The Adawro is a torrent of the

Nile The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...

basin. Rising on the Ts’ats’en plateau of Dogu’a Tembien in northern

Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...

, it flows northward to empty finally in the

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 playe ...

and

Tekezé River The Tekezé River (; , originally meaning "river" in Ge’ez; , also spelled Takkaze; ), is a major river in Ethiopia. For part of its course it forms a section of the westernmost border of Ethiopia and Eritrea. The river is also known as the Seti ...

Characteristics

The Adawro is a confined bedrock river, with an average slope gradient of 117 metres per kilometre. The river has cut a gorge in the surrounding basalt. Adawro

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 and snow. Flash fl ...

). 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, including the establishment of the Adawro exclosure on the upper slopes of the catchment. 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, t ...

s also intercept runoff. Log dam in Adawro river

Observing that, in rivers with coarse

bedload The term bed load or bedload describes particles in a flowing fluid (usually water) that are transported along the stream bed. Bed load is complementary to suspended load and wash load. Bed load moves by rolling, sliding, and/or saltating (hop ...

gabion A gabion (from Italian ''gabbione'' meaning "big cage"; from Italian ''gabbia'' and Latin ''cavea'' meaning "cage") is a cage, cylinder or box filled with rocks, concrete, or sometimes sand and soil for use in civil engineering, road building ...

s were destroyed by abrasion, boulder-faced log dams were installed transversally across this torrent. They were embedded in the banks of torrent, 0.5–1 m above the bed, and their upstream sides were faced with large rocks. Such dams lead to temporary water ponding, spreading of peak flow over the entire channel width, and sediment deposition. After testing under extreme flow conditions (including two heavy storms) it appeared that 60% of the dams resisted strong floods, particularly in the upper segment of the river. Neighbouring farmers appreciate such structures to control first-order torrents with coarse bed load because the technique is cheap and can be easily installed. Adawro river

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. * Upper basalt * Interbedded lacustrine deposits * Lower basalt * Amba Aradam Formation DT drainage

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