-zone storage capacities and without root water uptake reduction under dry conditions tend to have an empty root-zone storage for several days each summer, while this is not suggested by remote-sensing data of evaporation, soil moisture and vegetation indices. On the other hand, models with relatively large root-zone storage capacities tend to overestimate very dry total storage anomalies of the Gravity Recovery and Climate Experiment (GRACE). None of the models is systematically consistent with the information available from all different (remote-sensing) data sources. Yet we did not reject models given the uncertainties in these data sources and their changing relevance for the system under investigation.

Abstract. International collaboration between research institutes and universities is a promising way to reach consensus on hydrological model development. Although model comparison studies are very valuable for international cooperation, they do often not lead to very clear new insights regarding the relevance of the modelled processes. We hypothesise that this is partly caused by model complexity and the comparison methods used, which focus too much on a good overall performance instead of focusing on a variety of specific events. In this study, we use an approach that focuses on the evaluation of specific events and characteristics. Eight international research groups calibrated their hourly model on the Ourthe catchment in Belgium and carried out a validation in time for the Ourthe catchment and a validation in space for nested and neighbouring catchments. The same protocol was followed for each model and an ensemble of best-performing parameter sets was selected. Although the models showed similar performances based on general metrics (i.e. the Nash–Sutcliffe efficiency), clear differences could be observed for specific events. We analysed the hydrographs of these specific events and conducted three types of statistical analyses on the entire time series: cumulative discharges, empirical extreme value distribution of the peak flows and flow duration curves for low flows. The results illustrate the relevance of including a very quick flow reservoir preceding the root zone storage to model peaks during low flows and including a slow reservoir in parallel with the fast reservoir to model the recession for the studied catchments. This intercomparison enhanced the understanding of the hydrological functioning of the catchment, in particular for low flows, and enabled to identify present knowledge gaps for other parts of the hydrograph. Above all, it helped to evaluate each model against a set of alternative models.

Abstract. As the adverse impacts of hydrological extremes increase in many regions of the world, a better understanding of the drivers of changes in risk and impacts is essential for effective flood and drought risk management and climate adaptation. However, there is currently a lack of comprehensive, empirical data about the processes, interactions, and feedbacks in complex human–water systems leading to flood and drought impacts. Here we present a benchmark dataset containing socio-hydrological data of paired events, i.e. two floods or two droughts that occurred in the same area. The 45 paired events occurred in 42 different study areas and cover a wide range of socio-economic and hydro-climatic conditions. The dataset is unique in covering both floods and droughts, in the number of cases assessed and in the quantity of socio-hydrological data. The benchmark dataset comprises (1) detailed review-style reports about the events and key processes between the two events of a pair; (2) the key data table containing variables that assess the indicators which characterize management shortcomings, hazard, exposure, vulnerability, and impacts of all events; and (3) a table of the indicators of change that indicate the differences between the first and second event of a pair. The advantages of the dataset are that it enables comparative analyses across all the paired events based on the indicators of change and allows for detailed context- and location-specific assessments based on the extensive data and reports of the individual study areas. The dataset can be used by the scientific community for exploratory data analyses, e.g. focused on causal links between risk management; changes in hazard, exposure and vulnerability; and flood or drought impacts. The data can also be used for the development, calibration, and validation of socio-hydrological models. The dataset is available to the public through the GFZ Data Services (Kreibich et al., 2023, https://doi.org/10.5880/GFZ.4.4.2023.001).

Abstract. Streamflow is often the only variable used to constrain hydrological models. In a previous international comparison study, eight research groups followed an identical protocol to calibrate a total of twelve hydrological models using observed streamflow of catchments within the Meuse basin. In the current study, we hypothesize that these twelve process-based models with similar streamflow performance have similar representations of internal states and fluxes. We test our hypothesis by comparing internal states and fluxes between models and we assess their plausibility using remotely-sensed products of evaporation, snow cover, soil moisture and total storage anomalies. Our results indicate that models with similar streamflow performance represent internal states and fluxes differently. Substantial dissimilarities between models are found for annual and seasonal evaporation and interception rates, the number of days per year with water stored as snow, the mean annual maximum snow storage and the size of the root-zone storage capacity. Relatively small root-zone storage capacities for several models lead to drying-out of the root-zone storage and significant reduction of evaporative fluxes each summer, which is not suggested by remotely-sensed estimates of evaporation and root-zone soil moisture. These differences in internal process representation imply that these models cannot all simultaneously be close to reality. Using remotely-sensed products, we could evaluate the plausibility of model representations only to some extent, as many of these internal variables remain unknown, highlighting the need for experimental research. We also encourage modelers to rely on multi-model and multi-parameter studies to reveal to decision-makers the uncertainties inherent to the heterogeneity of catchments and the lack of evaluation data.

This paper focuses upon the youngest terraces of the M oselle and its tributary the M eurthe ( NE F rance and SW G ermany). It includes research on several sections, in particular the key sections of G olbey‐ P ré D roué and T hörnich‐ H ochrech (located in the vicinity of the V osges M assif and in the R henish M assif, respectively), and the use of the O ptically S timulated L uminescence ( OSL ) dating method. Our investigations made it possible to obtain a more robust chronostratigraphical framework and to update the previous model of fluvial response to climate change. The results demonstrate that the M oselle terrace M 3 (first terrace formed after the capture of the U pper M oselle by the P alaeo‐ M eurthe) has the same age from the V osges to the R henish M assif. The formation of this terrace included two main periods of sedimentation attributed to the L ate S aalian ( MIS 6) and the E arly W eichselian ( MIS 5), respectively. They were separated by a major episode of fluvial erosion that may be allocated to the MIS 6–5 transition on the basis of chronological and sedimentological evidence. This erosion led to the removal of most of the MIS 6 deposits, whereas the MIS 5 deposits have been widely preserved following the subsequent ( MIS 5–4) terrace incision. This evolution somewhat contrasts with that observed in the S arre valley, the main tributary of the M oselle, and with many fluvial systems in western Europe, which show better preservation of deposits from cold periods. This atypical behaviour is explained by the relationship between the fluvial evolution and the glaciers covering the upper M oselle catchment ( V osges M assif) during the P leistocene cold periods.

Abstract Groundwater recharge depends generally on precipitation. In this study, a geographical information system (GIS) procedure was applied to assess the climate change effect on groundwater recharge in the Grand Est region of France. The analysis comprises high‐resolution climate models that reflect the long‐term climatological regime. The hydrological properties include aquifers, land‐cover and terrain morphology data, which were used to develop the potential infiltration map of the study area. Two parameters, the De Martonne aridity index and effective precipitation, were combined into a 5 × 5 matrix to assess the climate change effect on groundwater recharge during the past (1990s), present (2020s) and future (2050s) periods. The present and future intense aridization and the depletion of the effective precipitation (< 650 mm) reveal the negative effects of climate change on aquifers’ recharge in the Grand Est region. The areas with high and very high climate effects will increase in the 2020s and 2050s. These areas extend mainly in the western, north‐central and northeastern parts of the region occupying the Rhine, Aube and Marne valleys. The medium effect could be found in the central, southern and northwestern parts, while the low impact on groundwater recharge was verified in the northwestern and southeastern parts of the region. The area with low effects of climate change extends mostly in the Vosges and Ardennes mountains. These findings contribute to the long‐term hydrogeological studies in the Grand Est region.

The lower Oued Noun valley, in the arid region of the Atlantic SW Anti‑Atlas, contains an extensive Soltanian (= Upper Pleistocene proparte) terrace. The paper presents dates for these deposits and an interpretation of their fluvial dynamic and morpho-climatic geneses in this distal part of the valley. The Soltanian terrace, about 30 m thick at Fort Oued Noun, consists of 3 units: a basal deposit of coarse gravel buried by slope deposits and travertine (Unit 1); a main unit, more than 20 m thick (Unit 2) that consists of at least 7 repeated sequences each comprising basal fine gravels and sands, associated with detrital travertine, overlain by stromatolithic tufa and finally by a thick accumulation of sandy silts. These silts were deposited by suspension and decantation in shallow non‑turbulent water bodies. The gravels, sands and travertines are more prominent at the bottom and in the upper parts of Unit 2 whilst silts dominate the mid members. Middle Paleolithic artefacts and bones of large mammals are found throughout this Unit. Unit 3, at the top of the formation, comprises red silts that differ from those of Unit 2, containing more aeolian grains and more palygorskyte and being spatially associated with adjacent tributaries fans. Radiometric dates were obtained on travertine (U/Th), on quartz grains extracted from sediments (OSL) and on Melanopsis and Charcoal (14C). U/Th results show three travertine constructions at ca 90, 55-50 and 25-20 ka B.P. The 90 ka dates, however, are not in correct stratigraphic position. The OSL dates suggest that the period of silt aggradation of Unit 2 occured between ca. 50 and 25 ka B.P., the main part of them being deposited between 40 and 30 ka B.P. 14C dates from the upper part of Unit 2 and the base of Unit 3, range between ca 28 and 18 ka B.P. These dates, together with geomorphological and sedimentological analyses, indicate that the valley floor had been lowered to its present depth before ca. 90 ka B.P. However, the slope deposits, older travertines and the basal gravel (Unit 1), classic fluvial and colluvial deposits, are not yet securely dated but they possibly correspond with wetter episodes in O.I.S.stages 5b, 5a and 4, or even later. The silts that form the bulk of Unit 2 were deposited into shallow swamps during biostasic episodes of O.I.S. 3 and were associated with high groundwater levels. Then, large mammals found grass and water along the valley and were hunted by Middle Paleolithic people. The water table remained high after 30 ka B.P. and the gravelbed channels of the local tributaries were active during the 30-20 ka B.P. period. After ca. 20 ka, sediments suggest more varied conditions in this part of the valley, vegetation disappeared and soils were reworked into local colluvial fans, with concomitant aeolian deposits (Unit 3, O.I.S. 2). Finally, deep linear incision occured, dissecting the Soltanian aggraded valley floor during the early Holocene.

L'oued Assaka draîne un important bassin versant sur la bordure sud de l'Anti-Atlas occidental et ses marges sahariennes dans la région de Guelmim. Il traverse les derniers chaînons anti-atlasiques plissés avant de déboucher dans l'océan Atlantique. Dans cette partie de son cours, il a édifié un système de terrasses alluviales étagées pour les plus anciennes et emboîtées pour les dernières. L'une d'entre elles est particulièrement remarquable à la fois par sa puissance, la variété de ses dépôts, ainsi que par leur contenu. Les divers faciès sédimentaires visibles grâce à une forte incision linéaire actuelle qui recoupe l'ensemble de la formation permettent de reconstituer les paléoenvironnements, la dynamique passée de l'oued et de proposer une interprétation des dépôts en relation avec l'évolution climatique régionale et globale. Cette séquence sédimentaire paraît avoir enregistré en haute résolution des événements climatiques rapides durant les stades isotopiques 5 à 2. Elle fournit des repères concernant la réponse du continent africain face aux changements climatiques globaux à la frontière des domaines méditerranéen et saharien.

Le patrimoine industriel est l’un des derniers types de patrimoine à être protégé. Cependant, le mouvement de protection est particulièrement précoce au Royaume-Uni, principalement en raison de la profondeur de l’industrialisation de ce pays qui a vu naître l’industrie.Cet article évoque l’image et la diversité de ce patrimoine à travers l’étude de ses paysages et de ses territoires, de la grande à la petite échelle.Il débute par une brève analyse du mouvement, replacé dans un contexte international. Il montre ensuite plusieurs exemples de conservation et/ou de préservation, d’une ruine maintenue en l’état à une zone commerciale réutilisant un ancien site industriel et ses usines. Il insiste ensuite sur l’élargissement des territoires protégés en tant que patrimoine industriel, d’un seul objet industriel placé dans un square pour rappeler l’ancienne gloire industrielle d’une ville, à une vallée entière ou un bassin charbonnier de plusieurs centaines de km², incluant, par exemple, plusieurs villes-usines ou mines. Enfin, cet article traite de la mise en réseau croissante du patrimoine industriel britannique, à différents niveaux : européen et mondial, avec l’inscription d’éléments industriels au patrimoine mondial de l’UNESCO.

Abstract. Besides other non-behavioural factors, low-light conditions significantly influence the frequency of traffic accidents in an urban environment. This paper intends to identify the impact of low-light conditions on traffic accidents in the city of Cluj-Napoca, Romania. The dependence degree between light and the number of traffic accidents was analysed using the Pearson correlation, and the relation between the spatial distribution of traffic accidents and the light conditions was determined by the frequency ratio model. The vulnerable areas within the city were identified based on the calculation of the injury rate for the 0.5 km2 areas uniformly distributed within the study area. The results show a strong linear correlation between the low-light conditions and the number of traffic accidents in terms of three seasonal variations and a high probability of traffic accident occurrence under the above-mentioned conditions at the city entrances/exits, which represent vulnerable areas within the study area. Knowing the linear dependence and the spatial relation between the low light and the number of traffic accidents, as well as the consequences induced by their occurrence, enabled us to identify the areas of high traffic accident risk in Cluj-Napoca.

The sustainability of a territory is closely related to its resources. Due to climate change, the most precious natural resource, water, has been negatively affected by climatic conditions in terms of quantity and quality. CLIMAT datasets of 1 km2 spatial resolution were used and processed in the ArcGIS environment to generate maps of actual evapotranspiration, water availability, and effective precipitation for the periods of 1961–1990 (1990s), 2011–2040 (2020s), and 2041–2070 (2050s). The product is of paramount importance for the analysis of the actual situation in Europe indicating high water availability in the Alps Range, the Carpathians Mountains, Northern European countries, and the British Islands. On the other hand, low water availability has been evidenced in the Southern and Eastern European areas. For the future period (2050s), the monthly potential evapotranspiration is expected to increase by 30%. The climate models also show an increase in the actual evapotranspiration between past and future periods by 40%. The changes in water availability and effective precipitation between the past (1990s) and future (2050s) indicate decreases of 10%. The most affected areas by climate change are located within the Mediterranean areas, the Iberian Peninsula, and Eastern Europe.

Les transitions énergétiques du XX e siècle ont créé un monde constitué de pays à des stades de développement différents, qui se traduisent par des consommations d’énergie primaire par habitant très inégales. La transition des énergies fossiles vers les énergies renouvelables va entraîner de profonds changements géographiques. Mais, pour que ces changements puissent se produire, encore faut-il que soient surmontées de nombreuses contraintes techniques et géographiques qui freinent le développement des énergies renouvelables. Cette transition énergétique ne peut être qu’un processus très long, au fur et à mesure que sera reconfiguré le système énergétique dans les différentes catégories de pays. Classification JEL : Q42, N50, O20

La ville-usine se définit comme une ville entièrement née autour d’une ou plusieurs usines. L’approche par les paysages permet de l’appréhender comme un système, somme d’éléments interactifs directement ou indirectement liés à la production industrielle. Aux côtés de constantes que l’on retrouve dans toutes les villes-usines, les paysages des villes-usines oscillent entre deux types majeurs : un paysage désordonné qui est celui des villes-usines lentement constituées autour de nombreuses usines plutôt petites et un paysage au contraire très ordonné, né autour de grosses usines intégrées, qui est celui des villes-usines géantes et cohérentes particulièrement présentes en Europe de l’Est. Avec la fin de l’activité industrielle, ces paysages désormais hérités n’ont pu être considérés comme dignes d’intérêt qu’après une phase de deuil caractérisée par de nombreuses destructions destinées à tourner la page d’une époque industrielle symbole d’échec. Ainsi, en fonction de l’intensité et de la durée de la phase de deuil, le paysage de la ville-usine a pu être nié et détruit, partiellement ou intégralement protégé. Cette variété de réactions est liée à l’histoire industrielle et politique des territoires, mais surtout au jeu des acteurs, dans un dialogue à trois entre une population de plus en plus favorable à la préservation de la mémoire industrielle, une puissance publique qui a compris l’intérêt identitaire fédérateur de la préservation des paysages industriels hérités, et un secteur privé qui hésite à investir dans un paysage difficile à valoriser.

Dans les régions arides, la datation des travertins conduit à établir une chronologie de périodes humides. Des travertins de cascade, fluviatiles et hydrothermaux ont été échantillonnés à la bordure nord du Sahara marocain et datés par la méthode des isotopes de l’Uranium, à la fois par spectrométrie alpha et spectrométrie de masse (TIMS). Les résultats indiquent que les constructions de travertins se produisent avant le stade isotopique marin (SIM) 11, pendant le SIM 9-8, secondairement durant le SIM 5 et principalement durant le SIM 3 et le SIM 2. La relation entre les travertins et les phases humides se vérifie à l’échelle du Quaternaire. À l’échelle plus détaillée des périodes récentes, les constructions s’effectuent autour de 50, 30 et 15 ka BP, apparemment en relation avec des refroidissements de l’Atlantique subtropical oriental. Mais le dispositif géomorphologique induit dans chaque cas des différences dans la construction travertineuse : réponse plus tardive des tertres hydrothermaux à l’accroissement pluviométrique, aridification plus précoce des travertins fluviatiles. Les travertins des régions arides continentales sont ainsi des dépôts discontinus incluant des réponses climatiques à la fois planétaires et régionales.

Abstract This paper aims to provide a synthesis and update concerning the fluvial terraces of the rivers flowing from the Vosges Massif (Moselle and palaeo Upper-Moselle-Meuse, Meurthe, Sarre). The terraces of these rivers are especially well-developed in the marly depressions of the Eastern Paris Basin, justifying an extensive field mapping expedition. The main rivers exhibit terrace staircases with 8 to 13 stepped terrace steps within 100m of the present valley floor. The fluvial sediments mainly originate from the Vosges Massif (crystalline basement and Permo-Triassic sandstones and conglomerates). Another peculiarity of the study area is the presence of several palaeovalleys, typically related to fluvial capture events which occurred to the detriment of the River Meuse. Many palaeomeanders have also been recognised in the Paris Basin (Meuse catchment), and the Rhenish Massif (Moselle and Sarre valleys). Despite some similarities, palaeoenvironmental reconstructions provide evidence for the terrace staircases being distinct from one valley / section of valley to another. These differences are related to the morphostructural framework and to the climate forcing (presence/absence of glaciers in the upper catchment of the rivers). The chronological framework suggests that the terrace sequences and the main capture events may be older than previously thought.

International audience

Available data from nearby gauging stations can provide a great source of hydrometric information that is potentially transferable to an ungauged site. Furthermore, streamflow measurements may even be available for the ungauged site. This paper explores the potential of four distance-based regionalization methods to simulate daily hydrographs at almost ungauged pollution-control sites. Two methods use only the hydrological information provided by neighbouring catchments; the other two are new regionalization methods parameterized with a limited number of streamflow data available at the site of interest. Based on a network of 149 streamgauges and 21 pollution-control sites located in the Upper Rhine-Meuse area, the comparative assessment demonstrates the benefit of making available point streamflow measurements at the location of interest for improving quantitative streamflow prediction. The advantage is moderate for the prediction of flow types (stormflow, recession flow, baseflow) and pulse shape (duration of rising limb and falling limb). Editor Z.W. Kundzewicz; Associate editor A. Viglione

A l’heure où plus de 75 % de la population française vit en ville, se pose de plus en plus clairement la question du traitement des espaces urbains en difficulté spatialement (friches, déprise…) ou socialement (délinquance, communautarisme…). Si les seconds, correspondant le plus souvent aux grands ensembles des années 1960, ont la faveur évidente des programmes urbains nationaux, les premiers sont le plus souvent traités au niveau local mais ne demandent pas moins d’investissements politique et financier. C’est le cas à Nancy, où le quartier industrialo-urbain de Meurthe-Canal, né, en périphérie du centre et à la du fin du XIXe siècle, de la concentration d’activités diverses et d’habitat entre la Meurthe et le canal de la Marne au Rhin, se trouve, à la fin du XXe siècle, enclavé dans le tissu urbain et en grande partie en friche. Cette situation mène, à partir du milieu des années 1990, à un ambitieux programme de renouveau urbain encore en cours aujourd’hui et qui, bien plus que de traiter simplement le quartier en question, est aussi une opportunité pour les autorités locales (municipalité et communauté urbaine), de repenser l’organisation spatiale de la ville toute entière.