Detection and attribution of flood trends in Mediterranean basins

Tramblay, Yves; Mimeau, Louise; Neppel, Luc; Vinet, Freddy; Sauquet, Éric

doi:10.5194/hess-23-4419-2019

Cited by 59 publications

(52 citation statements)

References 76 publications

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“…This is attributable to other factors which modulate flood response, such as initial soil moisture. For example, Tramblay et al (2019) found that, despite the increase in extreme precipitation, the fewer detected annual occurrences of extreme floods in 171 Mediterranean basins were likely caused by decreasing soil moisture. The relationship between the flow rate and the initial saturation state of the soil is often non-linear, and the effect of antecedent soil moisture strongly depends on soil type and geology.…”

Section: Introductionmentioning

confidence: 99%

Do small and large floods have the same drivers of change? A regional attribution analysis in Europe

Bertola

Viglione

Vorogushyn

et al. 2021

Hydrol. Earth Syst. Sci.

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Abstract. Recent studies have shown evidence of increasing and decreasing trends for average floods and flood quantiles across Europe. Studies attributing observed changes in flood peaks to their drivers have mostly focused on the average flood behaviour, without distinguishing small and large floods. This paper proposes a new framework for attributing flood changes to potential drivers, as a function of return period (T), in a regional context. We assume flood peaks to follow a non-stationary regional Gumbel distribution, where the median flood and the 100-year growth factor are used as parameters. They are allowed to vary in time and between catchments as a function of the drivers quantified by covariates. The elasticities of floods with respect to the drivers and the contributions of the drivers to flood changes are estimated by Bayesian inference. The prior distributions of the elasticities of flood quantiles to the drivers are estimated by hydrological reasoning and from the literature. The attribution model is applied to European flood and covariate data and aims at attributing the observed flood trend patterns to specific drivers for different return periods at the regional scale. We analyse flood discharge records from 2370 hydrometric stations in Europe over the period 1960–2010. Extreme precipitation, antecedent soil moisture and snowmelt are the potential drivers of flood change considered in this study. Results show that, in northwestern Europe, extreme precipitation mainly contributes to changes in both the median (q2) and 100-year flood (q100), while the contributions of antecedent soil moisture are of secondary importance. In southern Europe, both antecedent soil moisture and extreme precipitation contribute to flood changes, and their relative importance depends on the return period. Antecedent soil moisture is the main contributor to changes in q2, while the contributions of the two drivers to changes in larger floods (T>10 years) are comparable. In eastern Europe, snowmelt drives changes in both q2 and q100.

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Section: Introductionmentioning

confidence: 99%

Do small and large floods have the same drivers of change? A regional attribution analysis in Europe

Bertola

Viglione

Vorogushyn

et al. 2021

Hydrol. Earth Syst. Sci.

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“…The water contained in the unsaturated, or vadose zone, is an important driver for floods with soils close to saturation having more probability to produce runoff when subjected to precipitation inputs (Zehe et al, 2005;Ivancic and Shaw, 2015;Woldemeskel and Sharma, 2016;Bennett et al, 2018;Wasko and Nathan, 2019). This is particularly true in the Mediterranean context where several studies have shown the strong influence of soil moisture on flood generation processes (Brocca et al, 2008;Penna et al, 2011;Tramblay et al, 2010Tramblay et al, , 2019Uber et al, 2018). Similarly, Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

“…There is a climatic trend towards a drying of the Mediterranean region, both during the historical period but also in future climate scenarios, showing a decrease in precipitation amounts and occurrence, associated with an increasing frequency of drought episodes (Hoerling et al, 2012;Polade et al, 2014Polade et al, , 2017Hertig and Tramblay, 2017;Lionello and Scarascia, 2018;Tramblay et al, 2020). For a RCP8.5 emission scenario, Giannakopoulos et al (2009) and Polade et al (2014) both estimate a mean decrease up to −30 % of the annual precipitation in the Mediterranean region by the end of the century and an increase of dry days ranging between +1 to +3 weeks per year.…”

Section: Introductionmentioning

confidence: 99%

Modeling the response of soil moisture to climate variability in the Mediterranean region

Mimeau

Tramblay

Brocca

et al. 2021

Hydrol. Earth Syst. Sci.

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Abstract. Future climate scenarios for the Mediterranean region indicate a possible decrease in annual precipitation associated with an intensification of extreme rainfall events in the coming years. A major challenge in this region is to evaluate the impacts of changing precipitation patterns on extreme hydrological events such as droughts and floods. For this, it is important to understand the impact of climate change on soil moisture since it is a proxy for agricultural droughts, and the antecedent soil moisture condition plays a key role on runoff generation. This study focuses on 10 sites, located in southern France, with available soil moisture, temperature, and precipitation observations for a 10-year time period. Soil moisture is simulated at each site at the hourly time step using a model of soil water content. The sensitivity of the simulated soil moisture to different changes in precipitation and temperature is evaluated by simulating the soil moisture response to temperature and precipitation scenarios generated using a delta change method for temperature and a stochastic model (the Neyman–Scott rectangular pulse model) for precipitation. Results show that soil moisture is more impacted by changes in precipitation intermittence than precipitation intensity and temperature. Overall, increased temperature and precipitation intensity associated with more intermittent precipitation leads to decreased soil moisture and an increase in the annual number of days with dry soil moisture conditions. In particular, a temperature increase of +4 ∘C combined with a decrease of annual rainfall between 10 % and 20 %, corresponding to the current available climate scenarios for the Mediterranean, lead to a lengthening of the drought period from June to October with an average of +28 d of soil moisture drought per year.

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“…For instance, initial soil moisture conditions prior to flood events play a key role in causing floods. An increase in rainfall intensity does not necessarily result in an increased flood risk because the runoff coefficient can be very variable over time and space due to complex interactions between precipitation and infiltration processes (Tramblay et al, 2019). The type of soil can also have different sensitivity to changing climatic conditions (Camici et al, 2017;Piras et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Floods evolution in the Mediterranean region in a context of climate and environmental change

Llasat

2021

CIG

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Floods are the most important risk in the Mediterranean region, both due to their frequency and impact. Studies of historical floods show flood-rich periods that could be associated with climate causes, but there is also a certain growing trend as a result of changes in land use and increased vulnerability. If climate scenarios point to an increase in the torrentiality of precipitation, with longer dry periods and more intense rainfall, there is still a high level of uncertainty in their impact in floods. This paper addresses this issue, also considering the complex role of changes to hazards, vulnerability, exposure and capacity. It presents a synthesis of the state of the art, with particular incidence in the first results of MedECC and the most recent bibliography on floods trend. Conclusions show that floods in this region are mainly consequence of flash-flood events. A common positive trend of flash floods in the past probably due to land use changes and the occupation of flood-prone areas has been found (high confidence). The increase of convective precipitation could also justify this positive trend in the most recent period, in some regions (low confidence). Vulnerabilities to water related hazards are expected to be influenced by the future socio-economic conditions at the regional scale (medium confidence). Although expected changes in flood risks are not univocal, nor evenly distributed, flood impacts will increase in the entire Mediterranean region, mainly as a consequence of global changes in the catchments (land use, vulnerability, exposure), joined in the Northern part of the basin to the increase of heavy rainfalls (medium confidence).

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Detection and attribution of flood trends in Mediterranean basins

Cited by 59 publications

References 76 publications

Do small and large floods have the same drivers of change? A regional attribution analysis in Europe

Do small and large floods have the same drivers of change? A regional attribution analysis in Europe

Modeling the response of soil moisture to climate variability in the Mediterranean region

Floods evolution in the Mediterranean region in a context of climate and environmental change

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