![]() ![]() In Ethiopia, the 2016 flood event occurred with heavy Kiremt rains and caused many localized flash floods, landslides, and overflowing of rivers in Lower Omo Valley, Dire Dawa, Amhara, Afar, Somali, Tigray, Gambella, Oromia, and Harari regions. Commonly, these La Niήa events in Ethiopia were preceded by the drought effects of El Niήo events.ĭuring 2016 some areas in the Horn of Africa experienced flood events following the 2015 El Niήo (drought) events. The identified historical flood event years (1988, 1996, 1998, 2006, 2010, 2012, and 2016) in the country were also known as La Niήa episodes. Evidences indicated that in past few decades, many flooding events occurred during La Niήa climate conditions. ![]() Rainfall increase during La Niήa events in the Blue Nile Basin is reported ( Abtew et al., 2009). Forecasts of National Meteorological Agency of Ethiopia (NMA) report that most Kiremt rain (summer rain) benefiting areas of the country with above normal rainfall are increasing chances of flooding.Ĭommonly, La Niήa episodes are associated with heavier than normal rains during June to September long rains in central and highland areas of Ethiopia causing flooding. Changes in heavy precipitation intensities have been attributed to floods ( Zhang et al., 2007). Scientific studies and climate model projections show that climate change will increase the incidence of heavy rainstorms which puts many communities to frequent flood risks. Many studies on climate extreme impacts such as heat waves, droughts, floods, and wildfires expose significant vulnerability and exposure to the human environment and socioeconomic systems ( IPCC, 2012). Climate change impact on hydrologic processes will influence flooding extent and characteristics ( Conway, 2000 Alemu and Dagnachew, 2011). Changes in catchment surface characteristics as land cover, floodplain storage, and urbanization can modify the characteristics of river floods requiring planning and flood management for sustainable development ( Guan et al., 2011 Baulies and Szejwach, 1998). The nature of hydrological systems such as catchment size, landscape cover, topography, and soils determines flood risks. Precipitation, antecedent soil moisture content, surface water levels, reservoir, and drainage management decisions determine the scale of flooding. The characteristics of intense precipitation amount and distribution and the antecedent conditions of hydrological variables (soil moisture content, groundwater, and surface water levels) play a significant role in physically modifying flood affecting factors ( Guan et al., 2011). The flood flow conditions in many river systems are most likely affected by climate-related impacts and anthropogenic activities. Melesse, in Extreme Hydrology and Climate Variability, 2019 29.4 State of flood events The plume extension is especially large from November to February, although it does not necessarily follow the river discharge, especially during the spring months when winds tend to dilute the plume ( Costoya et al., 2016). (2004), Charria, Lamouroux, and De Mey (2016), Alvera-Azcárate, Barth, Parard, and Beckers (2016), and Costoya et al. González-Nuevo and Nogueira (2014) studied the Cantabrian plumes using in situ data and the plumes of Loire and Garonne were analyzed by Puillat et al. River plumes have been analyzed during the past few years. Adour is an intermediate river with a mean runoff on the order of 350 m 3 s − 1 and with an annual cycle similar to Loire and Garonne. Their mean discharge is on the order of 900 m 3 s − 1 with a marked annual cycle, reaching mean maximum values higher than 1200 m 3 s − 1 in January and mean minimum values lower than 500 m 3 s − 1 in August. Loire and Gironde are the two main rivers in the Bay of Biscay, providing around 80% of the freshwater discharge onto the French shelf. These together supply a mean freshwater discharge of 400 m 3 s − 1. Rivers in the Cantabrian shelf are short and flow swiftly, although with a small runoff due to the proximity of mountain ranges to the coast. River discharge is the main source of freshwater flowing into the Bay of Biscay. Luis Valdés, in World Seas: an Environmental Evaluation (Second Edition), 2019 5.2.2.1 River Discharge ![]()
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