Giovanni Battista Chirico

Changing climate shifts timing of European floods

Flooding along the river Will a warming climate affect river floods? The prevailing sentiment is yes, but a consistent signal in flood magnitudes has not been found. Blöschl et al. analyzed the timing of river floods in Europe over the past 50 years and found clear patterns of changes in flood timing that can be ascribed to climate effects (see the Perspective by Slater and Wilby). These variations include earlier spring snowmelt floods in northeastern Europe, later winter floods around the North Sea and parts of the Mediterranean coast owing to delayed winter storms, and earlier winter floods in western Europe caused by earlier soil moisture maxima. Science, this issue p. 588 see also p. 552 Climate change is affecting the timing of river flooding across Europe. 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.

Regime shift by an exotic nitrogen-fixing shrub mediates plant facilitation in primary succession.

Ecosystem invasion by non-native, nitrogen-fixing species is a global phenomenon with serious ecological consequences. However, in the Mediterranean basin few studies addressed the impact of invasion by nitrogen-fixing shrubs on soil quality and hydrological properties at local scale, and the possible effects on succession dynamics and ecosystem invasibility by further species. In this multidisciplinary study we investigated the impact of Genista aetnensis (Biv.) DC., an exotic nitrogen-fixing shrub, on the Vesuvius Grand Cone (Southern Italy). Specifically, we tested the hypotheses that the invasion of G. aetnensis has a significant impact on soil quality, soil hydrological regime, local microclimate and plant community structure, and that its impact increases during the plant ontogenetic cycle. We showed that G. aetnensis, in a relatively short time-span (i.e. ~ 40 years), has been able to build-up an island of fertility under its canopy, by accumulating considerable stocks of C, N, and P in the soil, and by also improving the soil hydrological properties. Moreover, G. aetnensis mitigates the daily range of soil temperature, reducing the exposure of coexisting plants to extremely high temperatures and water loss by soil evaporation, particularly during the growing season. Such amelioration of soil quality, coupled with the mitigation of below-canopy microclimatic conditions, has enhanced plant colonization of the barren Grand Cone slopes, by both herbaceous and woody species. These results suggest that the invasion of G. aetnensis could eventually drive to the spread of other, more resource-demanding exotic species, promoting alternative successional trajectories that may dramatically affect the local landscape. Our study is the first record of the invasion of G. aetnensis, an additional example of the regime shifts driven by N-fixing shrubs in Mediterranean region. Further studies are needed to identity specific management practices that can limit the spread and impacts of this species.

The role of terrain analysis in using and developing pedotransfer functions

Publisher Summary This chapter discusses the way terrain features can be employed to efficiently parameterize the soil hydraulic behavior in land-surface models via pedotransfer functions (PTFs) and to improve the prediction performance of PTFs at various scales. The problems of better assessing the spatial variability of soil hydraulic properties and improving in the local estimation of these properties can be translated into two main issues: more efficient interpolations among available input predictor variables and the possibility to locally calibrate a PTF in a cost-effective way. Therefore, the chapter presents a framework in which terrain attributes can help resolve both these issues when a PTF is employed to estimate soil hydraulic properties. The chapter illustrates the techniques developed for computing terrain attributes and discusses the issue of interpolating spatially sparse data of soil properties using terrain attributes as ancillary data. The chapter also discusses the opportunities in the improvement of predictive capabilities of PTFs via incorporation of topographic information.

Flash flood occurrence and magnitude assessment in an alluvial fan context: the October 2011 event in the Southern Apennines

This study presents the analysis of flash floods triggered by an extreme rainfall event that occurred on 7 October, 2011, over the Marzano carbonate massif (Southern Apennines). The rainfall event reactivated alluvial fans built up at the outlet of two mountain basins. Detailed geological surveys carried out immediately after the event allowed the reconstruction of the main erosion and depositional processes that occurred both in the drainage basin and in the fan areas. The volume of materials eroded in the basin and deposited in the fan was evaluated by means of accurate topographic surveying and GPS measurements. Morphological and morphometric properties of the basin/fan system as well as the presence of human interventions and structures along the main channel and in the fan area influenced flow propagation. The transported materials came mainly from debris and gravels previously accumulated along the stream beds and mobilised by the flow during the event. No significant evidence of landslide contribution to transported bed load was detected. Extensive damage was done to buildings, river bank structures and agricultural crops. Despite the existence of hundreds of similar alluvial/fan systems in the Southern Apennines, few studies have been conducted to support adequate risk mitigation action in these areas. Indeed, to our knowledge, this is the first study focusing on assessing the magnitude of alluvial fan flooding in the context of the Southern Apennines. Studies like the present one may help determine the volumes involved during flash floods whilst providing support for detailed flood hazard zoning and for risk mitigation planning.

Functional evaluation of a simplified scaling method for assessing the spatial variability of soil hydraulic properties at the hillslope scale

Abstract Mapping soil hydraulic parameters with traditional scaling methods that use laboratory-determined hydraulic characteristics (the LAB method) is not always feasible as it involves expensive, time-consuming and sophisticated measurements on soil samples collected in several locations of the study area. An alternative scaling method (the AP method) has been recently proposed to indirectly retrieve the soil hydraulic properties following the Arya-Paris physico-empirical pedotransfer function, which makes use of particle-size distribution and bulk density values. In this synthetic study we verify the performance of the AP method from a functional perspective, by evaluating the differences in the simulated soil water budget through a Monte Carlo approach. Notwithstanding that the AP method can provide soil hydraulic property patterns with faster experimental procedures and minor costs, we observe significant bias in the predicted spatially-averaged soil water budget due to a poor parametric calibration of the AP method and an imprecise identification of the spatial correlation structure of the AP-estimated scaling factors. Citation Nasta, P., Romano, N., and Chirico, G.B., 2013. Functional evaluation of a simplified scaling method for assessing the spatial variability of soil hydraulic properties at the hillslope scale. Hydrological Sciences Journal, 58 (5), 1059–1071.

Impact of mountain permafrost on flow path and runoff response in a high alpine catchment

Permafrost in high alpine catchments is expected to disappear in future warmer climates, but the hydrological impact of such changes is poorly understood. This paper investigates the flow paths and the hydrological response in a 5 km2 high alpine catchment in the Otztal Alps, Austria, and their changes resulting from a loss of permafrost. Spatial permafrost distribution, depth to the permafrost table and depth to the bedrock were mapped by geophysical methods. Catchment runoff and meteorological variables were monitored from June 2008 to December 2011. These data were used along with field experience to infer conceptual schemes of the dominant flow paths in four types of hillslopes that differ in terms of their unconsolidated sediment characteristics and the presence of permafrost. The four types are: talus fans, rock glaciers, Little Ice Age (LIA) till and Pre-LIA till. Permafrost tends to occur in the first three types, but is absent from Pre-LIA till. Based on these flow path concepts, runoff was simulated for present conditions and for future conditions when permafrost has completely disappeared. The simulations indicate that complete disappearance of permafrost will reduce flood peaks by up to 17% and increase runoff during recession by up to 19%. It is argued that change modeling needs to account for flow path types and their changes based on geophysical surveys and field investigations. This article is protected by copyright. All rights reserved.

Adaptive Kalman Filtering for Postprocessing Ensemble Numerical Weather Predictions

AbstractForecasts from numerical weather prediction models suffer from systematic and nonsystematic errors, which originate from various sources such as subgrid-scale variability affecting large scales. Statistical postprocessing techniques can partly remove such errors. Adaptive MOS techniques based on Kalman filters (here called AMOS), are used to sequentially postprocess the forecasts, by continuously updating the correction parameters as new ground observations become available. These techniques, originally proposed for deterministic forecasts, are valuable when long training datasets do not exist. Here, a new adaptive postprocessing technique for ensemble predictions (called AEMOS) is introduced. The proposed method implements a Kalman filtering approach that fully exploits the information content of the ensemble for updating the parameters of the postprocessing equation. A verification study for the region of Campania in southern Italy is performed. Two years (2014–15) of daily meteorological observ...

How deep can forest vegetation cover extend their hydrological reinforcing contribution

University of Tehran, Department of Forestry and Forest Economics, Karaj, Iran University of Tehran, Department of Range and Watershed Management, Karaj, Iran University of Minnesota, Department of Bioproducts and Biosystems Engineering, St. Paul, Minnesota, USA University of Napoli Federico II, Department of Agriculture, Division of Agricultural, Forest and Biosystems Engineering, Naples, Italy Correspondence Ehsan Abdi, Department of Forestry and Forest Economics, University of Tehran, Karaj, Tehran 3158777871, Iran. Email: abdie@ut.ac.ir

Soil water dynamics under different forest vegetation cover: Implications for hillslope stability: Soil water dynamics under forest vegetation cover

Though it is well known that vegetation affects the water balance of soils through canopy interception and evapotranspiration, its hydrological contribution to soil hydrology and stability is yet to be fully quantified. To improve understanding of this hydrological process, soil water dynamics have been monitored at three adjacent hillslopes with different vegetation covers (deciduous tree cover, coniferous tree cover, and grass cover), for nine months from December 2014 to September 2015. The monitored soil moisture values were translated into soil matric suction (SMS) values to facilitate the analysis of hillslope stability. Our observations showed significant seasonal variations in SMS for each vegetation cover condition. However, a significant difference between different vegetation covers was only evident during the winter season where the mean SMS under coniferous tree cover (83.6 kPa) was significantly greater than that under grass cover (41 kPa). The hydrological reinforcing contribution due to matric suction was highest for the hillslope with coniferous tree cover, while the hillslope with deciduous tree cover was second and the hillslope with grass cover was third. The greatest contributions for all cover types were during the summer season. During the winter season, the wettest period of the monitoring study, the additional hydrological reinforcing contributions provided by the deciduous tree cover (1.5 to 6.5 kPa) or the grass cover (0.9 to 5.4 kPa) were insufficient to avoid potential slope failure conditions. However, the additional hydrological reinforcing contribution from the coniferous tree cover (5.8 to 10.4 kPa) was sufficient to provide potentially stable hillslope conditions during the winter season. Our study clearly suggests that during the winter season the hydrological effects from both deciduous tree and grass covers are insufficient to promote slope stability, while the hydrological reinforcing effects from the coniferous tree cover are sufficient even during the winter season. Copyright

Quantitative Interpretation of Time-lapse MALM Measurements During a Saline Tracer Injection in an Alluvial Aquifer

This study presents the results of a saline tracer test conducted on an unconfined alluvial aquifer placed in the Alento River Valley (Campania region, South-Western Italy) and monitored by Mise-a-la-Masse measurements. The aim of this test is the investigation of groundwater flow field by a time-lapse analysis. The work first introduces the local hydrogeology of the investigated system and the experimental set-up. The results of the geophysical tracer test are then described and followed by the discussion of several simulations conducted on a 3D electrical model of the system. Finally, the comparison between real and simulated datasets is discussed in order to highlight advantages and limitations of Mise-a-la Masse technique when applied for hydrogeological purposes.