Department of Hydrology and Hydrodynamics IG PAS
https://dspace.igf.edu.pl/xmlui/handle/123456789/10
2024-03-13T23:02:46ZModelling the impact of historical and future Land Use Land Cover changes on the hydrological response of an Ethiopian watershed
https://dspace.igf.edu.pl/xmlui/handle/123456789/125
Modelling the impact of historical and future Land Use Land Cover changes on the hydrological response of an Ethiopian watershed
Regasa, Motuma Shiferaw; Nones, Michael
Land Use Land Cover (LULC) is generally considered one of the key factors influencing the hydrological processes and sediment output in arid and semi-arid watersheds. Focusing on the Ethiopian Fincha watershed, the current study applies the Soil & Water Assessment Tool (SWAT) model to evaluate how LULC changes affect the watershed hydrological dynamics. Utilizing the available stream flow time series data acquired from 1986 to 2008, the model was calibrated and validated based on past conditions. At the same time, future scenarios were simulated by means of the Land Change Modeler (LCM) model using historical trends. To investigate the effect of LULC changes on watershed hydrology, six LULC maps have been produced to account for historical (1989, 2004, 2019) and future (2030, 2040, 2050) conditions. The results show an increase in surface runoff in the past, while a similar tendency is expected for the next three decades if no specific mitigation measures will be implemented soon. On the other hand, lateral flow and
groundwater flow are generally decreasing. The present analysis shows that the ongoing LULC transformation, which involves an expansion of agricultural land, urban areas, and intermittent logging of forest cover, may be the reason for the increment in surface runoff, and the decline in groundwater and lateral flow.
2024-01-10T00:00:00ZCan sediments play a role in river flood risk mapping? Learning from selected European examples
https://dspace.igf.edu.pl/xmlui/handle/123456789/121
Can sediments play a role in river flood risk mapping? Learning from selected European examples
Nones, Michael; Guo, Yiwei
Background:
Climate change and increasing anthropogenic pressure are two of the major drivers of increasing extreme events like droughts and floods. To deal with the increasing number of flooding events hitting Europe in the last few decades, around twenty years ago the European Commission started to develop ad-hoc legislation to reduce flood risk by mapping flood hazard and risk areas, such as the Directive 2007/60/EC on the Assessment and Management of Flood Risk. This Directive looks to identify regions where flood management strategies should be prioritized. Despite this holistic approach, flaws connected to the consideration of sediment transport and morphological changes in rivers exist, leading to potential underestimations of the impact of floods affecting active watercourses or areas subjected to frequent morphological changes.
Results:
By discussing six examples related to European lowland and mountain watercourses affected by significant floods in the last 20 years, the present mini-review aims to provide additional evidence on the need for a rethinking of flood risk mapping, moving from a “clear water” perspective to a more integrated approach, where the interactions between all the fluvial components (water, sediment, biota, and humans) are adequately considered.
Conclusions:
The examples reported here show the importance of considering sediment and wood in flood risk management, suggesting the need for integrating flood-related studies with other disciplines like geomorphology and ecohydrology.
2023-09-28T00:00:00ZSWAT model-based quantification of the impact of land use land cover change on sediment yield in the Fincha watershed, Ethiopia
https://dspace.igf.edu.pl/xmlui/handle/123456789/120
SWAT model-based quantification of the impact of land use land cover change on sediment yield in the Fincha watershed, Ethiopia
Regasa, Motuma Shiferaw; Nones, Michael
In recent years, Ethiopia is facing problems due to soil erosion, mainly because of
the conversion of natural vegetation into cultivated land to answer to increasing
human pressure. Such changes in coverage are fostering soil erosion, which is also
affecting dam reservoirs, because of the increasing sediment yield entering the
lake. The present study focuses on the Ethiopian Fincha watershed and takes
advantage of the potentiality of the Soil and Water Assessment Tool (SWAT) model,
to investigate how land use land cover changes impact soil erosion and the
consequent sediment yield entering the Fincha Dam. The SWAT model was
calibrated and validated using time series data of stream flow and sediment
covering the period 1986-2008, and its performance was evaluated by looking
at the coefficient of determination, Nash-Sutcliffe simulation efficiency, and per
cent bias. Once validated, the SWAT model was applied to derive sediment yield
for the future 30 years, based on forecasted land use land cover conditions. The
results show that the mean annual soil loss rate increased from 32.51 t ha−1 in
1989 to 34.05 t ha−1 in 2004, reaching 41.20 t ha−1 in 2019. For the future, a higher
erosion risk should be expected, with the annual soil loss rate forecasted to be
46.20 t ha−1 in 2030, 51.19 t ha−1 in 2040, and 53.98 t ha−1 in 2050. This soil erosion
means that sediments transported to the Fincha Dam, located at the watershed
outlet, increased significantly in the last 30 years (from 1.44 in 1989 to 2.75 mil t in
2019) and will have the same trend in the future (3.08–4.42 mil t in 2020 and 2050,
respectively), therefore highly affecting the Fincha reservoir services in terms of
reduction of water volume for irrigation and hydroelectric power generation. By
providing possible medium/long-term scenarios, the present work can help land
planners and decision-makers in developing future land management strategies
based on actual projections, eventually aiming to reduce soil erosion at the
watershed scale and guarantee the sustainable development of the Fincha
region and its key hydraulic infrastructures.
2023-09-07T00:00:00ZSpatiotemporal variations of riverine flood fatalities: 70 years global to regional perspective
https://dspace.igf.edu.pl/xmlui/handle/123456789/115
Spatiotemporal variations of riverine flood fatalities: 70 years global to regional perspective
Hamidifar, Hossein; Nones, Michael
Floods are among the most devastating natural hazards worldwide. While rainfall is the primary trigger of floods, human activities and climate change can exacerbate the impacts of floods and lead to more significant economic and social consequences. In this research, fluvial flood fatalities in the 1951–2020 period have been studied, analyzing the information reported in the Emergency Database (EM‐DAT). The EM‐DAT data were classified into five categories in terms of the number of events and fatalities connected with riverine floods, considering only events that caused more than 10 fatalities. The results show that
the severity of flood‐related fatalities is not equally distributed worldwide, but presents specific geographical patterns. The flood fatality coefficient, which represents the ratio between the total number of fatalities and the number of flood events, calculated for different countries, identified that the Southern, Eastern, and South‐Eastern regions of Asia have the deadliest floods in the world. The number of flood events has been increasing since 1951 and peaked in 2007, following a relative decline since then. Though, the resulting fatalities do not follow a statistically significant trend. An analysis of the number of flood events in different decades shows that the 2001–2010 decade saw the highest number of events, which corresponds to the largest precipitation anomaly in the world. The lethality of riverine floods decreased over time, from 412 per flood in 1951–1960 to 67 in the 2011–2020 decade. This declining trend is probably a consequence of a more resilient environment and better risk reduction strategies. Based on the
presented data and using regression analysis, relationships between flood fatalities and the number of flood events with population density and gross domestic product are developed and discussed.
2023-05-14T00:00:00Z