Jordanian Army known as Black September. The Jordanian Army defeated the PLO in 1971, and the latter were expelled to Lebanon. The first wave of Iraqi and Kuwaiti refugees settled in the city after the 1991 Gulf War, with a second wave occurring in the aftermath of the 2003 invasion of Iraq. On 9 November 2005, Al-Qaeda under Abu Musab al-Zarqawi's leadership launched coordinated explosions in three hotel lobbies in Amman, resulting in 60 deaths and 115 injured. The bombings, which targeted civilians, caused widespread outrage among Jordanians. Jordan's security as a whole was dramatically improved after the attack, and no major terrorist attacks have been reported since then. Most recently a wave of Syrian refugees have arrived in the city during the ongoing Syrian Civil War which began in 2011. Amman was a principal destination for refugees for the security and prosperity it offered. During the 2010s, the city has experienced an economic, cultural and urban boom. The large growth in population has significantly increased the need for new accommodation, and new districts of the city were established at a quick pace. This strained Jordan's scarce water supply and exposed Amman to the dangers of quick expansion without careful municipal planning. Geography Amman is situated on the East Bank Plateau, an upland characterized by three major wadis which run through it. Originally, the city had been built on seven hills. Amman's terrain is typified by its mountains. The most important areas in the city are named after the hills or mountains they lie on. The area's elevation ranges from . Al-Salt and al-Zarqa are located to the northwest and northeast, respectively, Madaba is located to the west, and al-Karak and Ma'an are to Amman's southwest and southeast, respectively. One of the only remaining springs in Amman now supplies the Zarqa River with water. Trees found in Amman include Aleppo pine, Mediterranean cypress and Phoenician juniper. Climate Amman's position on the mountains near the Mediterranean climate zone places it under the semi-arid climate classification (Köppen climate: BSh borders on BSk). Summers are moderately long, mildly hot and breezy; however, one or two heat waves may occur during summer. Spring is brief and warm, where highs reach . Spring usually starts between April and May, and lasts about a month. Winter usually starts around the end of November and continues from early to mid-March. Temperatures are usually near or below ,