Accuracy Assessment of Digital Terrain Model Dataset Sources for Hydrogeomorphological Modelling in Small Mediterranean Catchments

Digital terrain models (DTMs) are a fundamental source of information in Earth sciences. DTM-based studies, however, can contain remarkable biases if limitations and inaccuracies in these models are disregarded. In this work, four freely available datasets, including Shuttle Radar Topography Mission C-Band Synthetic Aperture Radar (SRTM C-SAR V3 DEM), Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Map (ASTER GDEM V2), and two nationwide airborne light detection and ranging (LiDAR)-derived DTMs (at 5-m and 1-m spatial resolution, respectively) were analysed in three geomorphologically contrasting, small (3-5 km(2)) catchments located in Mediterranean landscapes under intensive human influence (Mallorca Island, Spain). Vertical accuracy as well as the influence of each dataset's characteristics on hydrological and geomorphological modelling applicability were assessed by using ground-truth data, classic geometric and morphometric parameters, and a recently proposed index of sediment connectivity. Overall vertical accuracyexpressed as the root mean squared error (RMSE) and normalised median deviation (NMAD)revealed the highest accuracy for the 1-m (RMSE = 1.55 m;NMAD = 0.44 m) and 5-m LiDAR DTMs (RMSE = 1.73 m;NMAD = 0.84 m). Vertical accuracy of the SRTM data was lower (RMSE = 6.98 m;NMAD = 5.27 m), but considerably higher than for the ASTER data (RMSE = 16.10 m;NMAD = 11.23 m). All datasets were affected by systematic distortions. Propagation of these errors and coarse horizontal resolution caused negative impacts on flow routing, stream network, and catchment delineation, and to a lower extent, on the distribution of slope values. These limitations should be carefully considered when applying DTMs for catchment hydrogeomorphological modelling

Assessing the effects of traditional soil conservation structures on sediment connectivity in Mediterranean catchments using remote sensing and gis

[eng] Understanding the sedimentary dynamics of the catchments is a central issue in Earth Sciences research because of its important implications on water resources management, agriculture, landscape evolution and ecosystems. Sediment transfer is strongly determined by natural factors such as climatology, lithology, vegetation or morphological characteristics of the catchment, but in the Mediterranean region the anthropogenic factors have a special relevance. For that reason, in the current context of Global Change, studying the impacts of changes in land uses and human activities on hydrosedimentary dynamics is a preferential scientific challenge. Traditionally, the sediment transfer efficiency of a catchment has been estimated by the sediment budget approach, which allows establishing the proportion of eroded materials reaching the catchment outlet. However, this methodological approach is insufficient to analyse the internal dynamics of the catchment since it does not provide information on spatio-temporal variability of the sediment flows occurring within it. In recent years, under the advent of new technologies for observation and analysis in geomorphology, the concept of sediment connectivity has emerged as a more adequate framework to analyse the (de-)coupling mechanisms for sediment transfer, their frequency and magnitude or their spatial and temporal feedbacks, allowing a better understanding of the effects of human activities and different anthropic elements on the internal sedimentary dynamics in a catchment. In this thesis, the effects of different traditional soil conservation structures on sediment connectivity were evaluated in two Mediterranean catchments under global change dynamics, representative of mountainous areas (Sa Font de la Vila, 4.8 km2) and lowlands (Can Revull, 1.4 km2). Spatio-temporal variability of sediment flows was analysed by combining the calculation of the morphometric index of connectivity proposed by Borselli et al. (2008) –using the method of Cavalli et al. (2013)– with different techniques for its validation, including field mapping, soil sample analysis and the measurement of erosion/deposition landforms by means of UAV aerial campaigns and automated digital photogrammetry. In the Sa Font de la Vila River catchment, the massive presence of terraces resulted in spatial patterns of sediment connectivity very different from other studies in mountainous catchments without terraces. Due to their morphological characteristics and their relative position within the drainage system, these structures generated (i) a general disconnection between the different compartments of the catchment and (ii) a concentration of water and sediment flows along preferential pathways promoted by a cascade effect of collapse within the terraced areas. 73% of the surveyed wall-failures were located on these trajectories with high IC values. This spatial matching was related to feedback dynamics, in which the failure of the walls increased the runoff concentration, which in turn accelerated the hydraulic processes causing their collapse. Accordingly, abandoned terraced areas showed more developed erosion processes, as well as lower soil quality indicators with respect to non-terraced areas. The occurrence of successive wildfires in Sa Font de la Vila was also identified as a relevant factor exacerbating these soil degradation processes. In the Can Revull Creek catchment, the design and configuration of traditional drainage systems promoted (i) the decoupling of overland flows within hillslopes, as well as the decoupling of the hillslope–alluvial plain and alluvial plain–channel linkages, and (ii) improved longitudinal connectivity along the artificial channel network. Field observations corroborated that, during frequent events of moderate magnitude, the combination of surface channels and tile drains enabled a rapid evacuation of water excess, decreasing surface runoff within the fields. However, during less frequent events of high magnitude (T=25 yrs.), the structures capacity was overflooded, activating new sediment linkages and increasing the effective area of the catchment and sediment delivery at the catchment outlet. During three consecutive flood events, changes in distribution of the sediment pathways were observed, increasing drainage density, as well as the length and depth of concentrated erosion landforms. This thesis revealed that, while well maintained, soil conservation structures act as anthropogenic controls of the catchment's sensitivity, reducing its structural connectivity and imposing high precipitation thresholds for the activation of water and sediment flows. However, its abandonment and degradation trigger feedback dynamics between structural and functional connectivity leading to changes into the spatiotemporal patterns of sediment fluxes and accelerating erosion and land degradation processes. Sediment connectivity proved to be a suitable conceptual framework to study the effects of these anthropic elements on sediment dynamics within catchments. The precise identification of sources, links and deposition zones as well as the mechanisms and the magnitude-frequency of sediment (de-)coupling processes may have applications for land management operations, maintenance and improvement of traditional soil conservation structures.[cat] Comprendre les dinàmiques sedimentàries en conques de drenatge és un tema d’investigació central en Ciències de la Terra per les importants implicacions que tenen sobre la gestió dels recursos hídrics, l'agricultura, l'evolució del paisatge i els ecosistemes. La transferència de sediment està fortament determinada per nombrosos factors naturals com ara la climatologia, la litologia, la vegetació o les característiques morfològiques de la conca. Cal afegir, emperò, que a la regió Mediterrània els factors antropogènics tenen una especial rellevància, fet pel qual i en l'actual context de Canvi Global, estudiar els impactes dels canvis en els usos del sòl i de les activitats humanes sobre les dinàmiques hidrosedimentàries suposa un repte científic preferencial. Tradicionalment, l'eficiència d'una conca a l’hora de transferir sediments s'ha estimat mitjançant el càlcul de balanços de sediment, que permeten establir la proporció de materials erosionats que arriben al punt de drenatge. No obstant això, aquest enfocament metodològic resulta insuficient per analitzar les dinàmiques internes de la conca ja que no proporciona informació sobre variabilitat espacio-temporal dels fluxos de sediment que es produeixen al seu interior. Recentment i amb l’adveniment de les noves tecnologies per a l’anàlisi i observació en Geomorfologia, el concepte connectivitat del sediment ha emergit com un marc conceptual més adequat per analitzar els mecanismes interns de (des-)acoblament dels processos de transferència de sediment, la seva freqüència i magnitud o la seva retroalimentació espacial i temporal, la qual cosa permet comprendre millor els efectes de les activitats humanes i de diferents elements antròpics. En aquesta tesi s’avaluen els efectes de diferents estructures tradicionals de conservació del sòl sobre la connectivitat del sediment a l'interior de dues conques mediterrànies sota dinàmiques del canvi global, representatives d’àrees muntanyoses (Sa Font de la Vila; 4,8 km2) i d’àrees planes (Can Revull, 1,4 km2). La variabilitat espacio-temporal dels fluxos de sediment es va analitzar combinant el càlcul de l'índex morfomètric de connectivitat proposat per Borselli et al. (2008) –usant el mètode de Cavalli et al. (2013)– amb diferents tècniques per a la seva validació, incloent cartografia de camp, anàlisi de mostres de sòl i mesures de formes d'erosió/deposició mitjançant campanyes aèries amb dron i fotogrametria digital automatitzada. A la conca del Torrent de sa Font de la Vila, la presència massiva de diferents tipus de terrasses va donar com a resultat patrons espacials de connectivitat de sediment molt diferents respecte als d’altres estudis en conques muntanyoses sense terrasses. Degut a les seves característiques morfològiques i a la seva posició relativa dins el sistema de drenatge, aquestes estructures van generar (i) una desconnexió general entre els diferents compartiments de la conca i (ii) una concentració dels fluxos d'aigua i sediment al llarg de trajectòries preferencials, associada al col·lapse en cascada dels murs de les terrasses. El 73% dels punts de col·lapse en els murs es van localitzar sobre aquests camins altament connectats. Aquesta correspondència espacial es va relacionar amb dinàmiques de retroalimentació a partir de les quals la caiguda dels murs genera una major concentració dels fluxos superficials que, al seu torn, afavoreix els processos hidràulics que causen aquesta caiguda. En conseqüència, les zones de terrasses abandonades van mostrar un desenvolupament més avançat de processos erosius i van exhibir indicadors de qualitat del sòl significativament més baixos en relació a zones sense terrasses. L'ocurrència de successius incendis forestals a Sa Font de la Vila també es va identificar com un factor rellevant que exacerba encara més aquests processos de degradació dels sòls. A la conca de Can Revull el disseny i configuració dels sistemes tradicionals de drenatge van afavorir (i) el desacoblament dels fluxos a l'interior dels vessants, així com el desacoblament vessant–plana al·luvial i plana al·luvial–canal, i (ii) una major connectivitat longitudinal al llarg la xarxa de canals artificials. Les observacions de camp van corroborar que, durant esdeveniments freqüents de moderada magnitud, la combinació de canals superficials i subsuperficials va facilitar un drenatge ràpid de l'excés d'aigua i, alhora, una disminució de l'escorrentia superficial a l'interior dels camps de cultiu. No obstant això, durant esdeveniments menys freqüents d'alta magnitud (T = 25 anys) es va sobrepassar la capacitat de les estructures, generant nous traçats de fluxos de sediment i un augment remarcable de l'àrea efectiva de la conca, així com d’exportació de sediments. Al llarg de tres esdeveniments d'inundació consecutius es van produir canvis en patrons de distribució dels fluxos superficials, augmentant la densitat de drenatge, així com la longitud i profunditat de les formes d'erosió concentrada. Aquesta tesi demostra que, mentre estan ben mantingudes, les estructures tradicionals de conservació del sòl actuen com a controls antropogènics de la sensitivitat de la conca, reduint la seva connectivitat estructural i imposant llindars de precipitació molt elevats per a l'activació de processos de transferència de sediment. No obstant això, la seva degradació desencadena dinàmiques de retroalimentació entre la connectivitat estructural i funcional que alteren els patrons espacio-temporals dels fluxos de sediment, accelerant els processos d'erosió i degradació del sòl. La connectivitat de sediments ha demostrat ser un marc conceptual adequat per estudiar els efectes de diferents elements antròpics sobre els fluxos de sediment a l'interior de les conques. La identificació precisa de zones de generació de sediment, de deposició i els mecanismes d’intercomunicació interzonals, així com la magnitud-freqüència dels processos de (des-)acoblament pot tenir aplicacions per a la gestió sostenible de terres o per al disseny d'actuacions que permetin reduir l'erosió i degradació dels sòls.[spa] Comprender las dinámicas sedimentarias en cuencas de drenaje es un tema central en la investigación en Ciencias de la Tierra debido a sus importantes implicaciones sobre la gestión de los recursos hídricos, la agricultura, la evolución del paisaje y los ecosistemas. La transferencia de sedimentos está fuertemente determinada por numerosos factores naturales tales como la climatología, la litología, la vegetación o las características morfológicas de la cuenca, pero en la región Mediterránea los factores antropogénicos tienen una especial relevancia. Por esa razón, en el actual contexto de Cambio Global, estudiar los impactos de los cambios en los usos del suelo y de las actividades humanas sobre las dinámicas hidrosedimentarias supone un reto científico preferencial. Tradicionalmente, la eficiencia de una cuenca al transferir sedimentos se ha estimado mediante el cálculo de balances de sedimento, que permiten establecer la proporción de materiales erosionados que alcanzan el punto de drenaje. Sin embargo, este enfoque metodológico resulta insuficiente para analizar las dinámicas internas de la cuenca ya que no proporciona información sobre la variabilidad espaciotemporal de los flujos de sedimento que se producen en su interior. En los años recientes y gracias al advenimiento de las nuevas tecnologías en el análisis y observación en Geomorfología, el concepto conectividad del sedimento ha emergido como un marco conceptual más adecuado para analizar los mecanismos internos de (des-)acoplamiento de los procesos de transferencia de sedimento, su frecuencia y magnitud o su retroalimentación espacial y temporal, permitiendo una mejor comprensión de los efectos de actividades humanas y distintos elementos antrópicos. En esta tesis se evalúan los efectos de distintas estructuras tradicionales de conservación del suelo sobre la conectividad del sedimento en el interior de dos cuencas mediterráneas bajo dinámicas del cambio global representativas de áreas montañosas (Sa Font de la Vila, 4,8 km2) y de áreas llanas (Can Revull, 1,4 km2). La variabilidad espaciotemporal de los flujos de sedimento se analizó combinando el cálculo del índice de conectividad de Borselli et al. (2008) –usando el método de Cavalli et al. (2013)– con distintas técnicas para su validación, incluyendo cartografía de campo, análisis de muestras de suelo y mediciones de formas de erosión/deposición mediante campañas aéreas con drone y fotogrametría digital automatizada. En la cuenca del Torrent de Sa Font de la Vila, la presencia masiva de distintos tipos de terrazas dio como resultado patrones espaciales de conectividad muy diferentes con respecto a otros estudios en cuencas sin terrazas. Debido a sus características morfológicas y a su posición relativa dentro del sistema de drenaje, estas estructuras generaron (i) una desconexión general entre los distintos compartimentos de la cuenca y (ii) una concentración de los flujos de agua y sedimento a lo largo de trayectorias preferenciales asociada al colapso en cascada de los muros de las terrazas. El 73% de los puntos de colapso en los muros se localizaron sobre estos caminos con altos valores de IC. Esta correspondencia espacial se relacionó con dinámicas de retroalimentación a partir de las cuales la caída de los muros genera una mayor concentración de la escorrentía que, a su vez, favorece los procesos hidráulicos que causan su caída. En consecuencia, las zonas de terrazas abandonadas mostraron un desarrollo más avanzado de procesos erosivos, y exhibieron indicadores de calidad del suelo significativamente más bajos con respecto a zonas sin terrazas. La ocurrencia de sucesivos incendios forestales en Sa Font de la Vila también se identificó como un factor relevante que exacerba aún más estos procesos de degradación de los suelos. En la cuenca de Can Revull, el diseño y configuración de los sistemas tradicionales de drenaje favorecieron (i) el desacoplamiento de los flujos en el interior de las laderas, así como una desconexión ladera−llanura aluvial y llanura aluvial−canal, y (ii) una mayor conectividad longitudinal a lo largo de la red de canales artificiales. Las observaciones de campo corroboraron que, durante eventos frecuentes de moderada magnitud, la combinación de canales superficiales y subsuperficiales facilita un drenaje rápido del exceso de agua y, a su vez, una disminución de la escorrentía superficial en el interior de los campos de cultivo. Sin embargo, durante eventos menos frecuentes de alta magnitud (T=25 años) se sobrepasó la capacidad de las estructuras, generando nuevos trazados de flujo de sedimento y un aumento remarcable del área efectiva de la cuenca, así como de la exportación de sedimento. A lo largo de tres eventos de inundación consecutivos se produjeron cambios en patrones de distribución de los flujos superficiales, aumentando la densidad de drenaje, así como la longitud y profundidad de las formas de erosión concentrada. Esta tesis reveló que, mientras están bien mantenidas, las estructuras de conservación del suelo actúan como controles antropogénicos de la sensitividad de la cuenca, reduciendo su conectividad estructural e imponiendo umbrales de precipitación muy elevados para la activación de procesos de transferencia de sedimento. Sin embargo, su abandono y degradación desencadena dinámicas de retroalimentación entre la conectividad estructural y funcional que alteran los patrones espaciotemporales de los flujos de sedimento, acelerando los procesos de erosión y degradación del suelo. La conectividad del sedimento demostró ser un marco conceptual adecuado para estudiar los efectos de estos elementos antrópicos sobre los flujos de sedimento en el interior de las cuencas. La identificación precisa de las zonas de generación del sedimento, de deposición y los mecanismos de intercomunicación interzonales, así como la magnitud–frecuencia de los procesos de (des-)acoplamiento de sedimentos puede tener aplicaciones para la gestión sostenible de tierras o para el mantenimiento y mejora de las estructuras tradicionales de conservación del suelo

Rainfall-runoff relationship at different time scales in a mid-mountainous Mediterranean catchment

(1) Mediterranean Ecogeomorphological and Hydrological Connectivity Research Team (http://medhycon.uib.cat), Department of Geography, University of the Balearic Islands, Carretera de Valldemossa Km 7.5 07122, Palma, Spain, (2) Institute of Agro-Environmental and Water Economy Research –INAGEA, University of the Balearic Islands, (3) Institute of Earth and Environmental Science, University of Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam-Golm, Germany, (4) Institute of Environmental Assessment and Water Research (IDAEA), Spanish Research Council (CSIC), Jordi Girona 18, 08034 Barcelona, Spain Mediterranean catchments are characterized by high inter-intra annual precipitation variability and summer drought. The hydrological regime is characterized by ephemeral behaviour due to the direct rainfall-runoff relationship. Furthermore, extreme precipitations can generate an amount of rainfall higher than 200 mm in 24 hours with short response time. These events occurred normally under wet soil moisture conditions. The Mediterranean catchment morphology is a favourable factor for flash floods: short catchments with a high gradient slope. Others factor that condition the hydrological regime are the presence of limestone lithology and the impact of human activities on fluvial systems as geomorphological changes in channels and flood plains. The aim of this study is analyse the hydrological response of five hydrological years (2012-17) in an agricultural headwater catchment (i.e. < 4 km2) at different time scales. Rainfall-runoff relationship was carried out at annual and seasonal scale through the flow duration computation, the variability index, 30/70 ratio, quick flow response ratio and base flow index. The rainfall-runoff relationship at event scale was carried out through a Pearson correlation matrix using different variables extracted from the hyetograph and hydrograph. These variables were placed into two groups: a) antecedent conditions and b) event conditions. The correlation results determined the involved factors in the hydrological response. At annual scale total flow was present for 42.8% of the time and quick flow was 1.4%. The Variability index value (0.64) was higher than catchments with high dynamics storage (Vi < 0.5). At season scale, winter with 90.6%, showed the highest discharge presence. This highest discharge percentage duration generated a sustained water storage (Vi: 0.55) and increased the soil moisture from autumn getting favourable conditions for runoff generation. Because of that, winter had the highest quick flow duration (3.1%) and also the 30/70 denotes an increase of the flow variability. Autumn and spring had lower percentage of discharge duration than winter, 53% and 41% respectively. Autumn is the season after the dry season when starts again the wet period getting favourable conditions for runoff generation. Spring denotes the importance of the accumulated precipitation contribution of the wet seasons, also indicated for the highest seasonal BFI (0.7). Summer presented flow and quick flow the 0.93% and 0.21% of time respectively. At event scale, peak discharge, mean discharge, runoff and quick flow showed significant correlations (p<0.01) with the total precipitation and correlated with antecedent precipitation of one and three days (p<0.05). Baseflow variables correlated with antecedent precipitation until 15 days before flood date. Peak discharge was the unique hydrological variable that correlated with maximum rainfall intensity 30’. That indicated that a shorter period of rainfall intensity (15min) is not enough to generate a response. So, for peak discharge a combination of two mechanisms is needed to generate runoff: a) surface runoff occur when rainfall intensity exceeds infiltration capacity and b) surface runoff is produced by precipitation over the area where water table is at the surface.Peer reviewe

Effects of check dams on sediment dynamics in a debris-flow catchment

The Moscardo Torrent (catchment area 4.1 km2, range in elevation between 890 and 2043 m), a small stream in the Eastern Italian Alps, displays a high frequency of debris flows (commonly one event per year) that deliver large amounts of sediment to the receiving stream, and cause concerns for infrastructures located on the alluvial fan and near the confluence. Over the last decades, hydraulic control works were implemented in the main channel to limit bed erosion and to stabilize channel banks. Although the objectives of training works have been only partly achieved, check dams and hillslope stabilization works have affected the sediment transfer from hillslopes to the channels and along the main channel. The effects of hydraulic control works were investigated by means of multitemporal Structure from Motion (SfM) surveys over an area exposed to debris-flow dynamics in which two new check dams were built. Ground-based SfM surveys were taken before and after three debris-flow events (occurred between June and July 2016), allowing the generation of four high-resolution Digital Elevation Models (DEMs). Geomorphic changes caused by the debris-flow events have been assessed in order to produce the DEM of differences (DoDs with a 0.2 m spatial resolution) that allowed estimating erosion and deposition volumes in the study area. Furthermore a debris-flow monitoring system has been in operation in the Moscardo Torrent; the analysis of the videos and of the hydrographs recorded by ultrasonic sensors permitted to assess the debris-flow volumes. These estimates were used to characterize the magnitude of events in support of the topographic analysis. By examining the changing pattern of erosion and deposition over time it was possible to understand the check dams\u2019 effects on sediment dynamics. Preliminary results show that the new check dams effectively stored sediment transported by the three debris flows. However, once the check dams will be completely filled, they will lose their functionality, letting sediment flow downstream along preferential paths defined by the torrent control works and by the morphology of debris-flow deposits. Moreover, debris-flow lobes deposited upstream of the check dams could act as sediment sources further increasing downstream debris-flow magnitude

Changes in Soil Quality and Hydrological Connectivity Caused by the Abandonment of Terraces in a Mediterranean Burned Catchment

Wildfires and agricultural activities are relevant factors affecting soil quality, hydrological cycle and sedimentary dynamics. Land abandonment leads to afforestation, which increases fire risk and land degradation. However, no studies have yet evaluated the effect of combining the two factors, which occur frequently in Mediterranean ecosystems. This study assessed the changes in soil quality caused by the abandonment of terraces in two microcatchments (&lt;2.5 ha) affected distinctly by wildfires (once and twice burned) and in an unburned control microcatchment by analyzing soil quality parameters, biochemical indices and spatial patterns of hydrological and sediment connectivity. Soil samples were collected in thirty-six plots (25 m2) representing terraced and non-terraced areas within these microcatchments. Unburned non-terraced plots had higher organic matter content and higher microbiological and enzymatic activities than other plots. Plots in abandoned terraces had lower soil quality indices, regardless of the fire effect. Land abandonment induced changes in the spatial patterns of hydrological connectivity, leading to concentrated runoff, enhanced erosion and soil degradation. Fire also negatively affected soil quality in both terraced and non-terraced plots. However, microbiological communities had different positive post-fire recovery strategies (growth and activity), depending on the previous soil conditions and land uses, which is indicative of the resilience of Mediterranean soil ecosystems

Multiple Temporal Scales Assessment in the Hydrological Response of Small Mediterranean-Climate Catchments

27 Pags.- 10 Figs.- 7 Tabls. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Mediterranean-climate catchments are characterized by significant spatial and temporal hydrological variability caused by the interaction of natural as well human-induced abiotic and biotic factors. This study investigates the non-linearity of rainfall-runoff relationship at multiple temporal scales in representative small Mediterranean-climate catchments (i.e., <10 km2) to achieve a better understanding of their hydrological response. The rainfall-runoff relationship was evaluated in 43 catchments at annual and event—203 events in 12 of these 43 catchments—scales. A linear rainfall-runoff relationship was observed at an annual scale, with a higher scatter in pervious (R2: 0.47) than impervious catchments (R2: 0.82). Larger scattering was observed at the event scale, although pervious lithology and agricultural land use promoted significant rainfall-runoff linear relations in winter and spring. These relationships were particularly analysed during five hydrological years in the Es Fangar catchment (3.35 km2; Mallorca, Spain) as a temporal downscaling to assess the intra-annual variability, elucidating whether antecedent wetness conditions played a significant role in runoff generation. The assessment of rainfall-runoff relationships under contrasted lithology, land use and seasonality is a useful approach to improve the hydrological modelling of global change scenarios in small catchments where the linearity and non-linearity of the hydrological response—at multiple temporal scales—can inherently co-exist in Mediterranean-climate catchments.This work was supported by the research project CGL2017-88200-R “Functional hydrological and sediment connectivity at Mediterranean catchments: global change scenarios –MEDhyCON2” funded by the Spanish Ministry of Science, Innovation and Universities, the Spanish Agency of Research (AEI) and the European Regional Development Funds (ERDF). The contribution of Jérôme Latron was supported by the research project PCIN-2017-061/AEI also funded by the Spanish Government. Josep Fortesa has a contract funded by the Ministry of Innovation, Research and Tourism of the Autonomous Government of the Balearic Islands (FPI/2048/2017). Julián García-Comendador is in receipt of a pre-doctoral contract (FPU15/05239) funded by the Spanish Ministry of Education, Culture and Sport. Miquel Tomàs-Burguera acknowledges the support from the project CGL2017-83866-C3-3-R financed by the European Regional Development Funds (ERDF) and the Spanish Ministry of Science, Innovation and Universities. Jaume Company is in receipt of Young Qualified Program fund by Employment Service of the Balearic Islands and European Social Fund (SJ-QSP 48/19). Aleix Calsamiglia acknowledges the support from the Spanish Ministry of Science, Innovation and Universities through a pre-doctoral contract (BES-2013-062887).Peer reviewe

Comparison of stage/discharge rating curves derived from different recording systems: Consequences for streamflow data and water management in a Mediterranean island

Obtaining representative hydrometric values is essential for characterizing extreme events, hydrological dynamics and detecting possible changes on the long-term hydrology. Reliability of streamflow data requires a temporal continuity and a maintenance of the gauging stations, which data are affected by epistemic and random sources of error. An assessment of discharge meterings' and stage-discharge rating curves' uncertainties were carried out by comparing the accuracy of the measuring instruments of two different hydrometric networks (i.e., one analogical and one digital) established in the same river location at the Mediterranean island of Mallorca. Furthermore, the effects of such uncertainties were assessed on the hydrological dynamics, considering the significant global change impacts beset this island. Evaluation was developed at four representative gauging stations of the hydrographic network with analogic (≈40 years) and digital (≈10 years) data series. The study revealed that the largest source of uncertainty in the analogical (28 to 274%) and in the digital (17–37%) networks were the stage-discharge rating curves. Their impact on the water resources was also evaluated at the event and annual scales, resulting in an average difference of water yields of 183% and 142% respectively. Such improvement on the comprehension of hydrometric networks uncertainties will dramatically benefit the interpretation of the long-term streamflow by providing better insights into the hydrologic and flood hazard planning, management and modelling. © 2019This work was supported by a research contract funded in 2014 by the Directorate-General of Water Resources (Department of Environment, Agriculture, and Fishery of the Balearic Autonomous Government) and the research project CGL2012-32446 “Assessing hydrological and sediment connectivity in contrasting Mediterranean catchments. Impacts of Global Change-MEDhyCON” funded by the Ministry of Economy and Competitiveness of the Spanish Government. The contribution of Jérôme Latron was supported by the research project PCIN-2017-061/AEI also funded by the Ministry of Economy and Competitiveness of the Spanish Government. Josep Fortesa has a contract funded by Ministry of Innovation, Research and Tourism of the Autonomous Government of the Balearic Islands (FPI/2048/2017). He also acknowledges the support from “la Caixa” Foundation through a mobility grant for young researchers at the Universitat de les Illes Balears with announcement reference number 3111. Julián García-Comendador is in receipt of a pre-doctoral contract (FPU15/05239) funded by the Spanish Ministry of Education and Culture. Aleix Calsamiglia acknowledges the support from the Spanish Ministry of Economy and Competitiveness through a pre-doctoral contract (BES-2013-062887). José Andrés López-Tarazón is in receipt of a Vicenç Mut postdoctoral fellowship (CAIB PD/038/2016) funded by the Vice-presidency and Ministry of Innovation, Research and Tourism of the Autonomous Government of the Balearic Islands. Meteorological data were facilitated by the Spanish Meteorological Agency (AEMET). Authors thank the three anonymous reviewers and the Guest Editor, Prof. Axel Bronstert, for their constructive comments and suggestions that significantly improved the final version of the paper.Peer reviewe

Assessing the effects of check dams on sediment dynamics in a debris-flow catchment through SfM technique

7siThe Moscardo Torrent (eastern Italian Alps) is a small rugged catchment (drainage area 4.1 km2, range in elevation between 890 and 2043 m) frequently affected by debris flows that deliver large amounts of sediment to the receiving stream, and cause concerns for infrastructures located on the alluvial fan and near the confluence. Over the last decades, hydraulic control works were implemented in the main channel to limit bed erosion and to stabilize channel banks. Although the objectives of training works have been only partly achieved, check dams and hillslope stabilization works have affected the sediment transfer from hillslopes to the channels and along the main channel. The effects of hydraulic control works were investigated by means of multi-temporal Structure from Motion (SfM) surveys based on images taken from the ground and UAV. The ground and air based surveys were carried out over a channel reach in which two check dams have recently been built. SfM surveys were taken before and after three debris-flow events (occurred between June and July 2016), allowing the generation of four high-resolution Digital Elevation Models (DEMs). Geomorphic changes caused by the debris-flow events have been assessed in order to produce the DEM of Differences (DoDs with a 0.2 m spatial resolution) that allowed estimating erosion and deposition volumes in the study area. Furthermore a debris-flow monitoring system has been in operation in the Moscardo Torrent; the analysis of the videos and of the hydrographs recorded by ultrasonic sensors permitted to assess the debris-flow volumes. These estimates were used to characterize the magnitude of events in support of the topographic analysis. By examining the changing pattern of erosion and deposition over time it was possible to understand the check dams’ effects on sediment dynamics. The results show that the new check dams effectively stored sediment transported by the three debris flows. However, once the check dams have been completely filled, they lost their functionality, letting sediment flow downstream along paths drawn accidentally by the torrent control works and by the morphology of debris-flow deposits. Moreover, debris-flow lobes deposited upstream of the check dams could act as sediment sources further increasing downstream debris-flow magnitude.reservedmixedCucchiaro, Sara; Beinat, Alberto; Calsamiglia, Aleix; Cavalli, Marco; Cazorzi, Federico; Crema, Stefano; Marchi, LorenzoCucchiaro, Sara; Beinat, Alberto; Calsamiglia, Aleix; Cavalli, Marco; Cazorzi, Federico; Crema, Stefano; Marchi, Lorenz

Ecogeomorfología y drones como instrumentos de gestión dinámica post-incendio. El caso de la comarca del Pariatge, Mallorca

Els incendis forestals s&oacute;n considerats un dels factors causals m&eacute;s importants en els processos de desertificaci&oacute;. Els territoris insulars com Mallorca s&oacute;n particularment sensibles als impactes antr&ograve;pics, per la seva major fragilitat socioecol&ograve;gica. L&rsquo;increment de superf&iacute;cie cremada a Mallorca d&rsquo;en&ccedil;&agrave; el 2011 esperoneja a vincular gesti&oacute; forestal i recerca amb interdisciplinarietat i aven&ccedil;os tecnol&ograve;gics. L&rsquo;ecogeomorfologia permet investigar el paper dels processos geomorfol&ograve;gics en la recuperaci&oacute; de la vegetaci&oacute;. Endem&eacute;s, la introducci&oacute; dels vehicles aeris no tripulats com a instruments de teledetecci&oacute; presenta noves oportunitats en el monitoratge de processos ambientals. Aquest article pret&eacute;n dilucidar el potencial de l&rsquo;ecogeomorfologia i els drons per aplicar una gesti&oacute; postincendi m&eacute;s efectiva i din&agrave;mica, integrant la capacitat de resili&egrave;ncia dels ecosistemes amb la connectivitat dels sediments per restaurar el paisatge.Paraules clau: gesti&oacute; postincendi, connectivitat dels sediments, ecofisiologia vegetal, UAV, ecosistemes mediterranis.Ecogeomorphology and drones as dynamic tools for post-fire management. The experience in the Pariatge County, Mallorca Wildfires are one of the most significant driving factors in desertification processes. Furthermore, insular territories such Mallorca are more affected by human impacts due to their intrinsic socioecological fragility. The increase of burned surface area since 2011in Balearic Islands involves a challenge in which forest management and research through interdisciplinary and technological advances should be joined. Ecogeomorphology is an emergent discipline which allows investigating the role of geomorphic processes in the vegetation recovery. Additionally, the introduction of unmanned aerial vehicles as remotesensing tools offers new and exciting opportunities for monitoring environmental processes. This paper pretends to elucidate the potential of ecogeomorphology and drones to implement more effective and dynamic post-fire management integrating both the resilience capacity of ecosystems with sediment connectivity for landscape restoration.Keywords: post-fire management, sediment connectivity, vegetal ecophysiology, UAVs, Mediterranean ecosystems.Los incendios forestales son uno de los factores causales m&aacute;s importantes en los procesos de desertificaci&oacute;n. Los territorios insulares como Mallorca son particularmente sensibles a los impactos antr&oacute;picos, a causa de su mayor fragilidad socioecol&oacute;gica. El incremento de superficie quemada en Mallorca desde el a&ntilde;o 2011 incita vincular gesti&oacute;n forestal e investigaci&oacute;n a trav&eacute;s de interdisciplinariedad y avances tecnol&oacute;gicos. La ecogeomorfolog&iacute;a permite investigar el papel de los procesos geomorfol&oacute;gicos en la recuperaci&oacute;n de lavegetaci&oacute;n. Adem&aacute;s, la introducci&oacute;n de veh&iacute;culos a&eacute;reos no tripulados como instrumentos de teledetecci&oacute;n presenta nuevas oportunidades en la monitorizaci&oacute;n de procesos ambientales. Este art&iacute;culo pretende dilucidar el potencial de la ecogeomorfolog&iacute;a y de los drones para aplicar una gesti&oacute;n post-incendio m&aacute;s efectiva y din&aacute;mica, integrando la capacidad de resiliencia de los ecosistemas con la conectividad de los sedimentos para restaurar el paisaje.Palabras clave: gesti&oacute;n post-incendio, conectividad de sedimentos, ecofisiolog&iacute;avegetal, UAVs, ecosistemas mediterr&aacute;neos