Flood quantiles scaling with upper soil hydraulic properties for different land uses at catchment scale

[EN] Changes in land use within a catchment are among the causes of non-stationarity in the flood regime, as they modify the upper soil physical structure and its runoff production capacity. This paper analyzes the relation between the variation of the upper soil hydraulic properties due to changes in land use and its effect on the magnitude of peak flows: (1) incorporating fractal scaling properties to relate the effect of the static storage capacity (the sum of capillary water storage capacity in the root zone, canopy interception and surface puddles) and the upper soil vertical saturated hydraulic conductivity on the flood regime; (2) describing the effect of the spatial organization of the upper soil hydraulic properties at catchment scale; (3) examining the scale properties in the parameters of the Generalized Extreme Value (GEV) probability distribution function, in relation to the upper soil hydraulic properties. This study considered the historical changes of land use in the Combeima River catchment in South America, between 1991 and 2007, using distributed hydrological modeling of daily discharges to describe the hydrological response. Through simulation of land cover scenarios, it was demonstrated that it is possible to quantify the magnitude of peak flows in scenarios of land cover changes through its Wide-Sense Simple Scaling with the upper soil hydraulic properties.This research was funded partially by the COLCIENCIAS 567 doctoral fellowship program, Universidad del Tolima project 1300213 and Universidad de Ibague (Colombia) project 12-262-COL00, and by Universitat Politecnica de Valencia (Spain) and by the Spanish Research Project ECO-TETIS (ref. CGL2011-28776-C02-01) and TETIS-MED (ref. CGL2014-58127-C3-3-R). Thanks to The Shuttle Radar Topography Mission NASA, IDEAM and IGAC in Colombia, for providing digital elevation model, streamflow, rainfall data, and soil study of the Tolima Region.Peña-Rojas, LE.; Barrios Peña, MI.; Francés, F. (2016). Flood quantiles scaling with upper soil hydraulic properties for different land uses at catchment scale. Journal of Hydrology. 541:1258-1272. https://doi.org/10.1016/j.jhydrol.2016.08.031S1258127254

A review of applied methods in Europe for flood-frequency analysis in a changing environment

The report presents a review of methods used in Europe for trend analysis, climate change projections and non-stationary analysis of extreme precipitation and flood frequency. In addition, main findings of the analyses are presented, including a comparison of trend analysis results and climate change projections. Existing guidelines in Europe on design flood and design rainfall estimation that incorporate climate change are reviewed. The report concludes with a discussion of research needs on non-stationary frequency analysis for considering the effects of climate change and inclusion in design guidelines. Trend analyses are reported for 21 countries in Europe with results for extreme precipitation, extreme streamflow or both. A large number of national and regional trend studies have been carried out. Most studies are based on statistical methods applied to individual time series of extreme precipitation or extreme streamflow using the non-parametric Mann-Kendall trend test or regression analysis. Some studies have been reported that use field significance or regional consistency tests to analyse trends over larger areas. Some of the studies also include analysis of trend attribution. The studies reviewed indicate that there is some evidence of a general increase in extreme precipitation, whereas there are no clear indications of significant increasing trends at regional or national level of extreme streamflow. For some smaller regions increases in extreme streamflow are reported. Several studies from regions dominated by snowmelt-induced peak flows report decreases in extreme streamflow and earlier spring snowmelt peak flows. Climate change projections have been reported for 14 countries in Europe with results for extreme precipitation, extreme streamflow or both. The review shows various approaches for producing climate projections of extreme precipitation and flood frequency based on alternative climate forcing scenarios, climate projections from available global and regional climate models, methods for statistical downscaling and bias correction, and alternative hydrological models. A large number of the reported studies are based on an ensemble modelling approach that use several climate forcing scenarios and climate model projections in order to address the uncertainty on the projections of extreme precipitation and flood frequency. Some studies also include alternative statistical downscaling and bias correction methods and hydrological modelling approaches. Most studies reviewed indicate an increase in extreme precipitation under a future climate, which is consistent with the observed trend of extreme precipitation. Hydrological projections of peak flows and flood frequency show both positive and negative changes. Large increases in peak flows are reported for some catchments with rainfall-dominated peak flows, whereas a general decrease in flood magnitude and earlier spring floods are reported for catchments with snowmelt-dominated peak flows. The latter is consistent with the observed trends. The review of existing guidelines in Europe on design floods and design rainfalls shows that only few countries explicitly address climate change. These design guidelines are based on climate change adjustment factors to be applied to current design estimates and may depend on design return period and projection horizon. The review indicates a gap between the need for considering climate change impacts in design and actual published guidelines that incorporate climate change in extreme precipitation and flood frequency. Most of the studies reported are based on frequency analysis assuming stationary conditions in a certain time window (typically 30 years) representing current and future climate. There is a need for developing more consistent non-stationary frequency analysis methods that can account for the transient nature of a changing climate

Hydrological Modelling and Climate Change Impact Assessment on Future Floods in the Norwegian Arctic Catchments

Climate change is expected to alter the hydrological cycle in the Arctic, which would result in the increase in intensity and frequency of hydrological extreme events such as flooding. Noticeably, the changes in flooding due to climate change would severely affect human life, infrastructures, the environment, ecosystem, and socio-economic development in the impacted areas. Hydrological models are state-of-the-art tools for assessing the impact of climate change on hydrological processes. However, performing hydrological simulation/projection in the Arctic is challenging because of the complex hydrological processes and data-sparse features in the region. In consideration of those issues, this PhD research aims: (1) to assess the performances of hydrological models in the Arctic, (2) to investigate the alternative weather inputs for running the hydrological models in the Arctic region with scattered monitoring data, (3) to evaluate the effects of the models’ structure and parameterization and the spatial resolution of weather inputs on the results of hydrological simulations, and (4) to project future hydrological events under climate change impacts using the current hydrological model, and analyse the reliability/uncertainty of the projection. To fulfil the research’s objectives, several methodologies were applied. Firstly, a comprehensive review was conducted to address the current capacities and challenges of twelve well-known hydrological models, including surface hydrological models and subsurface hydrological models/groundwater models/cryo-hydrogeological models. These models have previously been applied or have the potential for application in the Arctic. Next, the physically based, semi-distributed model, SWAT (soil and water assessment tool), was selected as a suitable model, among other potential models, to assess its performance for hydrological simulations and to verify the potential application of reanalysis weather data. Moreover, the SWAT was coupled with multiple ensemble global and regional climate models’ simulations to project the future hydrological impacts under climate change (in 2041-2070). The study areas were mainly focused in the Norwegian Arctic catchments

Impact Evaluation of Future Climate and Land Use Scenarios on Water and Sediment Regime using Distributed Hydrological Modelling in a Tropical Rainforest Catchment in West Java (Indonesia)

[EN] Climate change has occurred in Indonesia, for example, increasing the surface air temperature, including in the Upper Citarum watershed. This phenomenon leads to a lack of water in the dry season, which lowers agriculture production and remains a great obstacle for agricultural activity. Meanwhile, human activity has produced severe LULC changes within the Upper Citarum watershed. This occurs due to the demands of the ever-increasing population growth in the region. As a result, rice field and forested areas have been sacrificed to compensate the urban increment. The general objective of this dissertation is to understand and analyze the impact of climate and LULC changes on the hydrological process and their relationship with historical and future changes by using spatially distributed modeling on the Upper Citarum tropical catchment. The distributed model TETIS has been implemented to obtain the results of past and future scenarios on the water and sediment cycles. Annual historical bathymetries in the reservoir were used to calibrate and validate the sediment sub-model involving Miller's density evolution and trap efficiency of Brune's equation. Climate change has been considered under RCP 45 and RCP 85 trajectories. Meanwhile, to overcome the LULC problem, historical and future LULCs have been studied. LCM model was used to forecast the LULC in 2029. The forecasted results of LCM model show, on one hand, a continuation in the expansion of urban areas at the expense of the contiguous rice fields. The results determined that deforestation and urbanization were the most influential factors for the alteration of the hydrological and sedimentological processes in the Upper Citarum Catchment. Thus, it decreases evapotranspiration, increases water yield by increasing all its components; overland flow, interflow and baseflow. The changes in LULC are currently producing and will produce in the future, a relatively small increment of erosion rates, increasing the area exceeds Tsl erosion. Sediment yield will increase in 2029 as the result of erosion increment. Other LULC scenarios such as conservation, government plan and natural vegetation scenarios are expected to have an increment in total evapotranspiration, the water yield is expected to decrease. Flood regime, erosion and sedimentation are reduced dramatically. Hence, it leads to a massive increment of reservoir and hydropower lifetime signed by a very long period of the lifetime. Climate change alters the magnitude of water balance and can be identified from the shift of infiltration, overland flow, interflow, baseflow and water yield. Those increments finally change the flood regime, catchment erosion. RCP 85 trajectory gives a bigger impact compared to RCP 45 trajectory on hydrological and sediment cycle. . LULC change results a bigger impact on water balance, flood regime, erosion and sedimientation. The combination of climate and LULC change give a bigger impact on the flows of water balance, erosion, flood, sedimentation and will be catastrophic for the hydropower operation of the Saguling Dam.[ES] El cambio climático ha afectado a Indonesia, por ejemplo, incrementando la temperatura del aire en la superficie, incluso en la cuenca del Upper Citarum. Este fenómeno conduce a la falta de agua en la estación seca, reduciendo la producción agrícola lo que es un gran obstáculo para su actividad. Además, la actividad humana ha producido cambios severos en LULC en la cuenca del Upper Citarum, Indonesia. Esto se debe al elevado crecimiento de la población en la región, por el que se han convertido campos de arroz y áreas boscosas en suelo urbano. De esta forma, el objetivo general de esta tesis es comprender y analizar el impacto de los cambios climáticos y LULC en el proceso hidrológico y su relación con los cambios históricos y futuros mediante el uso de modelos distribuidos espacialmente en la cuenca tropical del Upper Citarum. El modelo distribuido TETIS se ha implementado para obtener los resultados de escenarios pasados y futuros en los ciclos de agua y sedimentos. Se usaron batimetrías históricas anuales en el embalse para calibrar y validar el submodelo de sedimentos que involucra la evolución de la densidad de Miller y la eficiencia de retención de la ecuación de Brune. Con el fin de arrojar más luz sobre estos problemas, el escenario de cambio climático se ha implementado en base al modelo de cambio climático bajo las trayectorias RCP 45 y RCP 85. Además, para intentar resolver el problema LULC, también se ha implementado el LULC histórico y futuro. El modelo LCM se usó para pronosticar el LULC en 2029 y los resultados muestran, por un lado, una continuación en la expansión de las áreas urbanas a expensas de los arrozales contiguos. Los resultados determinaron que la deforestación y la urbanización fueron los factores más influyentes para la alteración de los procesos hidrológicos y sedimentológicos en la cuenca del Upper Citarum. Por lo tanto, disminuye la evapotranspiración, aumenta la producción de agua al aumentar todos sus componentes; escorrentía, interflujo y flujo base. Los cambios en LULC están produciendo y producirán, un incremento relativamente pequeño de las tasas de erosión, aumentando el área excede la erosión de Tsl. La producción de sedimentos aumentará en 2029 como resultado del incremento de la erosión. Se espera que otros escenarios de LULC como la conservación, el plan gubernamental y los escenarios de vegetación natural tengan un incremento en la evapotranspiración total, y se espera que la producción de agua disminuya. El régimen de inundación, la erosión y la sedimentación se reducen drásticamente. Por lo tanto, habrá un incremento de la vida útil del embalse y la energía hidroeléctrica. El cambio climático altera la magnitud del equilibrio hídrico y puede identificarse a partir del cambio de infiltración, escorrentía, interflujo, flujo base y producción de agua. Esos incrementos finalmente cambian el régimen de inundación y erosión de la cuenca. La trayectoria RCP 85 tiene un mayor impacto en comparación con la trayectoria RCP 45 en el ciclo hidrológico y de sedimentos. El cambio de LULC tiene un mayor impacto en el balance hídrico, el régimen de inundación, la erosión y la sedimentación. La combinación del cambio climático y LULC tiene un mayor impacto en los flujos de equilibrio hídrico, erosión, inundación, sedimentación y será catastrófico para la operación hidroeléctrica de la presa Saguling.[CA] El canvi climàtic ha afectat Indonèsia, per exemple, incrementant la temperatura de l'aire en la superfície, inclús en la conca de l'Upper Citarum. Aquest fenomen conduïx a la falta d'aigua en l'estació seca, reduint la producció agrícola, el que és un gran obstacle per a la seua activitat. A més, l'activitat humana ha produït canvis severs en LULC en la conca de l'Upper Citarum, Indonèsia. Açò es deu a l'elevat creixement de la població en la regió, motiu pel qual s'han anat convertint camps d'arròs i àrees boscoses en sòl urbà. D'aquesta manera, l'objectiu general d'aquesta tesi és comprendre i analitzar l'impacte dels canvis climàtics i LULC en el procés hidrològic i la seua relació amb els canvis històrics i futurs per mitjà de l'ús de models distribuïts espacialment en la conca tropical de l'Upper Citarum. El model distribuït TETIS s'ha implementat per a obtindre els resultats d'escenaris passats i futurs en els cicles de l'aigua i sediments. Es van usar batimetries històriques anuals en l'embassament per a calibrar i validar el submodel de sediments que involucra l'evolució de la densitat de Miller i l'eficiència de retenció de l'equació de Brune. Amb la finalitat de donar més llum a aquests problemes, l'escenari de canvi climàtic s'ha implementat basant-se en el model de canvi climàtic davall les trajectòries RCP 45 i RCP 85. A més, per a intentar resoldre el problema LULC, també s'ha implementat el LULC històric i futur. El model LCM es va usar per a pronosticar el LULC en 2029 i els resultats mostren, d'una banda, una continuació en l'expansió de les àrees urbanes a costa dels arrossars contigus. Els resultats van determinar que la desforestació i la urbanització van ser els factors més influents per a l'alteració dels processos hidrològics i sedimentològics en la conca de l'Upper Citarum. Per tant, disminuïx l'evapotranspiració, augmenta la producció d'aigua en augmentar tots els seus components; escorrentia, interflux i flux base. Els canvis en LULC estan produint i produiran, un increment relativament xicotet de les taxes d'erosió, augmentant l'àrea excedix l'erosió de Tsl. La producció de sediments augmentarà en 2029 com a resultat de l'increment de l'erosió. S'espera que altres escenaris de LULC com la conservació, el pla governamental i els escenaris de vegetació natural tinguen un increment en l'evapotranspiració total, i s'espera que la producció d'aigua disminuïsca. El règim d'inundació, l'erosió i la sedimentació es reduïxen dràsticament. Per tant, hi haurà un increment de la vida útil de l'embassament i l'energia hidroelèctrica. El canvi climàtic altera la magnitud de l'equilibri hídric i pot identificar-se a partir del canvi d'infiltració, escorrentia, interflux, flux base i producció d'aigua. Eixos increments finalment canvien el règim d'inundació i erosió de la conca. La trajectòria RCP 85 té un major impacte en comparació amb la trajectòria RCP 45 en el cicle hidrològic i de sediments. El canvi de LULC té un major impacte en el balanç hídric, el règim d'inundació, l'erosió i la sedimentació. La combinació del canvi climàtic i LULC té un major impacte en els fluxos d'equilibri hídric, erosió, inundació, sedimentació i serà catastròfic per a l'operació hidroelèctrica de la presa Saguling.thank the Directorate General of Higher Education of Indonesia (DIKTI), for granting me the opportunity to pursue PhD study and adventure in Europe. The authors are also thankful to the Spanish Ministry of Economy and Competitiveness through the research projects TETISMED (CGL2014-58127-C3-3-R) and TETISCHANGE (RTI2018-093717-B-I00).Siswanto, SY. (2020). Impact Evaluation of Future Climate and Land Use Scenarios on Water and Sediment Regime using Distributed Hydrological Modelling in a Tropical Rainforest Catchment in West Java (Indonesia) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/153152TESI

Uncertainty analysis of 100-year flood maps under climate change scenarios

Floods are natural disastrous hazards that throughout history have had and still have major adverse impacts on people’s life, economy, and the environment. One of the useful tools for flood management are flood maps, which are developed to identify flood prone areas and can be used by insurance companies, local authorities and land planners for rescue and taking proper actions against flood hazards. Developing flood maps is often carried out by flood inundation modeling tools such as 2D hydrodynamic models. However, often flood maps are generated using a single deterministic model outcome without considering the uncertainty that arises from different sources and propagates through the modeling process. Moreover, the increasing number of flood events in the last decades combined with the effects of global climate change requires developing accurate and safe flood maps in which the uncertainty has been considered. Therefore, in this thesis the uncertainty of 100-year flood maps under 3 scenarios (present and future RCP4.5 and RCP8.5) is assessed through intensive Monte Carlo simulations. The uncertainty introduced by model input data namely, roughness coefficient, runoff coefficient and precipitation intensity (which incorporates three different sources of uncertainty: RCP scenario, climate model, and probability distribution function), is propagated through a surrogate hydrodynamic/hydrologic model developed based on a physical 2D model. The results obtained from this study challenge the use of deterministic flood maps and recommend using probabilistic approaches for developing safe and reliable flood maps. Furthermore, they show that the main source of uncertainty comes from the precipitation, namely the selected probability distribution compared to the selected RCP and climate model.publishedVersio

An integrated simulation method for flash-flood risk assessment: 1. Frequency predictions in the Bisagno River by combining stochastic and deterministic methods

International audienceA stochastic rainfall generator and a deterministic rainfall-runoff model, both distributed in space and time, are combined to provide accurate flood frequency prediction in the Bisagno River basin (Thyrrenian Liguria, N.W. Italy). The inadequacy of streamflow records with respect to the return period of the required flow discharges makes the stochastic simulation methodology a useful operational alternative to a regionalisation procedure for flood frequency analysis and derived distribution techniques. The rainfall generator is the Generalized Neyman-Scott Rectangular Pulses (GNSRP) model. The rainfall-runoff model is the FEST98 model. The GNSRP generator was calibrated using a continuous 7-years' record of hourly precipitation measurements at five raingauges scattered over the Bisagno basin. The calibrated rainfall model was then used to generate a 1000 years' series of continuous rainfall data at the gauging sites and a flood-oriented model validation procedure was developed to evaluate the agreement between observed and simulated extreme values of rainfall at different scales of temporal aggregation. The synthetic precipitation series were input to the FEST98 model to provide flood hydrographs at selected cross-sections across the river network. Flood frequency analysis of the annual flood series (AFS) obtained from these simulations was undertaken using L-moment estimations of Generalized Extreme Value (GEV) distributions. The results are compared with those determined by applying a regional flood analysis in Thyrrhenian Liguria and the derived distribution techniques to the Bisagno river basin. This approach is also useful to assess the effects of changes in land use on flood frequency regime (see Rosso and Rulli, 2002). Keywords: flood frequency, stochastic rainfall generator, distributed rainfall runoff model, derived distributio

How land use/land cover changes can affect water, flooding and sedimentation in a tropical watershed: a case study using distributed modeling in the Upper Citarum watershed, Indonesia

[EN] Human activity has produced severe LULC changes within the Upper Citarum watershed and these changes are predicted to continue in the future. With an increase in population parallel to a 141% increment in urban areas, a reduction of rice fields and the replacement of forests with cultivations have been found in the past. Accordingly, LCM model was used to forecast the LULC in 2029. A distributed model called TETIS was implemented in the Upper Citarum watershed to assess the impact of the different historical and future LULC scenarios on its water and sediment cycles. This model was calibrated and validated with different LULCs. For the implementation of the sediment sub-model, it was crucial to use the bathymetric information of the reservoir located at the catchment's outlet. Deforestation and urbanization have been shown to be the most influential factors affecting the alteration of the hydrological and sedimentological processes in the Upper Citarum watershed. The change of LULC decreases evapotranspiration and as a direct consequence, the water yield increased by 15% and 40% during the periods 1994-2014 and 2014-2029, respectively. These increments are caused by the rise of three components in the runoff: overland flow, interflow and base flow. Apart from that, these changes in LULC increased the area of non-tolerable erosion from 412 km(2) in 1994 to 499 km(2) in 2029. The mean sediment yield increased from 3.1 Mton -yr(-1) in the 1994 LULC scenario to 6.7 Mton-yr(-1) in the 2029 LULC scenario. An increment of this magnitude will be catastrophic for the operation of the Saguling Dam.This study was partially funded by the Spanish Ministry of Economy and Competitiveness through the research projects TETISMED (CGL2014-58,127-C3-3-R) and TETISCHANGE (RTI2018-093717-B-I00). The authors are also thankful to the Directorate General of Higher Education of Indonesia (DIKTI) for the Ph.D. funding of the first author.Siswanto, SY.; Francés, F. (2019). How land use/land cover changes can affect water, flooding and sedimentation in a tropical watershed: a case study using distributed modeling in the Upper Citarum watershed, Indonesia. Environmental Earth Sciences. 78(17):1-15. https://doi.org/10.1007/s12665-019-8561-0S115781

Flood frequency analysis : a case study for the Brisbane River catchment

Flood is the most common natural hazards around the globe that has notable negative effects on humans and environment. One of the examples is Queensland 2010-2011 flood, which is considered as one of the severest floods in recent history of Australia that claimed 31 human lives and caused direct damage costing over $5 billion. To reduce the flood damage, it is vital to understand properly the causes of major floods, their magnitudes and frequencies. Estimation of the magnitude of possible future floods (also called design floods) is an important task in hydrology. Most of the hydraulic structures and flood management tasks require an accurate estimation of design floods. For this reason, estimation of design flood is still an area of great interest in flood hydrology and is being researched worldwide. Frequent devastating floods in Australia have drawn attention at the state and national levels for more accurate flood estimation with reduced uncertainty. Many design floods estimation methods are being practiced around the world. This study focuses on the widely used design flood estimate techniques called “flood frequency analysis (FFA)”. The main objective of FFA is to find probability distribution model that best fits the measured flood data series at a given site. Although Australian Rainfall and Runoff ARR (Australian Rainfall and Runoff), 1987 recommended Log Pearson type III probability distribution to use for FFA in Australia, in ARR 2019, no specific probability distribution is recommended. There has been limited guideline in Australia to select probability distribution models for flood frequency analysis. Also, many users have limited understanding on the uncertainties involved in design flood estimates based on a given probability distribution. This study is devoted to fill this research gap and examines the selection of the most appropriate probability distributions and associated uncertainty in FFA. This study focuses on the Brisbane River catchment of Queensland, one of the worst flood-prone areas in Australia. In this research, a total of 26 streamflow gauging stations are selected from the Brisbane River catchment, with the lengths of recorded annual maximum flood (AMF) data series in the range of 20 years to 91 years