Derna / Darnah
On September 11th, Storm Daniel tore through eastern Libya. In the days prior to making landfall in Libya, the same low-pressure storm (named Storm Daniel by the Hellenic National Meteorological Service) swamped parts of Greece, Turkey, and Bulgaria. As the storm approached Libya, it developed characteristics of a tropical-like cyclone, or “medicane,” with winds measuring around 70 to 80 kilometers (43 to 50 miles) per hour.
Derna, a city of roughly 100,000 people, was devastated by heavy flooding caused by Storm Daniel. Severe flooding hit parts of Greece after Storm Daniel brought extraordinary amounts of rain to the region. Heavy rainfall brought by Storm Daniel quickly led to massive flooding across several areas in eastern Libya, which is controlled by a different government. The storm hit the cities of Benghazi, Susa, Bayda and al-Marj, among others, on 10 September 2023, but the port city of Derna bore the brunt. The city is surrounded by mountains, so the flash floods quickly took over, with water levels rising as high as 3 meters (10 feet).
What makes Storm Daniel particularly unusual is its subtropical nature, occurring in the Mediterranean during July and September. The Mediterranean region is not typically associated with such weather phenomena. Storm Daniel, which had previously battered Greece and Turkey, had been downgraded to a subtropical storm by September 9. Despite this downgrade, it posed a significant threat to Libya, with forecasts predicting "severe effects" for the nation, according to the Middle East meteorological service Arab Weather.
The Arab Regional Weather Centre issued a report on the storm's progress, noting its arrival on the north-eastern coasts of Libya in Benghazi. The report highlighted the potential impact on areas such as Benghazi, Al-Marj, Al-Bayda, Shahat, Tobruk and Derna. High-speed winds, ranging from 120 km/hour to 180 km/hour, coupled with substantial rainfall of "50-250 mm", were expected.
Entire neighborhoods, especially ones located along the Wadi Derna that runs down from the mountains through the city, were destroyed. A wadi is an Arabic term referring to a valley that may contain water during times of heavy rain. The Sahara Desert covers most of North Africa. Rainfall is scarce, and it comes and goes rapidly, flowing through channels called wadis. When dry, the wadis are revealed as pale tracings across the darker brown and gray shades of the desert landscape. In many cases, these wadis end in small pools which have no outlet.
Flash flooding is becoming more common as a result of extreme weather conditions. The variation in high-velocity of the rainfall over a short duration is responsible for flash flooding values the heavy sediment load that threatens the lower part of settlements in the wadis. A flash flood is usually caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours. Flash floods are usually characterized by raging torrents after heavy rains that rip through river beds, urban streets, or mountain canyons sweeping everything before them. They can occur within minutes or a few hours of excessive rainfall. They can also occur even if no rain has fallen, for instance after a levee or dam has failed. Flash floods are common in desert landscapes after heavy rainfalls and in areas with shallow soil depths above solid bedrock that limits the soil’s ability to absorb rain.
By 12 September 2023 at least 3,000 people were dead in Derna alone, and bodies were still being pulled out of the water in large numbers, with fatalities likely exceeding 6,000. Some of the bodies may have been washed out to sea along with the homes that were swept away by the flash floods. The International Federation of Red Cross and Red Crescent Societies said the number of people missing was nearing 10,000.
There was widespread destruction across Libya’s east after Storm Daniel led to heavy flooding. But the collapse of two dams in Derna, which gave out under pressure they could not handle, was the worst of it. The dams caving under the pressure of water gathering behind them during the storm led to thousands of deaths in the port city alone. There were two major dams upstream from Derna that had not been maintained since 2002. The dams were not very large, with the first dam, the Al-Bilad Dam, only 75 meters (250 feet) tall, and the lower dam, the Abu Mansour Dam, which is about 1 km south of the heart of the city and 13 km south of the first dam, was much smaller.
A research paper published in November 2022 by Omar al-Mukhtar University hydrologist Abdelwanees A. R Ashoor warned that the dams holding back the seasonal waterway needed urgent attention, citing a number of floods that had repeatedly struck the river basin since WWII. "The annual runoff volume for forty years during 1960–2000 in the study area was estimated by 138.51 Mm3. Furthermore, a volume flood has been estimated, based on the flood of October 1945 and late November 1986. Those events called for average precipitation of 145 and 64.14mm respectively. The rainfall of 1945 produced a volume flood of 53.36 Mm3, which represents 40 % of annual runoff volume, while the flood of November 1986 was 14.8 Mm3, which is in good agreement with the recorded flood in the basin. The results demonstrated that the study area has a high potential for flood risk. Therefore, dams of Wadi Derna basin is needed periodic maintenance. Moreover, increasing vegetation cover is required to reduce the phenomenon of desertification."
The 1941 flood, which caused great losses to the German army, the 1956 flood, the catastrophic flood of 1959, the 1968 flood, and the 1986 flood, which, although large, the dams played their role in preventing damage to the city. The 1959 flood remains the most painful in the city’s memory due to the number of victims and material losses.
As a result of the frequent occurrence of floods in the city due to the valley passing through its center, studies conducted in the 1960s recommended the necessity of constructing more than one dam in order to protect the city and to reserve the huge amounts of water that flows through the valley at the time of flood and ends up in the sea. The presence of dams during the past fifty years created a state of reassurance among people, which made them construct fields, orchards, buildings, roads, and facilities on the banks of the wadi that were not intended throughout history to be the site of such constructions.
The two Wadi Derna dams were built between 1973 and 1977 by Yugoslav construction company Hidrotehnika-Hidroenergetika, now based in Serbia, as part of an infrastructure network that would irrigate surrounding fields while supplying Derna and nearby communities with much-needed water. The two dams, dubbed Derna and Mansour, were clay-filled embankment dams (the core is made of compacted clay, and the sides are made of stones and rocks) with a height of 75 meters and 45 meters respectively. The Derna dam’s storage capacity was listed as 18-22.5 million cubic meters of water, while the smaller Mansour dam had a capacity of just 1.5 million cubic meters.
The September 2023 flood was the most severe, destructive, destructive and painful in the history of this city for several reasons. The amounts of rain that fell in a period of less than 24 hours exceeded 200 mm in the valley’s catchment basin. This means that the catchment basin received more than 115 million cubic meters of water, an amount vastly greater than the combined bearing capacity of the dams. These quantities had not been recorded previously in all recorded floods (what is meant is rain falling over several hours).
Unlike previous floods, where water was flowing freely through the stream, the flood was due to the large quantities that had accumulated behind the dams, in addition to the huge additional amounts of water brought to the valley, which made this flood historic and unprecedented. One of the evidence for this is that the shrines of the Companions of the Messenger of God remained there since the Islamic conquest, despite all the floods throughout history, until the dawn flood that swept away them and several meters below them, and the location of those shrines is now in the air several meters above the surface of the ground.
There is no doubt that this flood had never been seen before in the city throughout its history. Everything has changed, including the city’s landscape. The valley has now expanded to include several streets and neighborhoods on its sides and along its course in the city. Today, the city is without protection from any other flood, even if it is minor.
The dams that failed were not the soaring concrete structures backed by vast reservoirs filled by great rivers. Although details are lacking, they were embankment dams constructed of soil and rock, "damming" no more than a dry wadi or scattered pools of water. They were built to control the floods that could race down the dry wadi during periods os scarce rainfall. Surely they were designed to respond to climatic conditions prevailing in the mid-20th Century, not those of early 21st Century.
Seepage plays a significant role in the performance of an embankment dam. Internal erosion is one of the leading causes of dam failures. Too often, the justification for not addressing a possible seepage concern with an embankment dam is that it has performed well for decades and there is nothing to indicate that it would not be expected to continue to perform in a similar manner, and therefore no action is required. Many geotechnical problems are difficult to identify with regards to critical seepage mechanisms within an embankment dam,
Once one dam collapsed, the second one faced a losing battle. Not only did it have to deal with heavy rain that was still pouring down in the storm, but it was also hit with a raging wall of water released with force from behind the other much larger dam. The multiplied force of the water was only strengthened due to the elevation difference between the first and second dams, and the stream took the second dam down on its way to Derna and ultimately, the sea. Coming down the river, the water travelled approximately 12km (seven miles) from the top of the first dam before it reached the sea. Experts estimate that 30 million cubic meters of water were released when the dams broke, equivalent to 12,000 Olympic-sized swimming pools.
Both dams were equipped with Morning-glory or glory-hole spillway towers, located on an abutment over a hundred feet high above the wadi. Instead of a typical spillway, water drains by going down a big hole. The tunnel and outlet channel would be lined with concrete. The glory-hole works like a giant drain, as swirling water drops through a vertical shaft and then discharges downstream through a tunnel. When the reservoir behind the dam fills, water begins to flow over the emergency spillway known as the "Morning Glory" hole. Glory hole spillways are designed for throat control at maximum water surface, unless earlier throat control is needed for limiting downstream releases.
A drop drain (glory hole) spillway has a limited capacity, so an additional spillway have been needed in the event of rainfall rates greater than those for which it was designed, but none was present. If the water surpassed the spillway level (glory hole), it would then be an uncontrolled release over the top of the dam.
Embankment dams are constructed of earth or rock fill that relies on its weight and various material characteristics to control seepage for its stability. Embankments for the storage of water for irrigation, as attested to both by historians and archaeologists, have been used since the early days of civilization. The material comprising the dam must be sufficiently impervious to provide an adequate water barrier. Soils meeting this requirement generally have shear strengths such that the slopes of the dam must be relatively flat for stability.
Failure of dams and levees due to overtopping is a common failure mode. Embankments overtopped by a few inches to a foot or more have performed well but others have failed quickly. Many older dams and levees may have been designed for floods that no longer represent a remote flood event and design flood estimates have increased. Continuous overtopping occurs when water depth exceeds crest of an embankment resulting in continuous flow over the structure. Most embankment dams and levees would likely not withstand sustained overtopping of a foot to two feet or more without a high probability of failure. The embankment crest is lowered and (eventually) breach occurs.
Located along Libya's eastern littoral in an area bracketed with rocky hills, Derna's beautiful, if bleak, setting and Soviet-style poured concrete buildings evoke Tyre and Sidon in South Lebanon. the Baab al-Shiha neighborhood, site of the town's old fort (now all but gone) was a lower-middle class neighborhood, comprising poured concrete homes crowded along largely unpaved streets, sitting on a hill overlooking the town.
It was "well-known" that a large number of suicide bombers (invariably described as "martyrs") and foreign fighters in Iraq hailed from Derna, a fact in which the town "takes great pride". Residents of eastern Libya in general, and Derna in particular, viewed the al-Qadhafa clan as uneducated, uncouth interlopers from an inconsequential part of the country who have "stolen" the right to rule in Libya.
A "large number" of Derna's citizens were not happy about the increasingly conservative religious atmosphere that had prevailed since the 1980s. A dearth of social outlets for young people in Derna "created space" for the message of returned fighters and conservative imams, who deliberately sought to eliminate the few social activities on offer for young people to monopolize the social and cultural environment. While Derna's social life had never been robust, there had been public cinemas, sports leagues and some youth activities organized outside the auspices of mosques. Virtually all of those had petered out in the late 1980's and 1990's, in part because of a campaign to label such activities as "un-Islamic".
The inspiration of the line of the US Marines hymn "to the shores of Tripoli" came during the Battle of Derna. With the unsatisfactory result of the bombardments of Tripoli in 1804 the Tripolitan War had languished in a stalemate. The Americans were able to assemble a mixed force of some 400 men, composed of 38 Greek mercenaries, 25 mostly European artillerists, 90 men serving under Hamet Karamanli directly, 190 camels and their drivers, a small force of Arab cavalry, and eight US Marines commanded by First Lieutenant Presley Neville O'Bannon. This force began its march in Egypt on 8 March 1805, and after six weeks of mutiny, hunger, thirst, Arab intransigence and religious tension arrived on 25 April before Derna, the eastern-most fortified town under Tripolitan control.
William Eaton, despite the fact that the garrison consisted of 945 cavalry and 1,250 infantry, called on Governor Mustapha Bey to surrender, a summons that was contemptuously rejected. Supported by gunfire from the brig Argus, sloop Hornet and schooner Nautilus, Eaton began an assault on the town on 27 April 1805. Despite the heavy odds, a redoubled effort led by First Lieutenant O'Bannon and Midshipman Mann succeeded in taking the town.
Derna is situated at the north of a large ravine, and is built on a low point of land running out from the foot of a range of barren mountains distant about a mile from the coast. It is on the site of the ancient Darnis, but there are no buildings remaining deserving of notice. The houses were better than those of Bengazi [acording to a traveller's report in 1890].
On September 28, 1911, the Italian ultimatum demanding that Turkey should permit the military occupation of Tripoli was presented to the Porte, and on the 29th the Italian Government declared war. In Cyrenaica the Turks attacked Benghazi on the night of December 10th and 11th and Derna on December 16th and 26th. On the latter occasion the Italians lost 4 killed and 77 wounded. In January Enver Bey, who had now assumed command of the Turks in this quarter, took up a central position near Benghazi, and tried to entice the Italians beyond the range of the ships' guns. Additional reinforcements (including one brigade 4th Division and a combined Brigade) reached Cyrenaica in November and December 1911. On February 11th and again on March 3d vigorous attacks were made on the Italian lines at Derna; on the latter occasion Enver Bey is said to have been wounded. The dirigibles "P2" and " P3," which had now returned from Italy, flew over from Tripoli during these operations, and subsequently carried out reconnaissances, and dropped bombs into hostile camps and entrenchments.
The last serious fighting took place in Cyrenaica. On September 15th the Italian garrison of Derna had advanced their line to Kasr el Lebn and Casa Aronne three miles south-east of the town. On the 17th these positions, which were held by three brigades, were attacked by Enver Bey with a strong force supported by guns. After severe fighting the Turco-Arabs were repulsed with a loss of 1100 killed. The Italian troops present in Libya numbered about 110,000, viz. Tripoli and neighbourhood 45,000; Zuara and Sidi Said 15,000; Homs 6000; Misrata 10,000; Benghazi 12,000; Derna 20,000; Tobruk 6000. The Turco-Arab forces were estimated at about 40,000, with a few guns.
By 2008, frustration at the inability of eastern Libyans to effectively challenge Qadhafi's regime, together with a concerted ideological campaign by returned Libyan fighters from earlier conflicts, played important roles in Derna's development as a wellspring of Libyan foreign fighters in Iraq. Other factors include a dearth of social outlets for young people, local pride in Derna's history as a locus of fierce opposition to occupation, economic disenfranchisement among the town's young men. One Libyan interlocutor likened young men in Derna to Bruce Willis' character in the action picture "Die Hard", who stubbornly refused to die quietly. For them, resistance against coalition forces in Iraq is an important act of 'jihad' and a last act of defiance against the Qadhafi regime.
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