date: 2015-10-01T10:26:27Z
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pdf:docinfo:title: Climate or Land Use??Attribution of Changes in River Flooding in the Sahel Zone
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dc:description: 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 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.

Keywords: simulation-based attribution; Sahel; Niger River; climate variability; hydrological modeling; flood mitigation; flood adaptation
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subject: 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 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.

dc:creator: Valentin Aich, Stefan Liersch, Tobias Vetter, Jafet C. M. Andersson, Eva N. Müller and Fred F. Hattermann
description: 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 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.

dcterms:created: 2015-06-12T10:16:06Z
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title: Climate or Land Use??Attribution of Changes in River Flooding in the Sahel Zone
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pdf:docinfo:keywords: simulation-based attribution; Sahel; Niger River; climate variability; hydrological modeling; flood mitigation; flood adaptation
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dc:title: Climate or Land Use??Attribution of Changes in River Flooding in the Sahel Zone
modified: 2015-10-01T10:26:27Z
cp:subject: 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 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.

pdf:docinfo:subject: 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 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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pdf:docinfo:creator: Valentin Aich, Stefan Liersch, Tobias Vetter, Jafet C. M. Andersson, Eva N. Müller and Fred F. Hattermann
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creator: Valentin Aich, Stefan Liersch, Tobias Vetter, Jafet C. M. Andersson, Eva N. Müller and Fred F. Hattermann
meta:author: Valentin Aich, Stefan Liersch, Tobias Vetter, Jafet C. M. Andersson, Eva N. Müller and Fred F. Hattermann
dc:subject: simulation-based attribution; Sahel; Niger River; climate variability; hydrological modeling; flood mitigation; flood adaptation
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