HESS Opinions &amp;quot;More efforts and scientific rigour are needed to attribute trends in flood time series&amp;quot;

Merz, Bruno; Vorogushyn, Sergiy; Uhlemann, S.; Delgado, José Miguel; Hundecha, Yeshewatesfa

doi:10.5194/hessd-9-1345-2012

Cited by 24 publications

(35 citation statements)

References 47 publications

(54 reference statements)

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“…While this study focused on the influence of temperature and precipitation changes on the observed streamflow increase, rigorous trend attribution studies should also comprise a search for possible alternative drivers and evidence that these are inconsistent with the observed changes [Merz et al, 2012]. Such alternative drivers could be changes in other meteorological variables than temperature or precipitation, in water management, or in land cover.…”

Section: Drivers Included In the Attributionmentioning

confidence: 99%

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Attribution of streamflow trends in snow and glacier melt‐dominated catchments of the Tarim River, Central Asia

Duethmann

Bolch

Farinotti

et al. 2015

Water Resources Research

172

142

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Observed streamflow of headwater catchments of the Tarim River (Central Asia) increased by about 30% over the period . This study aims at assessing to which extent these streamflow trends can be attributed to changes in air temperature or precipitation. The analysis includes a data-based approach using multiple linear regression and a simulation-based approach using a hydrological model. The hydrological model considers changes in both glacier area and surface elevation. It was calibrated using a multiobjective optimization algorithm with calibration criteria based on glacier mass balance and daily and interannual variations of discharge. The individual contributions to the overall streamflow trends from changes in glacier geometry, temperature, and precipitation were assessed using simulation experiments with a constant glacier geometry and with detrended temperature and precipitation time series. The results showed that the observed changes in streamflow were consistent with the changes in temperature and precipitation. In the Sari-Djaz catchment, increasing temperatures and related increase of glacier melt were identified as the dominant driver, while in the Kakshaal catchment, both increasing temperatures and increasing precipitation played a major role. Comparing the two approaches, an advantage of the simulation-based approach is the fact that it is based on process-based relationships implemented in the hydrological model instead of statistical links in the regression model. However, data-based approaches are less affected by model parameter and structural uncertainties and typically fast to apply. A complementary application of both approaches is recommended.

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Section: Drivers Included In the Attributionmentioning

confidence: 99%

“…The link between trends in streamflow and possible climatic drivers may be investigated by data-based or simulation-based approaches [Merz et al, 2012]. Data-based approaches directly relate changes in runoff to changes in climate without the additional step of applying a hydrological model.…”

Section: Introductionmentioning

confidence: 99%

Attribution of streamflow trends in snow and glacier melt‐dominated catchments of the Tarim River, Central Asia

Duethmann

Bolch

Farinotti

et al. 2015

Water Resources Research

172

142

View full text Add to dashboard Cite

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“…There are studies, which distinguish climate change and LULC impacts on historical trends in flood magnitude, but not systematically and within one modeling approach (e.g., [17]). To the best of our knowledge, the only study published which follows the protocol of Merz et al (2012) [5] is that by Hundecha and Merz (2012) [18]. Hundecha and Merz (2012) [18] drove a hydrological model with a large number of stationary and non-stationary climate time series in order to study whether the observed flood trend was climate driven.…”

Section: Introductionmentioning

confidence: 99%

“…The specific research question is, to which share LULC and/or climatic changes cause the increase of river flooding in the area. To this end, a simulation-based attribution approach proposed by Merz et al (2012) [5] is used. Merz et al (2012) [5] introduced a hypothesis testing framework for attributing changes of flood regime, which is based on testing the consistency or inconsistency of plausible drivers with the observed flood trend and providing a confidence level for the attribution.…”

Section: Introductionmentioning

confidence: 99%

Climate or Land Use?—Attribution of Changes in River Flooding in the Sahel Zone

Aich

Liersch

Vetter

et al. 2015

Water

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This study intends to contribute to the ongoing discussion on whether land use and land cover changes (LULC) or climate trends have the major influence on the observed increase of flood magnitudes in the Sahel. A simulation-based approach is used for attributing the observed trends to the postulated drivers. For this purpose, the ecohydrological model SWIM (Soil and Water Integrated Model) with a new, dynamic LULC module was set up for the Sahelian part of the Niger River until Niamey, including the main tributaries Sirba and Goroul. The model was driven with observed, reanalyzed climate and LULC data for the years 1950-2009. In order to quantify the shares of influence, one simulation was carried out with constant land cover as of 1950, and one including LULC. As quantitative measure, the gradients of the simulated trends were compared to the observed trend. The modeling studies showed that for the Sirba River only the simulation which included LULC was able to reproduce the observed trend. The simulation without LULC showed a positive trend for flood magnitudes, but underestimated the trend significantly. For the Goroul River and the local flood of the Niger River at Niamey, the simulations were only partly able to reproduce the observed trend. In conclusion, the new LULC module OPEN ACCESSWater 2015, 7 2797 enabled some first quantitative insights into the relative influence of LULC and climatic changes. For the Sirba catchment, the results imply that LULC and climatic changes contribute in roughly equal shares to the observed increase in flooding. For the other parts of the subcatchment, the results are less clear but show, that climatic changes and LULC are drivers for the flood increase; however their shares cannot be quantified. Based on these modeling results, we argue for a two-pillar adaptation strategy to reduce current and future flood risk: Flood mitigation for reducing LULC-induced flood increase, and flood adaptation for a general reduction of flood vulnerability.

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“…To better understand, analyze and model urban hydrology, as urbanization progression in West Africa is also the highest in the world, mostly due to the low current urbanization rate; • To improve the knowledge of the role of imperviousness and of drainage system; • To implement adapted hydrological modelling accounting for these processes and adopting rigorous statistical attribution approaches, as suggested, e.g., by Merz et al (2012) [119].…”

mentioning

confidence: 99%

Evolution of Surface Hydrology in the Sahelo-Sudanian Strip: An Updated Review

Descroix

Guichard

Grippa

et al. 2018

Water

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Abstract:In the West African Sahel, two paradoxical hydrological behaviors have occurred during the last five decades. The first paradox was observed during the 1968-1990s 'Great Drought' period, during which runoff significantly increased. The second paradox appeared during the subsequent period of rainfall recovery (i.e., since the 1990s), during which the runoff coefficient continued to increase despite the general re-greening of the Sahel. This paper reviews and synthesizes the literature on the drivers of these paradoxical behaviors, focusing on recent works in the West African Sahelo/Sudanian strip, and upscaling the hydrological processes through an analysis of recent data from two representative areas of this region. This paper helps better determine the respective roles played by Land Use/Land Cover Changes (LULCC), the evolution of rainfall intensity and the occurrence of extreme rainfall events in these hydrological paradoxes. Both the literature review and recent data converge in indicating that the first Sahelian hydrological paradox was mostly driven by LULCC, while the second paradox has been caused by both LULCC and climate evolution, mainly the recent increase in rainfall intensity.

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HESS Opinions "More efforts and scientific rigour are needed to attribute trends in flood time series"

Cited by 24 publications

References 47 publications

Attribution of streamflow trends in snow and glacier melt‐dominated catchments of the Tarim River, Central Asia

Attribution of streamflow trends in snow and glacier melt‐dominated catchments of the Tarim River, Central Asia

Climate or Land Use?—Attribution of Changes in River Flooding in the Sahel Zone

Evolution of Surface Hydrology in the Sahelo-Sudanian Strip: An Updated Review

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