Mosul Dam Break Inundation Modelling An example of Scientific Support to DG-ECHO and UN A Annunziato , I. Andredakis, P. Probst Joint Research Centre European Commission 2 nd Scientific Seminar of the Disaster Risk Management Knowledge Centre Rome 9-10 March 2017 - Italian Civil Protection
Table of content • Background • Analysis objectives • Initial and boundary Conditions • Results of the dam break cases • Early Warning Systems • Future activities • Response to our analyses • Conclusions
Mosul Dam, Irak 44 km 11 km 3 of water 2 km dam width 110 m dam height
Historical persepctives • The dam was constructed between 1981 and 1986 • It dams the river Tigris, forming an artificial lake that holds 11.1 km 3 of water • It is located 40km NW of the city of Mosul and its primary function is to supply electricity to the city’s 1.7 million inhabitants and to support irrigation needs. • It is the largest dam in Iraq, measuring 2 km in length and 113 m in height. It is an earth-fill embankment-type dam with a clay core.
The problems of the dam • Since the dam is built on a foundation of gypsum, anhydrite and limestone, water can seep under the dam and compromise its stability, posing the risk of catastrophic failure. • To avoid this, continuous maintenance has taken place since the dam’s opening, in the form of grouting : new leaks are plugged by injecting a cement mixture into the compromised spots. • The grouting stopped in 2014 with the arrival of ISIS. Even if the dam was back in the control of Peshmerga (North Kurdistan) late 2014, the machines for grouting were severely damaged. • In Early March 2016 the Iraq Government announced the signature of a contract with the Italian company Trevi that should restart the grouting operations, which are now ongoing. • Nevertheless the risk of failure of the dam is still present and the international Humanitarian Community decided to send an exploratory mission to Iraq
Analysis objectives (1) • In April 2016, upon request of the OCHA Country Office in Iraq, an UNDAC team and an Environmental Emergencies expert was deployed to support preparedness for a potential failure of the Mosul Dam. • Through networks and partnerships supported by OCHA’s Emergency Services Branch, the following support activities have also been activated: The World Health Organization deployed its Emergency Medical Teams’ • manager to Iraq to develop a protocol jointly with the UNDAC team The European Union’s Joint Research Centre has, through the Union’s Civil • Protection Mechanism, developed a number of dam failure scenarios (including flood maps) UNOSAT has provided satellite imagery • The Joint UNEP/OCHA Environment Unit has provided an overview of • hazardous industrial installations in the flood zones
• The main objective was to understand The determination of the inundation extent and timeline in the first 12 days • The role of the initial lake height on the inundation extent and dynamics • The influence of the controlled discharge into the Tharthar Lake • • Initial assumptions revised on the basis of requests coming from the mission on the field To estimate new conditions (i.e. level reduction to a specific height) • To reply to objection by local institutions (i.e. influence of Tharthar Lake) •
Initial and Boundary Conditions (1) • Tigris River topography • 90 m resolution SRTM data by the CGIAR Consortium for Spatial Information, resampled to 180 m – http://srtm.csi.cgiar.org • Lake modelling • Use of the results of the 2011 survey campaign published in open literature and digitized • Dam Break • Coarse modelling of the break, constituted by 15 nodes that are considered open in the wall of the dam. 3 types of breaks considered: 7%, 26% , 60%.
Lake bathymetry (Issa, 2015)
Dam 340 Main section of the Mosul lake 330 Elevation a.s.l. (m) 320 310 300 290 280 270 260 250 0 10 20 30 40 50 60 67 240 Lake of Mosul dam Tigris river Mosul lake main section Mosul lake shore Mosul dam Mosul dam and plant area Elevation a.s.l. (m) 321 254
Simulation of the break The break is opening instantaneously, creating a critical flow at the edge of the water. The instantaneous opening can be considered a conservative assumption or a sudden explosive break
Initial and Boundary Conditions (2)
Initial and Boundary Conditions (2)
Initial and Boundary Conditions (2)
Lake Height: 330 m, break size 26%
Mosul Baghdad
330 m lake height Mosul: max. 26m
Sensitivity Analysis on Lake height Simulated lake Arrival time vs. Lake Elevation heights: 150.00 Time of arrival (h) 330m, 100.00 319m (current), 50.00 315m (proposed), 0.00 309, 307, 295 300 305 310 315 320 325 330 335 Lake Elevation (m a.s.l) 305, 300m Mosul Banyji Tikrit Samarra Bagdad Linear (Mosul) Linear (Banyji) Linear (Tikrit) Linear (Samarra) Poly. (Bagdad)
Sensitivity Analysis on Lake height Simulated lake Maximum height vs Lake Elevation heights: 30 330m, Maximum height (m) 20 319m (current), 10 315m (proposed), 0 295 300 305 310 315 320 325 330 335 309, 307, Lake Elevation (m a.s.l) 305, 300m Mosul Banyji Tikrit Samarra Bagdad Linear (Mosul) Poly. (Banyji) Linear (Samarra) Linear (Bagdad)
Population affected Current Lake Level (319m) Population Impact: 4.5 million people 1.5 million in water > 2m 140 000 in water > 10m
The effect of the discharge into the Tarhar Lake • After the performance of the previous calculations, the preliminary assessment by the UN team onsite with the local authorities pointed out that in the calculations the presence of the connecting channel between Samarra and the Tharthar Lake was not considered. • The presence of this channel could, in principle , relieve the amount of water coming from the Mosul dam reservoir in the direction of Baghdad, diverting it towards the lake and thus reducing the inundation of the Baghdad plane. • According to local engineers the maximum flow in this channel is in the order of 30000 m 3 /s, which however seems not realistic (i.e. Rio de la Plata 22000 m 3 /s).
It is not clear how the control of the water flowing to Tharthar lake is performed. Apparently no control structure appears on the channel to Tharthar lake, so the only control is performed with the dam towards Bagdhad
Channel modelling
Lake height: 315 m with diverting channel
• Minor influence of the diverting channel • The inundation of Baghdad is not prevented by the channel • The volumetric flow to the channel is less than 3000 m 3 /s while the incoming flow is one order of magnitude larger
Critical infrastructures
Colour-coded Affected Chemical Sites
Early Warning Systems • Objectives: • Identify critical conditions for the dam • Raise awareness on possible need for evacuation • Alert that evacuation is necessary: avoid false alerts ! • Last Mile Communication: the information needs to reach the people ! • JRC experience on Tsunami Alerting Systems & Last Mile • Monitoring Sea Levels • Information & alerting panel
Alerting logic based on sequence of measured level alerts Control The alerting could be given Box with 1-1.5 h lead time , which is rather large time if a proper preparedness of local people is performed Water Level Time
Nice review of the study by Prof. Al Ansari • … As a conclusion this study may be considered as comparable to the SC in its comprehensiveness and end results. This study, however, surpasses all the previous studies even the SC study by estimating the possible number of affected population and giving indications of the amount of material destruction at each level of inundation. • (SC=Swiss Consultant) • … • 1. The JRC dam break study being the most up to date and most comprehensive study done so far , so it must be checked for any areas of improvements weather in the assumptions or the updating of population statistics. The outputs of this study shall also define “Rescue Line” in all the threatened zones for each reservoir water level scenario. Contour maps indicating these rescue lines should be prepared and projected on the ground with participation from the government to mark these rescue lines http://ltu.diva-portal.org/smash/get/diva2:982079/FULLTEXT01.pdf
Several references to our study from press 2016
Conclusions • The flood wave will reach the city of Mosul in less than 2 hours, with heights of more than 20m in around 3 hours and its maximum height at the city, 26m , after 6 hours . • An area housing about 180 000 people, almost 10% of the city’s population, would be exposed to a flood wave of more than 10 m • The water will continue downstream, having still a very significant height that is only slowly reduced and affect a total of about 6 million people. A total of more than 500 000 people (including Mosul) would be exposed to flood waves of more than 5 m. • According to these simulations, in the case of Mosul, an evacuation within 4 to 5 km from the river would be advisable.
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