WADI (Arabic : وادي, translit. wādī, Hebrew : ואדי vādī)" is the Arabic and Hebrew term traditionally referring to a valley . In some instances, it may refer to a dry (ephemeral ) riverbed that contains water only during times of heavy rain .
* 1 Etymology * 2 General morphology and processes * 3 Sediments and sedimentary structures
* 4 Hydrological action
* 4.1 Deposits
* 5 See also
* 6 References
* 6.1 Bibliography
* 7 External links
The term wādī is very widely found in Arabic toponyms .
Some Spanish toponyms are derived from
GENERAL MORPHOLOGY AND PROCESSES
Wadis are located on the gently sloping, nearly flat parts of
deserts; commonly they begin on the distal portions of fans and extend
to inland sabkhas or playas . In basin and range topography , wadis
trend along basin axes at the terminus of fans. Permanent channels do
not exist, due to lack of continual water flow.
Wind also plays its role in deposition. When wadi sediments are underwater or moist, wind sediments are deposited over them. Thus wadi sediments contain both wind and water sediments.
SEDIMENTS AND SEDIMENTARY STRUCTURES
Flash floods represents severe energy conditions and results in wide
range of sedimentary structures, including ripples and commonly plane
beds. Gravels common display imbrications, Mud drapes show desiccation
cracks. Wind activity also generates its own sedimentary structures,
large scales cross-stratification and wedge shape cross-sets are
present. Typical wadi sequence consists of alternating units of wind
and water sediments; each unit range about 10–30 cm. Water laid
sediments show complete fining upward sequence. Gravels show
imbrication. Wind deposits are cross stratified and covered with
mud-cracked deposits. Some horizontal
Modern English usage differentiates a wadi from another canyon or wash by the action and prevalence of water. Wadis, as drainage courses, are formed by water, but are distinguished from river valleys or gullies in that surface water is intermittent or ephemeral. Wadis are generally dry year round, except after a rain. The desert environment is characterized by sudden but infrequent heavy rainfall, often resulting in flash floods . Crossing wadis at certain times of the year can be dangerous as a result.
Wadis tend to be associated with centers of human population because
sub-surface water is sometimes available in them. Nomadic and pastoral
desert peoples will rely on seasonal vegetation found in wadis, even
in regions as dry as the
The centrality of wadis to water — and human life — in desert environments gave birth to the distinct sub-field of wadi hydrology in the 1990s.
Triassic wadi deposit near Ogmore-By-Sea, Wales. Clasts are
Deposition in a wadi is rapid because of the sudden loss of stream
velocity and seepage of water into the porous sediment.
Over time, wadi deposits may become "Inverted Wadis" where the presence at one time of underground water caused vegetation and sediment to fill in the wadi's eroded channel, to the point that previous washes appear as ridges running through desert regions.
* ^ Ayuntamiento de Guadalajara, Guadalajara tourist guide, p.5.,
retrieved 17 August 2013
* ^ Review of Wheater, Howard ; Al Weshah, Radwan, Hydrology of
* Summary: Drainage Courses, Wadis. United States Army Corps of Engineers. Desert Processes Working Group; Knowledge Sciences, Inc. (n.d), retrieved 2008-08-26. * Summary: Summary: Drainage Courses, Wadis - Inverted. United States Army Corps of Engineers. Desert Processes Working Group; Knowledge Sciences, Inc. (n.d), retrieved 2008-08-2onments * Gelennie, K. W., 1970 Deserts sedimentary Environments. Developments in Sedimentology, v.14. Elsevier, Amsterdam, 222p.