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25-540: Wadi Harrana is a seasonal stream ( wadi ) in the eastern Jordanian Badia , about sixty kilometers southeast of the city of Amman . It runs eastwards from the edge of the Jordanian Highlands to the Azraq oasis . Harrana's climate , much like most of Jordan, is influenced by the moderate Mediterranean climate from the west, the very hot Sahara 's climate from the east, and the cold European climate from

50-491: 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 Sahara , as they travel in complex transhumance routes. The centrality of wadis to water – and human life – in desert environments gave birth to the distinct sub-field of wadi hydrology in

75-412: A significant hazard, causing more fatalities in the U.S. in an average year than lightning, tornadoes , or hurricanes . They can also deposit large quantities of sediments on floodplains and destroy vegetation cover not adapted to frequent flood conditions. Flash floods most often occur in dry areas that have recently received precipitation , but they may be seen anywhere downstream from the source of

100-427: A storm that occurs on a mesa miles away. The flood sweeps through the canyon; the canyon makes it difficult to climb up and out of the way to avoid the flood. For example, a cloudburst in southern Utah on 14 September 2015 resulted in 20 flash flood fatalities, of which seven fatalities occurred at Zion National Park when hikers were trapped by floodwaters in a slot canyon. Flash floods induce severe impacts in both

125-447: A very short time. Second, these rains often fall on poorly absorbent and often clay-like soil, which greatly increases the amount of runoff that rivers and other water channels have to handle. These regions tend not to have the infrastructure that wetter regions have to divert water from structures and roads, such as storm drains, culverts, and retention basins , either because of sparse population or poverty, or because residents believe

150-709: A wide range of sedimentary structures, including ripples and common plane beds. Gravels commonly display imbrications , and mud drapes show desiccation cracks. Wind activity also generates sedimentary structures, including large-scale cross-stratification and wedge-shaped cross-sets. A typical wadi sequence consists of alternating units of wind and water sediments; each unit ranging from about 10–30 cm (4–12 in). Sediment laid by water shows complete fining upward sequence. Gravels show imbrication. Wind deposits are cross-stratified and covered with mud-cracked deposits. Some horizontal loess may also be present. Modern English usage differentiates wadis from canyons or washes by

175-432: Is enough to carry away most SUV-sized vehicles. The U.S. National Weather Service reported in 2005 that, using a national 30-year average, more people die yearly in floods, 127 on average, than by lightning (73), tornadoes (65), or hurricanes (16). In deserts , flash floods can be particularly deadly for several reasons. First, storms in arid regions are infrequent, but they can deliver an enormous amount of water in

200-504: Is the Arabic term traditionally referring to a river valley . In some instances, it may refer to a wet ( ephemeral ) riverbed that contains water only when heavy rain occurs. Arroyo ( Spanish ) is used in the Americas for similar landforms. The term wādī is very widely found in Arabic toponyms . Some Spanish toponyms are derived from Andalusian Arabic where wādī

225-556: The Muwaqqar Chalk Marl Formation of Harrana The best preserved and complete specimens of the extinct teleostean fish genus Saurocephalus and the most complete mosasaur Carinodens remains come from the latest Maastrichtian of Harrana. Wadi Wadi ( Arabic : وَادِي , romanized :  wādī , alternatively wād ; Arabic : وَاد , Maghrebi Arabic oued , Hebrew : וָאדִי , romanized :  vadi , lit.   'wadi')

250-509: The 1990s. Deposition in a wadi is rapid because of the sudden loss of stream velocity and seepage of water into the porous sediment. Wadi deposits are thus usually mixed gravels and sands. These sediments are often altered by eolian processes. Over time, wadi deposits may become "inverted wadis," where former underground water caused vegetation and sediment to fill in the eroded channel, turning previous washes into ridges running through desert regions. Flash flood Flash floods are

275-479: The U.S. National Weather Service (NWS) Storm Data datasets to connect the impact of flash floods with the physical processes involved in flash flooding. This should increase the reliability of flash flood impact forecasting models. Analysis of flash floods in the United States between 2006 and 2012 shows that injuries and fatalities are most likely in small, rural catchments, that the shortest events are also

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300-425: 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

325-479: The built and the natural environment. The effects of flash floods can be catastrophic and show extensive diversity, ranging from damages in buildings and infrastructure to impacts on vegetation, human lives and livestock. The effects are particularly difficult to characterize in urban areas. Researchers have used datasets such as the Severe Hazards Analysis and Verification Experiment (SHAVE) and

350-439: The dangers of flash floods. What makes flash floods most dangerous is their sudden nature and fast-moving water. A vehicle provides little to no protection against being swept away; it may make people overconfident and less likely to avoid the flash flood. More than half of the fatalities attributed to flash floods are people swept away in vehicles when trying to cross flooded intersections. As little as 2 feet (0.61 m) of water

375-504: The distal portions of alluvial fans and extend to inland sabkhas or dry lakes . 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. They have braided stream patterns because of the deficiency of water and the abundance of sediments . Water percolates down into the stream bed, causing an abrupt loss of energy and resulting in vast deposition. Wadis may develop dams of sediment that change

400-531: The end of spring and beginning of summer. Harrana is significant for its fossil deposits preserved in gigantic limestone concretions that date back to the latest Maastrichtian some 66–67 million years ago, a period notably close to the end-Cretaceous extinction events when many groups of animals such as dinosaurs and as much as 65–70% of all marine animal species became extinct. Mosasaur specimens along with their remarkably well preserved scale imprints have been discovered from late Maastrichtian deposits of

425-432: The flood effects are grouped into 4 categories: (i) impacts on built environment (ii) impacts on man-made mobile objects,(iii) impacts on the natural environment (including vegetation, agriculture, geomorphology, and pollution) and (iv) impacts on the human population (entrapments, injuries, fatalities). The scale was proposed as a tool on prevention planning, as the resulting maps offer insights on future impacts, highlighting

450-643: The high severity areas. Flash floods can cause rapid soil erosion. Much of the Nile delta sedimentation may come from flash flooding in the desert areas that drain into the Nile River . However, flash floods of short duration produce relatively little bedrock erosion or channel widening, having their greatest impact from sedimentation on the floodplain. Some wetlands plants, such as certain varieties of rice, are adapted to endure flash flooding. However, plants that thrive in drier areas can be harmed by flooding, as

475-414: The most dangerous, that the hazards are greatest after nightfall, and that a very high fraction of injuries and fatalities involve vehicles. An impact severity scale is proposed in 2020 providing a coherent overview of the flash flood effects through the classification of impact types and severity and mapping their spatial extent in a continuous way across the floodplain. Depending on the affected elements,

500-496: The north. Though arid, the area is rich in animal life. Birds, owls, rodents, rabbits, foxes, occasional wolves and hyenas, snakes, and lizards are some of the animals that take refuge in Harrana. A variety of flowering plants bloom during late winter and early spring months, including mustard plants , oriental poppies , and wild irises. Cistanche tubulosa , or the desert broomrape, is another resident in Harrana blooming towards

525-610: The precipitation, even many miles from the source. In areas on or near volcanoes , flash floods have also occurred after eruptions, when glaciers have been melted by the intense heat. Flash floods are known to occur in the highest mountain ranges of the United States and are also common in the arid plains of the Southwestern United States. Flash flooding can also be caused by extensive rainfall released by hurricanes and other tropical storms , as well as

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550-567: The risk of flash floods is not high enough to justify the expense. In fact, in some areas, desert roads frequently cross a dry river and creek beds without bridges. From the driver's perspective, there may be clear weather, when a river unexpectedly forms ahead of or around the vehicle in a matter of seconds. Finally, the lack of regular rain to clear water channels may cause flash floods in deserts to be headed by large amounts of debris, such as rocks, branches, and logs. Deep slot canyons can be especially dangerous to hikers as they may be flooded by

575-485: The stream patterns in the next flash flood . Wind also causes sediment deposition. When wadi sediments are underwater or moist, wind sediments are deposited over them. Thus, wadi sediments contain both wind and water sediments. Wadi sediments may contain a range of material, from gravel to mud, and the sedimentary structures vary widely. Thus, wadi sediments are the most diverse of all desert environments. Flash floods result from severe energy conditions and can result in

600-442: The sudden thawing effect of ice dams . Human activities can also cause flash floods to occur. When dams fail , a large quantity of water can be released and destroy everything in its path. The United States National Weather Service gives the advice "Turn Around, Don't Drown" for flash floods; that is, it recommends that people get out of the area of a flash flood, rather than trying to cross it. Many people tend to underestimate

625-428: Was used to mean a permanent river, for example: Guadalcanal from wādī al-qanāl ( Arabic : وَادِي الْقَنَال , "river of refreshment stalls"), Guadalajara from wādī al-ḥijārah ( Arabic : وَادِي الْحِجَارَة , "river of stones"), or Guadalquivir , from al-wādī al-kabīr ( Arabic : اَلْوَادِي الْكَبِير , "the great river"). Wadis are located on gently sloping, nearly flat parts of deserts; commonly they begin on

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