Afedena is a river of the

Nile The Nile, , Bohairic , lg, Kiira , Nobiin language, Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered ...

basin. Rising in the mountains of Dogu’a Tembien in northern

Ethiopia Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...

, it flows southwestward to empty finally in

Giba Gilberto Amauri de Godoy Filho, known as Giba (born 23 December 1976), is a Brazilian former professional volleyball player who played as an outside hitter. For much of the 2000s, he was widely regarded as one of the best volleyball players in t ...

and

Tekezé River The Tekezé or Täkkäze River ( amh, ተከዜ, ti, ተከዘ; originally meaning "river" in Ge’ez, ), also spelled Takkaze, is a major river of Ethiopia. For part of its course it forms a section of the westernmost border of Ethiopia and Erit ...

Characteristics

It is a confined ephemeral river, locally

meander A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse erodes the sediments of an outer, concave bank ( cut bank) and deposits sediments on an inner, convex bank ...

ing in its narrow alluvial plain, with an average slope gradient of 35 metres per kilometre. With its tributaries, the river has cut a gorge.

Flash floods and flood buffering

Runoff mostly happens in the form of high runoff discharge events that occur in a very short period (called

flash floods A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice or snow flowing o ...

). These are related to the steep topography, often little vegetation cover and intense convective rainfall. The peaks of such flash floods have often a 50 to 100 times larger discharge than the preceding

baseflow Baseflow (also called drought flow, groundwater recession flow, low flow, low-water flow, low-water discharge and sustained or fair-weather runoff) is the portion of the streamflow that is sustained between precipitation events, fed to streams by d ...

. The magnitude of floods in this river has however been decreased due to interventions in the catchment. At Afedena,

exclosure An exclosure, in an area being used extensively for grazing, is a limited area from which unwanted browsing animals, such as domestic cattle or wildlife such as deer, are excluded by fencing or other means. Environmental protection Most commonl ...

s have been established; the dense vegetation largely contributes to enhanced

infiltration Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (me ...

, less flooding and better

. Physical conservation structures such as stone bunds and

check dam A steel check dam A check dam is a small, sometimes temporary, dam constructed across a swale, drainage ditch, or waterway to counteract erosion by reducing water flow velocity. Check dams themselves are not a type of new technology; rather, the ...

s also intercept runoff.

Boulders and pebbles in the river bed

Boulders and pebbles encountered in the river bed can originate from any location higher up in the catchment. In the uppermost stretches of the river, only rock fragments of the upper lithological units will be present in the river bed, whereas more downstream one may find a more comprehensive mix of all lithologies crossed by the river. From upstream to downstream, the following lithological units occur in the catchment. * Lower basalt *

Amba Aradam Formation The Amba Aradam Formation is a Cretaceous sandstone formation in Ethiopia. It is up to 200 metres thick, for instance in the Degua Tembien district. As fossils are absent, the age of the Amba Aradam Formation was interpreted based on the age of a ...

Antalo Limestone The Antalo Limestone, also known as the Antalo Sequence, is a geological formation in Ethiopia. It is between 300 and 800 metres thick and comprises fossiliferous limestones and marls that were deposited in a reef. Marine microfossils have shown a ...

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...

freshwater

tufa Tufa is a variety of limestone formed when carbonate minerals precipitate out of water in unheated rivers or lakes. Geothermally heated hot springs sometimes produce similar (but less porous) carbonate deposits, which are known as travertine. ...

References

{{reflist Rivers of Ethiopia Dogu'a Tembien Tigray Region Nile basin

Characteristics

Flash floods and flood buffering

Boulders and pebbles in the river bed

See also

References