Impact of flood by a possible failure of the Mosul dam.
Date: 2016-05-19
Institutions: Institute for the Protection and Security of the Citizen
Subjects: engineering structure, environmental risk prevention, evaluation method, flood, information technology, natural disaster, natural hazard, resistance of materials, simulation

Impact of flood by a possible failure of 
the Mosul dam 

Hydrodynamic Simulations 

Alessandro  Annunziato,  Ioannis  Andredakis, 
Pamela Probst 

Report EUR 27923 EN 

European Commission 
Joint Research Centre 
Institute the Protection and Security of the Citizen 

Contact information 
Alessandro Annunziato 
Address: European Commission, Joint Research Centre, Via Enrico Fermi 2749, TP 680, 21027 Ispra VA, Italy 
E-mail: alessandro.annunziato@jrc.ec.europa.eu 
Tel.: +39 0332 78 9519 

JRC Science Hub 
https://ec.europa.eu/jrc 

This publication is a Technical report by the Joint Research Centre, the European Commission’s science and 
knowledge service. It aims to provide evidence-based scientific support to the European policy-making process. 
The scientific output expressed does not imply a policy position of the European Commission. Neither the 
European Commission nor any person acting on behalf of the Commission is responsible for the use which might 
be made of this publication. 

JRC Science Hub 
https://ec.europa.eu/jrc 

JRC101555 

EUR 27923 EN 

ISSN 1831-9424 

ISBN 978-92-79-58395-7

doi:10.2788/689469  

© European Union, 2016 

Reproduction is authorised provided the source is acknowledged. 

All images © European Union 2016 

How to cite: A. Annunziato, I. Andredakis, P. Probst; Impact of flood by a possible failure of the Mosul dam; 
EUR 27923 EN; doi:10.2788/689469 

 
Impact of flood by a possible failure of 
the Mosul Dam 

Table of contents

Executive Summary ............................................................................................... 4 

1. Introduction ................................................................................................... 5

1.1  Basic dam information ................................................................................ 5 

1.2  Dam instability .......................................................................................... 5 

2  Hydraulic calculations varying the break size ....................................................... 7 

2.1  Affected population .................................................................................. 14 

3  Sensitivity Analysis on the initial Lake Level ...................................................... 16 

4  Conclusions .................................................................................................. 38 

5 

Limitations and Uncertainties in this study ........................................................ 39 

References ......................................................................................................... 40 

Acknowledgements .............................................................................................. 40 

List of figures ...................................................................................................... 41 

Appendix I: Different scenarios of dam failure......................................................... 42 

Appendix II: Inundation maps of major cities ......................................................... 47 

Appendix III – Maps related to Lake Level Sensitivity Analysis .................................... 4 

2 

3 

 
 
 
 
 
Executive Summary 

The  dam  of  Mosul  on  the  Tigris  river  in  northern  Iraq  is  the  largest  in  the  country  and 
holds around 11 km3 of water. Built on water permeable rock, the inherent instability of 
the Mosul dam has been known since it was built and this was mitigated by continuous 
grouting. In recent years adequate maintenance has not taken place, leading to concerns 
about  the  safety  of  the  dam.  In  2003  the  government  decided  to  lower  the  maximum 
water level from 330 to 319 metres.  During the recent conflict, maintenance has again 
been disrupted and signs at the dam have triggered renewed concerns, highlighted in the 
Schnabel  report.  As  a  result,  the  government  of  Iraq  have  contracted  the  Italian 
engineering company Trevi to undertake remedial work on the dam. This work is scheduled 
to start later in the Spring of 2016. 

In  late  February  2016  the  Iraqi  government  advised  the  residents  of  Mosul  to  move  at 
least 5 km away from the river in case of breach. A UN mission of UNDAC experts left for 
Iraq  in  early  April  to  assess  the  situation,  supported  by  an  associated  expert  from  the 
European Union Civil Protection Mechanism.  

A number of studies have been devoted to the possible effects of a failure of the dam. In 
this  study  we  perform  a  number  of  medium-resolution  (180m)  dynamic  hydraulic 
simulations  starting  from  various  constant  percentages  of  destruction  of  the  dam  and 
allowing the corresponding quantity of water (supposing the lake to be at its highest level) 
to flow downslope for periods of 6 and 12 days. Compared to previous studies we provide 
in addition a complete timescale of the water flow progression, detailed maps of the water 
depth and extent in the affected cities’ areas and focus more on the numbers of population 
affected by various water depths. 

The main scenario analysed in this study, where the dam is 26% destroyed, the level of 
the lake is at its maximum value of 330m, and most of the lake’s water is allowed to flow 
out fast, results in a very high wave of water (in places 25m high, mean height around 
12m) arriving at Mosul city after 1h40min. The capital Baghdad is reached after about 
3.5 days with a max water height of 8m and a mean of around 2m. 

The simulations suggest that in the above scenario a total of more than 6 million people 
(close to one sixth of the country’s population) will be affected by floodwaters, with two 
million of them facing water of more than 2m. Water heights of more than 10m would 
inundate an area with 270 000 people, most of them in Mosul city and its surroundings, 
whose lives, houses and infrastructure would risk complete destruction. 

A number  of  other scenarios involving lower  initial levels of the lake are also analysed, 
considering  levels  of  319m  (the  current  one),  and  315,  309,  307,  305  and  300m. 
Significant reductions in the affected populations and later arrival times are seen for lower 
initial  lake  levels.  The  differences  are  quite  prominent  in  Mosul  as  well  as  in  Baghdad, 
where we also provide detailed maps of the inundation in the various cases. The scenario 
of  part  of  the  flood  wave  being  diverted  to  lake  Tharthar  by  an  existing  channel  near 
Samarra is also examined in detail. 

These results are a first-order approximation, favouring speed of calculation over detail 
for a rapid assessment; it is planned to refine them later using higher resolution ground 
elevation  data  (that  take  much  longer  to  run)  and  more  detailed,  time-dependent 
scenarios of dam failure. 

4 

 
 
 
 
 
1. Introduction 

1.1  Basic dam information 

The dam of Mosul was constructed between 1981 and 1986 in northern Iraq. It dams the 
river Tigris, forming an artificial lake that holds 11.1 km3 of water at full capacity and its 
primary function is to control water flow in the Tigris river. 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. It is the largest dam in Iraq, measuring 2km in length and 113m in height. It 
is an earth-fill embankment-type dam with a clay core.  

Figure 1: The dam of Mosul (Google Earth, 2010) 

1.2  Dam instability 

Concerns about the dam’s stability and safety began already during construction: because 
the dam is built on a foundation of gypsum, anhydrite and limestone, i.e. water-soluble 
minerals, water can seep under the dam and compromise its stability, posing the risk of 
catastrophic failure (Al-Ansari et al 2015 and references therein – Ref. 1). 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.  This 
ad-hoc solution in itself is not deemed satisfactory, since grouting at one location causes 
the seepage of subsurface water to move to another location but does not stop it (Ref. 2).  

In any case, most of this maintenance was stopped in 2014, after the area was taken over 
by the forces of the so-called Daesh. Later in 2014 the area passed again under the control 
of the Peshmerga, the military forces of the autonomous region of Iraqi Kurdistan, but the 
maintenance  has  not  been  fully  restarted  and  fears  about  the  dam’s  stability  have 
multiplied. According to media reports, the grouting machines have been damaged and 
there is no cement supply, and even the gates of the overflow spillway (visible on the right 
of the dam in the photo above) are malfunctioning (Ref. 3). Moreover, as spring advances, 
the water level is expected to increase from snowmelt, increasing further the pressure on 
the dam. Another possible threat that has been mentioned is deliberate destruction of part 
of the dam as a warfare act; this scenario was invoked primarily during the 2003 Gulf war. 

In early March 2016 it was announced (Ref. 4) that the Iraqi government had awarded a 
contract to a European company to resume maintenance and guarding of the dam. It is 
not  clear,  however,  when  the  works  would  actually  start.  The  Iraqi  government  also 
announced an experts’ mission to assess the dam’s stability in late February. (Ref. 5) 

5 

 
 
 
 
 
 
Despite  many  warnings  and  studies  indicating  the  possible  instability  of  the  dam,  the 
official stance of local officials until recently has been reassuring, claiming that the risks 
were exaggerated (Ref. 3). In late February, however, this was reversed, with the Iraqi 
Prime Minister advising the population of Mosul to move at least 5km away from the Tigris’ 
river bed in the case of failure (Ref. 6). 

1.4 Past studies of flood effects by dam failure 

The most detailed study until of the possible mechanisms and eventual effects by failure 
of the Mosul Dam until this day remains the one of Swiss Consultants in 1984, summarised 
in  Ref.  1.  In  that  study  a  number  of  dam  failure  models  were  developed,  based  on  a 
progressive breach of various widths and most of the water of the reservoir was emptied 
in 6 to 8 hours after the initial breach. Most interesting to compare with this present paper 
is  the  tracing  of  the  wave  downstream.  Those  results  of  1984  can  be  summarised  as 
follows: 

- The initial height of the wave is 55m, decreasing to 45m after the first 20km. 

- Mosul city will be affected by the flood 4 hours after the breach; the maximum wave 
height will be 24m and it will inundate 74 km2 of the Mosul city area. 

-  The  city  of  Tikrit  will  be  reached  after  22h  and  the  maximum  height  will  be  15m, 
inundating 69 km2. 

- Northern Baghdad will be reached after 38 hours and central Baghdad after 44 hours, 
with a wave of 4m. A total of 217 km2 will be inundated. 

No  detailed  affected  population  numbers  have  been  calculated  in  this  study;  rough 
estimates in the media mention around 500 000 people in direct risk of loss of life. 

A preliminary study (Ref. 9) on the Mosul dam failure inundation on a much shorter time 
scale  was  carried  out  in  early  March  2016  by  the  Institute  of  Environment  and 
Sustainability of the Joint Research Centre.  In  this 2-dimensional hydraulic modeling at 
low resolution, it was calculated that 4.7 million people would be affected, an area of 7,700 
square km would be inundated and Mosul would face a mean flood depth of 9.8m affecting 
200 000 people. 

Another study by Thair et al (Ref. 10) consider a time for the creation of the break. The 
break  time  is  up  to  about  4h in  the  case  of  330  m  a.s.l.;  in  this  study  we  assumed  an 
instantaneous opening, in order to assess a worst-case scenario. 

6 

 
 
 
 
 
2  Hydraulic calculations varying the break size  

A  number  of  calculations  has  been  performed  in  order  to  estimate  the  dam  break 
propagation from the Mosul dam into the downstream valley in the 6 days following the 
break  event.  The  calculations  have  been  performed  using  the  HyFlux2  computer  code, 
developed at the JRC (Ref. 7) and routinely used for Tsunami and Storm surge events but 
originally developed to analyse dam break problems. 

In  order  to  execute  the  calculations  some 
preliminary  analysis  of  the  topography  and 
retrieval  of  dam  characteristics  have  been 
performed: using those data we proceeded to 
determine  the  original  topography  of  the 
valley  where  the  dam  was  built  (i.e.  without 
the  lake’s  water)  and  definition  of  the  break 
characteristics.  

The original topography has been obtained by the publication of Elias Issa (Ref. 8) that is 
reporting the results of a bathymetric survey in the lake performed in 2011. Unfortunately, 
it was not possible to contact the author and therefore we have used the image below in 
order  to  obtain  the  elevation  above  the  sea  level  of  the  lake  bottom,  i.e.  the  original 
topography  without  the  lake.  the  current  better  available  topography,  i.e.  SRTM  90  m, 
consider the lake at an elevation of 307-310 m. We considered the elevation of the lake 
at  330m  that  is  the  maximum  normal  operational  water  elevation  (and  thus  taking  the 
worst-case scenario as far as water volume is concerned). 

Figure 2: Lake bathymetry (from Issa 2015) 

From the figure above the dam bottom topography has been obtained, resampled at 90m 
and substituted to the STRM90 in the area of the lake.  The dam break has been simulated 
by considering a reduction of pixels in the topography so that water could flow out of the 
lake. 

The following figure represents the topography of the dam valley with the dam simulated. 
To simulate the break, a few pixels of those that play the role of the dam (red squares in 
the  figure)  have  been  substituted  by  lower  pixels  in  order  to  allow  a  direct  connection 

7 

 
 
 
 
between the lake and the descending section located at 252 m with a jump of 78 m from 
the lake top, assumed at 330 m. 

Considering that the dam to be 2 km long and 78m high (measured from the level of the 
river), for a total of 156000 m2 the assumed break area is about 26% of the total area and 
is as high as the total height of the dam. 

Lake Bathymetry as obtained for this study 

8 

 
 
 
 
 
 
 
 
 
Break simulation 

Figure 4: Dam breach representation 

Figure 3: Dam breach profile 

330 m 

252 m 

9 

 
 
 
 
 
 
 
 
The above break can be considered a large one, as the total elimination of the whole dam 
from top to bottom might not be realistic. For a sensitivity analysis, a case with 60% area 
break was run; the results of this 60% break are not very different from the ones of 26%, 
used in the rest of the study. A case with a strong reduction of this area was also run, with 
an area of only 7% limited to the upper part of the dam, to simulate a deliberate explosion. 
The  results  of  the  26%  case  here  are  therefore  considered  representative  of  a  rather 
severe break. Indicative results and maps resulting from the other scenarios are given in 
Appendix I. 

Results of the dam break event (26% break) 

The propagation of the water flow is indicated in the time sequence below for the 6 days 
of  the  simulation.  The  simulation  was  run  using  10  cores  on  a  Linux  machine  with  a 
resolution of 180 m per each cell and took about 24 h of CPU time. 

10 

 
 
 
 
 
 
 
Figure 5: Time evolution maps of the water flow. 

11 

 
 
 
 
 
Figure 6: Overview map of water flow and travel time (Initial lake level: 330 m) 

12 

 
 
 
 
 
 
The progression of the flow in the valley occurs following the average local slope. At the 
beginning, when the slope is higher the speed is quite large, in the order of 40 km/h. The 
speed then decreases and finally almost stops in Baghdad where a very flat area exists. 
As can be seen also from the plot below, at the various cities upstream of Baghdad the 
water is kept high but for much shorter periods, while in this last city the height of the 
water  is  lower  but  stays  for  much  longer.  The  flow  progression  can  be  visualised  as  an 
animation in this URL: http://goo.gl/6CT5ig   

Item 

Height 
(metres 
a.s.l) 

Distance 
(km)1 

Slope 
(%) 

Average 
speed 
(km/h) 

Time 
wave 
arrival 
(h)2 

of 

of 

Time 
max 
height (h) 

Max 
Height 
(m) 

Dam break 

252 

0 

- 

Mosul 

217 

69  

-0.05 

Bayji 

Tikrit 

Samarra 

Bagdad 

109 

180   

-0.06 

89 

66 

38 

47 

-0.04 

54 

-0.04 

108 

-0.03 

0 

1.7 

0 

78 

6.2 

26.4 

16.8 

23.5 

14.3 

21.0 

26.5 

14.4 

25.8 

30.8 

16.1 

67.0 

117.0 

7.9 

40. 

11. 

11. 

18. 

2.6 

Figure 7: Water height versus time for the lake and for the major cities downstream. 

1 Distance between two points 
2 Time of arrival is considered at the city centre. In the case of Baghdad the periphery is 
reached a few hours earlier 

13 

 
 
 
 
 
 
 
 
                                           
2.1  Affected population 

For  population  calculations  in  this  section  we  use  the  same  scenario  as  above,  i.e. 
maximum initial lake level of 330m. To obtain numbers for the population affected by 
the flood wave we superimposed the maximum water height maps of the above analysis 
on the LANDSCAN 2014 Global Population Database, with a resolution of approximately 
1km2. Altough SRTM 90m is the best complete available topography layer (Sentinel data 
are sparse for this region), it is important to mention that the in some areas there could 
be  local  errors  which  could  affect  the  flood  depth  and  flood  extent,  therefore  the  maps 
should  be  used  with  caution  and  always  considering  real  ground  conditions.  In  the 
estimation of the population possibly affected current refugee camps and displaced people 
are not included and may be included, if available, in a future revision of this document. 

The floodwave raster was binned in 5 water height classes, with these limit values: 0.1m, 
0.5m, 2m, 5m, 10m. Any area with more than 0.1m of water we consider to be affected 
by flooding. The total population and area affected by the different water heights is given 
in the table below: 

The  total  population  affected  by  floodwaters  higher  than  0.1m  is  a  little  over  6  million 
people or a very significant  16% of the total population of  Iraq. The flooded area is 
close to 2% of the country’s total surface.  

A sub-total of more than half a million people would be exposed to floodwaters of 
more than 5m high, thus having their lives at immediate peril; a large percentage  of 
those would have less than two hours warning time, as will be shown below. 

Moreover, a very significant surface area will be inundated, with subsequent destruction 
of critical infrastructure, houses, crops and all livelihood. The cost of the damage is not 
easy  to  calculate,  but  it  is  easy  to  understand  that  the  scale  of  the  disaster  would  be 
enormous  and  the  economic  impact  in  the  country  and  the  whole  region  would  be 
impossible to bear. 

We repeated the above calculation for the greater areas (5 – 10 km from the city centre) 
of five major cities along the Tigris river and the results are shown in the Table below. 

14 

 
 
 
 
The lower part of the Table gives the time for the arrival of the first volume of water, that 
of the maximum height (that in general has a significant delay of at least a few hours with 
respect to the first wave) and the maximum water height in meters. (These figures are 
copied  and  rounded  from  the  table  with  the  detailed  results  of  the  simulations  in  the 
previous Section). 

It is worthwhile to comment further on the case of Mosul – the reader is also referred to 
the detailed map of the inundation in each of the above cities, in Appendix I. There are a 
few  points to highlight: 

1.  The city is built on either side of Tigris, with densely inhabited neighbourhoods 
close to the  river. As a result, a very large number  of people will be exposed to 
prodigious heights of floodwater: 183 000 people, more than 10% of the city’s 
population of 1.7 million will be affected by more than 10m wave height, which 
could mean complete destruction. 

2.  The  warning  time  will  be  very  short;  even  if  a  dam  breach  is  signalled 
immediately,  within 3 hours the  water height in Mosul will have already reached 
close to 20m (see the graph with depth and time reached in the previous chapter). 
Evacuation of almost 250 000 people from the banks of Tigris in a few hours is very 
difficult to accomplish. 

3.  Due to the ground morphology, as can also be seen in the map in Appendix I, the 
water  level  drops  sharply  at  around  4  km  away  from  the  river  bed.  A  possible 
evacuation, therefore, would have to be carried out at this distance; the value of 
4-5km agrees well with that recommended by the Iraqi government in March 2016. 
4.  The value for the maximum wave height in Mosul in these calculations is in good 
agreement  with  the  values  estimated  in  the  study  of  Swiss  Consultants  in  1984 
(24m). The time of arrival is also in good agreement: SC gave a value of 4h for a 
wave of 24m, while we give 3 hours for 20m and 6 hours for the maximum of 26m. 

Significant damage and loss of life should also be expected in the other cities along the 
river, with very high water levels of more than 10m present. It is interesting to notice that 
in  Samarra,  a  long  way  downriver,  the  maximum  height  is  actually  larger  than  that  of 
Tikrit, higher upstream. 

In Baghdad, heights of up to 8m were shown by the calculations in a few places; the mean 
value in the Baghdad greater area, however, is quite lower, at around 2m.  More than 1 
million people would be exposed to depths of 2-5m. What is worrying in this case, as can 
be seen in the height-time graph in the previous section, is that the floodwaters take much 
longer to drain away from the Baghdad area, owing to the flat ground morphology. 

15 

 
 
 
 
3  Sensitivity Analysis on the initial Lake Level 

On  request  of  the  UNDAC  team  onsite  a  number  of  additional  calculations  have  been 
performed in order to assess the effect of the lake level reduction on the inundation depth 
and  extent.  The  initial  break  size  was  kept  as  the  intermediate  case  (26%  of  the  total 
area)  as  we  saw  no  large  differences  with  the  60%  break  and  because  we  considered 
unrealistic a complete or partly complete destruction of the dam. 

The following cases have been considered from 300 m (minimum operational level for the 
power plant) to 330 m (the base case maximum): 

Elevation 
(m a.s.l.) 

Initial 
Volume 
(km3) 

Final 
Volume 
(km3) 

330 

319 

309 

307 

305 

300 

9.6 

5.9 

3.6 

3.3 

2.9 

2.2 

0.5 

0.5 

0.5 

0.5 

0.5 

0.5 

Discharged 
Volume 
(km3) 
9.1 

5.4 

3.1 

2.8 

2.4 

1.7 

The  reduction  of  the  initial  water  level  strongly  reduces  the  amount  of  water  that  is 
discharged in case of break from about 9.1 to 1.7 cubic km; the release time is increased 
from 12 to 21 hours3. 

The  effect  on  the  maximum  water  height  and  arrival  time  can  be  seen  in  the  following 
tables and plots.  

The effect of the reduction on the maximum height is more evident in Mosul rather than 
in Baghdad, where the maximum height remains unchanged but the larger effect is on the 
extent  of  the  flooding  as  lowering  the initial  height  the  flooded  area  is  largely  reduced, 
consistently with the reduction in the discharged volume. The highest lake area cases will 
be extended beyond 6 days while all the other cases have been run for 12 days. 

Appendix B reports all the maps related to these cases. The map below shows the variation 
of the inundated areas in Baghdad by increasing the lake height. It is possible to note the 
larger inundation that takes place as the lake height is increased.  On the right of the map 
the arrival times are also shown and it is possible to note how the lake height reduction 
tends to move the arrow related to 1 day to northern area, which means that the time for 
arriving to the various locations increases. 

The tables after the next map indicate the 
population  and  area  affected  by  varying 
the lake level. As a whole, from 6.2 million 
people  globally  affected  the  population 
globally  affected  reduces  to  2.2  million, 
thus  at  least  1/3  of  the  population 
affected by the largest height. The figure 
on 
the  overall 
population  as  a  function  of  the  lake 
height. 

indicates 

right 

the 

Population vs Lake Height

8

6

4

2

0

290

300

320
310
Lake Height (m absl)

330

340

n
o
i
t
a
d
n
u
n

i

l

r
e
d
n
u
e
p
o
e
p
f
o
n
o

i
l
l
i

M

3 Release time is difficult to  establish because the level  is decreasing exponentially. We 
consider arbitrarily as the time at which the level is smaller than 1m 

16 

 
 
 
 
 
 
                                           
 
 
 
 
 
Maximum Height 

Lake Elevation  Mosul 

Banyji 

Tikrit 

Samarra 

Bagdad 

330 

319 

309 

307 

305 

300 

26.3 

22.7 

19.2 

18.6 

17.9 

16.0 

14.3 

11.8 

9.3 

8.9 

8.3 

7.3 

14.5 

11.8 

9.5 

9.1 

8.7 

7.8 

16.1 

13.8 

11.1 

10.4 

9.9 

8.3 

8.0 

7.6 

7.5 

7.4 

7.3 

7.1 

Maximum height vs Lake Elevation

)

m

(

i

t
h
g
e
h
m
u
m
i
x
a
M

30

25

20

15

10

5

0

295

300

305

310

315

320

325

330

335

Lake Elevation (m a.s.l)

Mosul

Samarra

Banyji

Bagdad

Tikrit

Linear (Mosul)

Poly. (Banyji)

Linear (Samarra)

Linear (Bagdad)

17 

 
 
 
 
 
 
 
 
 
 
Arrival times  

Lake Elevation 

Mosul 

Banyji 

330 

319 

309 

307 

305 

300 

1:40 

2:29 

2:55 

2:54 

3:17 

3:40 

16:56 

18:59 

22:54 

23:45 

24:53 

28:32 

Tikrit 

21:08 

24:07 

29:00 

30:04 

31:19 

35:58 

Samarra 

Bagdad 

26.12 

30.05 

36.48 

38.12 

40.12 

46.18 

76:15 

76:20 

96:40 

103:05 

111:31 

141:33 

Arrival time vs. Lake Elevation

)
h
(

l

a
v
i
r
r
a
f
o
e
m
T

i

160.00

140.00

120.00

100.00

80.00

60.00

40.00

20.00

0.00

295

300

305

310

315

320

325

330

335

Lake Elevation (m a.s.l)

Mosul

Bagdad

Banyji

Tikrit

Samarra

Linear (Mosul)

Linear (Banyji)

Linear (Tikrit)

Linear (Samarra)

Poly. (Bagdad)

18 

 
 
 
 
 
  
 
 
 
 
19 

 
 
 
 
20 

 
 
 
 
 
 
 
 
21 

 
 
 
 
 
 
 
 
22 

 
 
 
 
 
23 

 
 
 
 
24 

 
 
 
 
 
 
 
 
 
4  Role of the connecting channel between Samarra and Tharthar 

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, at the location where a dam on the Tigris river 
is located 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 30 000 m3/s, which however seems not realistic. 

For these reasons, and due to the fact that the newly decided lake level was decreased 
from 319 to 315 m, it was decided to perform additional calculations taking into account 
this additional detail. 

4.1  The channel 

The channel in question is visible in the image below obtained by Google Earth. The length 
of the channel is about 77 km and the width ranges between 40 and 130 m, as indicated 
in the image. The height drops from 62 to 44 m, i.e. 18 m for an average slope of 0.23 % 
and a max slope of about 2%. 

Samar
ra 

Tharthar 
Lake 

25 

 
 
 
 
 
 
 
The  image  below  shows  the  point  where  the  channel  starts,  Qulah  Town.  On  the  left  a 
Hydropower dam creates the lake but after the dam a jump of about 10 m is present which 
means that (considering the flood wave height at this location of about 8 m) the dam does 
not offer a great protection for the locations downstream, and most of the water would 
naturally flow on the left, toward Baghdad. On the right lies the entrance to the channel 
in question towards Tharthar lake, which flows for a long distance at the same elevation 
(62-64 m) before losing large part of the 18 m in the last part of its trajectory. 

Baghdad 

Tharthar Lake 

Dam 

The  image  below  shows  superimposed  the  inundation  corresponding  to  319m  of  Lake 
elevation to show that all this area is largely inundated. It is however not clear how much 
water tends to flow towards Baghdad and how much would be spilled away through the 
channel. 

26 

 
 
 
 
 
 
 
The Samarra dam is constructed with a wall of about 10m and it is not clear how much is 
the height of the dam above the normal water level upstream. We assumed it to be in the 
order of 2 m. 

Towards 
Lake 
Tharthar 

Towards 
Baghdad 

27 

 
 
 
 
 
 
 
 
 
4.2  Modelling of the channel 

The original SRTM bathymetry (90m) does not show clearly the presence of the channel 
even if the overall plane is present. In order to maximize the flow from the channel towards 
the  lake,  the  channel  has  been  modelled  considering  the  original  path,  a  continuous 
decreasing  elevation  from  64  to  44  m  and  including  walls  of  maximum  height  64  m  to 
contain the water in the channel.  

Lake Tharthar 

Channel 

Bagdhad Plane 

The width of the channel is 2 pixels (184x2=368 m) which is much more than in reality 
but we wanted to be sure that the water could flow even at this resolution. The presence 

28 

 
 
 
 
 
of the walls (red in the figure above) is important to avoid that  part of the water could 
flow down on the right, as indicated by the yellow arrow in the previous figure.  

In order to prevent an immediate flow towards Baghdad, the dam has been raised by 2 m 
above the initial water level but given the very high flow and velocity some doubts exist 
that  this  dam  could  resist  the  large  moment  of  water  arriving.  Nevertheless,  it  was 
maintained for the whole calculation. 

4.3  Dam  break  calculations  with  the  channel  simulated  and 

with 315 m initial lake elevation  

Mosul Lake 

In  order  to  understand  the  various  overall 
water  movements,  the  calculation  space  has 
been subdivided in 5 zones, as indicated in the 
figure on the right.  

The results of the calculations are reported in 
terms  of  volume 
in  each  section  and 
derivative  of  the  volume,  i.e.  the  volumetric 
flow  change  per  second.  For  volumes  with 
only  one  connection  like  Mosul  lake,  South 
Samarra  and  Tharthar  Lake  this  quantity 
represents  the  flow  inlet  while  for  North  of 
Samarra  and  the  channel  it  represents  the 
inlet/outlet difference.  

It  is  interesting  to  note  that  the  Lake 
discharges a huge initial flow, i.e. 89000 m3/s, 
the  inlet  flow  into  the  South  of  Samarra  has 
an inflow peaking at 35000 m3/s and therefore 
the channel, whole maximum flow is 3.4 m3/s, 
is insufficient to prevent the inundation of the 
district South of Samarra. 

After the first hours however the channel can 
relief  less  and  less  and  at  the  end  of  the 
transient  condition  the  Tharthar  lake  will 
absorb only 0.3 km3 against 3.9 km3 of South 
Samarra. 

Even if the modelling of the channel could be improved with a more detailed medullisation 
of the flow, we don’t think that the flow rate should be much larger than what indicated. 
One should also consider that the size of the channel is in reality much narrower than what 
here assumed.  

Further maps below show the difference in the inundation between the case with or without 
the contribution of the relief channel. It is obvious to consider that any further increase of 
the initial water level would probably increase the amount of water travelling in the channel 
but at the same time the flow to South of Samarra is even larger; again, we do not expect 
a large contribution of this channel to relieving the water volume flowing toward Baghdad. 

29 

 
 
 
 
)
3

m
k
(
e
m
u
o
V

l

Volume in the different areas

5.00

4.50

4.00

3.50

3.00

2.50

2.00

1.50

1.00

0.50

0.00

0

20

40

60

80

100

120

140

160

180

200

Time from break (h)

Mosul Lake

North Samarra

Channel

Lake Tharthan

South Samarra

Volumetric flows

)
s
/
3
m

(
e
t
a
r

w
o
l
F

10000.0

9000.0

8000.0

7000.0

6000.0

5000.0

4000.0

3000.0

2000.0

1000.0

0.0

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

160.0

180.0

200.0

Time After Break (h)

Channel

Lake Tharthan

South Samarra

30 

 
 
 
 
 
 
 
 
 
 
 
 
Volumes in the various areas (km3) 

Time (h) 

Mosul 
Lake 

North 
Samarra 

Channel 

Lake 
Tharthar 

South 
Samarra 

0 
12 
24 
36 
48 
60 
72 
84 
96 
108 
120 
132 
144 
156 
168 
180 
192 
204 
216 
228 

4.85 
0.98 
0.68 
0.61 
0.58 
0.56 
0.54 
0.53 
0.53 
0.52 
0.52 
0.51 
0.51 
0.51 
0.51 
0.51 
0.50 
0.50 
0.50 
0.50 

0.04 
3.98 
4.32 
3.69 
2.06 
1.24 
0.83 
0.62 
0.51 
0.44 
0.39 
0.36 
0.33 
0.31 
0.30 
0.28 
0.27 
0.26 
0.26 
0.25 

0.00 
0.00 
0.00 
0.15 
0.20 
0.24 
0.22 
0.18 
0.15 
0.12 
0.10 
0.09 
0.08 
0.07 
0.06 
0.05 
0.05 
0.05 
0.04 
0.04 

0.00 
0.00 
0.00 
0.00 
0.00 
0.00 
0.06 
0.12 
0.17 
0.20 
0.23 
0.25 
0.26 
0.27 
0.28 
0.29 
0.29 
0.30 
0.30 
0.30 

0.00 
0.00 
0.00 
0.00 
1.55 
2.55 
3.07 
3.35 
3.50 
3.59 
3.66 
3.70 
3.74 
3.77 
3.79 
3.81 
3.82 
3.84 
3.85 
3.86 

Volumetric flow in the areas (inflow-outflow, m3/s) 

Time (h) 

Mosul 
Lake 

North 
Samarra 

Channel 

Lake 
Tharthar 

South 
Samarra 

0.0 
12.0 
24.0 
36.0 
48.0 
60.0 
72.0 
84.0 
96.0 
108.0 
120.0 
132.0 
144.0 
156.0 
168.0 
180.0 
192.0 
204.0 
216.0 
228.0 

-89611.5 
-7036.7 
-1638.0 
-761.5 
-448.3 
-295.0 
-211.4 
-160.7 
-124.2 
-98.6 
-80.9 
-68.3 
-57.8 
-49.4 
-42.5 
37.0 
-32.5 
-28.0 
-24.7 

91239.6 
7868.4 
-14490.8 
-37812.9 
-18940.9 
-9530.3 
-4810.9 
-2636.1 
-1598.2 
-1086.2 
-778.5 
-590.3 
-456.1 
-362.5 
-298.4 
-248.6 
-212.0 
-185.8 
-160.1 

0.0 
0.0 
3397.7 
1314.6 
780.3 
-422.3 
-829.3 
-788.8 
-621.5 
-468.9 
-353.5 
-263.6 
-203.0 
-161.1 
-126.4 
-95.8 
-75.8 
-60.8 
-51.6 

0.0 
0.0 
0.0 
0.0 
2.9 
1283.0 
1411.7 
1153.7 
857.2 
621.3 
451.4 
328.7 
245.3 
191.4 
147.7 
111.2 
86.4 
68.3 
55.7 

0.0 
0.0 
44.6 
35803.5 
23219.7 
11915.4 
6461.3 
3606.5 
2166.5 
1434.7 
1074.0 
812.3 
659.0 
527.0 
420.1 
364.0 
303.3 
258.9 
232.3 

Note the effect of the dam: 
the channel is filling but no 
water  is  still  going  to 
South Samarra 

This  is  the  only  period 
in which the channel is 
active  and  can  absorb 
water. Once the flow is 
channel 
the 
passed 
empties 

31 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
3 

2 

1 

Flow depth at the positions identified below 

1 

2 

3 

32 

 
 
 
 
 
 
 
 
4.4  Overall results of all the cases, including the 315 m   

Maximum Height 

Lake Elevation  Mosul 

Bayji 

Tikrit 

Samarra 

Bagdad 

330 

319 

315 

Channel 315 

309 

307 

305 

300 

26.3 

22.7 

21.1 

= 

19.2 

18.6 

17.9 

16.0 

14.3 

11.8 

10.6 

= 

9.3 

8.9 

8.3 

7.3 

14.5 

11.8 

10.8 

= 

9.5 

9.1 

8.7 

7.8 

16.1 

13.8 

13.2 

= 

11.1 

10.4 

9.9 

8.3 

8.0 

7.6 

7.5 

7.5 

7.5 

7.4 

7.3 

7.1 

33 

 
 
 
 
 
 
 
 
 
 
Arrival times (hours) 

Lake Elevation 

Mosul 

Banyji 

330 

319 

315 

Channel 315 

309 

307 

305 

300 

1:40 

2:29 

2:35 

= 

2:55 

2:54 

3:17 

3:40 

16:56 

18:59 

20.19 

= 

22:54 

23:45 

24:53 

28:32 

Tikrit 

21:08 

24:07 

25:50 

= 

29:00 

30:04 

31:19 

35:58 

Samarra 

Bagdad 

26.12 

30.05 

32.13 

= 

36.48 

38.12 

40.12 

46.18 

76:15 

76:20 

83.30 

83.52 

96:40 

103:05 

111:31 

141:33 

34 

 
 
 
 
 
  
The affected population figures in the scenario where the existence of the channel leading 
to the Tharthar lake is included in the simulations. The last column marked with an asterisk 
(*) is the figures in Baghdad not considering the channel, given here for comparison. It 
can be seen that the difference is quite small. 

In the column with the area affected, the two first classes (0.1-0.5m and 0.5-2m) are left 
empty since the area of lake Tharthar would enter in these classes, rendering them too 
large and quite meaningless. 

35 

 
 
 
 
 
 
 
 
Time=1d 9 h 

The  water  accumulates  at 
Samarra dam 

Time=1 d 12 h 

Water  overpasses  the  dam 
and  starts  to  flow  towards 
Baghdad and towards the lake 

Time=1 d 16 h 

The  amount  of  water  flowing 
towards Baghdad  is definitely 
much  larger  than  the  one 
going towards the lake 

36 

 
 
 
 
 
 
 
 
 
Time=2d 17 h 

When  the  lake  is  reached, 
most of the Baghdad plane is 
already flooded. 

This  animation  is  available  at:    http://goo.gl/RrlhWe  ;  the  map  below  indicates  the 
comparison  with  and  without  the  channel.  There  is  only  a  small  area  (in  red)  that  is 
inundated more if the channel is not included but the large part of Baghdad is inundated 
in both cases. 

37 

 
 
 
 
 
 
 
5  Conclusions 

In this study we present numerical simulations of the flood wave following a breach of the 
Mosul dam, long known to be potentially unstable due to the water-permeable ground in 
which  it  was  built.  A  few  scenarios  were  run,  within  the  time-limits  set  by  this  rapid-
assessment report, considering the worst case scenario of a full reservoir and varying the 
percentage of dam surface destruction. Most conclusions are drawn from the case where 
the lake is at its maximum level of 330m and 26% of the dam is destroyed; while larger 
break percentages don’t show siginficant differences. The focus of this study is the time-
evolution and the characteristics of the flood wave and its effects on the population on the 
banks of the river Tigris. 

Our calculations show the following: 

1.  The  floodwave  will  reach  the  city  of  Mosul  in  less  than  two  hours,  it  will  attain 
heights of more than 20m in around 3hours 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 floodwave of more than 10m, thus risking 
complete annihilation. 

2.  The  water  wil  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 floodwaves  of more 
than 5 metres in height. An area of 7 200 square km would be inundated, with a 
huge economic and social cost. 

3.  According to these simulations, in the case of Mosul, an evacuation within 4 to 5 

km from the river would be advisable. 

4.  Our results are in good agreement with results of previous studies. Here we add a 
detailed time profile of the floodwave’s height and an up-to-date estimate of the 
affected  population  using  GIS.  We  also  provide  detailed  maps  of  the  potentially 
affected cities. 

5.  The  analysis  of  the  presence  of  the  connecting  channel  between  Samarra  and 
Thartar lake indicates that the maximum relief flow through this channel (that was 
not  initially  considered),  does  not  have  a  significant  influence;  the  inundation  of 
Baghdad takes place approximately at the same extent with or without the channel.  

Further analyses have been performed by varying the initial lake height in order to identify 
the  effect  of  the  lake  height  reduction  on  the  maximum  flow  depth  and  the  extent  of 
inundation  and  affected  population.  The  results  show  that  the  lake  height  reduction 
plays  a  very  important  role  in  the  reduction  of  both  quantities  and  also  in  the 
times  elongation  so  that  more  time  is  available  for  the  population  to  evacuate 
from  the  possibly  affected  areas:  as  a  matter  of  fact  the  arrival  time  in  Bagdhad 
increases from 3 to 6 days by reducing the lake height from 330 to 300 m with obvious 
improvements in the possible consequences. 

38 

 
 
 
 
 
 
 
6  Limitations and Uncertainties in this study 

There are a number of factors that can influence the numerical results and the conclusions 
of  this  study.  These  should  always  be  kept  in  mind  when  considering  the  results,  and 
especially if life-or-death decisions are to be taken based on them. Uncertainties and errors 
can be introduced by the following factors. 

1.  Errors in the elevation data and low resolution of the ground topography: In this 
study  we  used  ground  data  of  180m  resolution  that  can  “smooth  out”  particular 
ground features. This can also affect the times and depths reported for the flood 
wave. The authors expect to be able to run simulations of higher resolution (that 
are quite time-consuming) in the near future. 

2.  Errors in the data and changes in the population numbers: In the first draft of this 
study we used the population data of LANDSCAN 2014 with a rather low resolution 
of around 1 km2 and we continued using this set for consistency. More importantly, 
this  data  set  cannot  possibly  take  into  account  recent  population  movements 
caused by warfare. The population data we give should be considered under these 
restrictions.  Future  modelling  would  use  more  detailed  population  data  sets 
recently made available, such as the Global Human Settlement Layer (GHSL). 
3.  Modelling  of  the  dam  failure:  As  mentioned in  the  text,  these  simulations  model 
the dam break to be almost instantaneous; it might be more realistic to introduce 
a gradual failure, as has been done in other studies. This would lower the maximum 
flood-wave  height  and  the  arrival  time  of  this  maximum  (but  would  have  lesser 
effects on the inundation extent). It is not the intention of this study to model the 
dam break with precision, but rather to estimate the affected population in a rapid-
assessment manner. 

4.  The lake bathymetry was deduced by digitising a raster image in the study of Issa 
(2015). A more precise bathymetry would render the water volumes and the flow-
out times more accurate. 

5.  The modelling of the connecting channel between Samarra and the Lake should be 
done by including the right dimensions whcih are not well known at the moment.  

39 

 
 
 
 
 
 
References 

1.  Al-Ansari, Adamo, Issa, Sissakian, Knutsson, “Mystery of Mosul Dam the Most Dangerous Dam 
in the World: Dam Failure and its Consequences”, Journal of Earth Science and Geotechnical 
Engineering, Vol. 5 no. 3, 2015, 95-111. 

2.  Kelley, Wakeley, Broadfoot, Pearson, McGill, Jorgeson, Talbot, McGrath, “Geologic Setting of 
Mosul Dam and its Engineering Implications”, Final Report, US Army Corps of Engineers, ERDC 
TR-07-10, September 2007 

3.  The  Guardian,  2  Mar  2016,  http://www.theguardian.com/world/2016/mar/02/mosul-dam-

4. 

engineers-warn-it-could-fail-at-any-time-killing-1m-people  
Iraq Business News, 3 Mar 2016, http://www.iraq-businessnews.com/2016/03/03/iraq-signs-
contract-with-italian-firm-to-consolidate-mosul-dam/ 
Iraqi Ministry of Water Resources: http://www.mowr.gov.iq/ar/node/75 

5. 
6.  The  Guardian,  29  Feb  2016,  “Iraqi  PM  and  US  issue  warnings  over  threat  of  Mosul  dam 
collapse”,  http://www.theguardian.com/world/2016/feb/29/iraq-us-issue-warnings-threat-
of-mosul-dam-collapse 

7.  G.  Franchello,  E.  Krausmann  -  'HyFlux2:  a  numerical  model  for  the  impact  assessment  of 
severe inundation scenario to chemical facilities and downstream environment' - EUR 23354 
EN – 2008 

8.  Elias  Issa  –  ‘Sedimentological  and  Hydrological  Investigation  of  Mosul  Dam  Reservoir’  – 

Doctoral Thesis - Luleå University of Technology, 2015 

9.  Hojas-Gascon,  Bianchi,  Alfieri,  Dottori,  Salamon,  JRC/ERCC  report,  4/3/2016,  private 

communication. K 

10. Thair M. Al-Taiee 1 and Anass M. M. Rasheed – “Simulation Tigris River Flood Wave in Mosul 
City due to a Hypothetical Mosul Dam Break”  - Thirteenth International Water Technology 
Conference, IWTC 13 2009, Hurghada, Egypt 

Acknowledgements 

The authors would like to thank Giovanni Franchello for his help with setting up the Hyflux2 code and 
Andrea Gerhardinger for the digitalisation of the bathymetry maps and general GIS support. 

40 

 
 
 
 
 
 
 
 
 
List of figures 

Figure 1: The dam of Mosul (Google Earth, 2010) ..................................................... 5 

Figure 2: Lake bathymetry (from Issa 2015) ............................................................ 7 

Figure 3: Dam breach profile .................................................................................. 9 

Figure 4: Dam breach representation ....................................................................... 9 

Figure 5: Time evolution maps of the water flow. .................................................... 11 

Figure 6: Overview map of water flow and travel time ............................................. 12 

Figure 7: Water height versus time for the lake and for the major cities downstream. . 13 

Figure 8: Dam failure profiles for the different scenarios run. The dam is seen face-on. 42 

Figure 9: Height-Depth graph  for the lake, for the three scenarios: 7% damage (blue), 
26% damage (brown), 60% damage (red) ............................................................. 43 

Figure 10: Height-Time graph for Mosul, for the three scenarios: 7% damage (blue), 26% 
damage (brown), 60% damage (red)..................................................................... 43 

Figure 11: Height-Time graph for Baghdad, for the three scenarios: 7% damage (blue), 
26% damage (brown), 60% damage (red) ............................................................. 44 

Figure  12:  Comparison  of  the  inundation  maps  for  two  scenarios:  7%  (blue)  and  26% 
damage (orange area). ........................................................................................ 45 

41 

 
 
 
 
 
7% Case 

Only the 
upper 
part of 
the dam 
is broken 
for a 
length of 
about 
500 m 

26% 
deep 

The dam 
is broken 
down to 
the 
bottom 
but to a 
limited 
horizontal 
extent 

60% 
deep 

The dam 
is largely 
broken all 
the way 
to the 
bottom 
part 

7  Appendix I: Different scenarios of dam failure 

Figure 8: Dam failure profiles for the different scenarios run. The dam is seen face-on. 

42 

 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 9: Height-Depth graph for the lake, for the three scenarios: 7% damage (blue), 26% damage 
(brown), 60% damage (red) 

Figure 10: Height-Time graph for Mosul, for the three scenarios: 7% damage (blue), 26% damage 
(brown), 60% damage (red) 

43 

 
 
 
 
 
 
 
Figure  11:  Height-Time  graph  for  Baghdad,  for  the  three  scenarios:  7%  damage  (blue),  26% 
damage (brown), 60% damage (red) 

7% break  26% break  60% break 

ORIGINAL LAKE VOLUME 
(km3) 

9.6  

9.6 

Residual Volume After Break 

3.2 

LOST WATER VOLUME 

6.4 

0.5 

9.1 

9.6 

0.5 

9.1 

The table above shows that the final amount of water expelled in the 28 and 60% cases is the same, 
while the one with 7% is 30% less; the emptying time is  also much longer and this explains the 
much smaller dynamic and final height in Baghdad. 

44 

 
 
 
 
 
 
 
 
  
 
Figure  12:  Comparison  of  the  inundation  maps  for  two  scenarios:  7%  (blue)  and  26%  damage 
(orange area). 

45 

 
 
 
 
 
46 

 
 
 
 
 
8  Appendix II: Inundation maps of major cities 

These maps show the flood wave height contours superimposed on maps of the cities. All 
maps in this Appendix use the results of the 26% damage scenario with the maximum 
initial level of the lake, 330m. Background data were extracted from OpenStreetMap 
(OSM). We used the city’s streets and (where enough data were available) the land-use 
classification to indicate the approximate extent of the inhabited urban areas. As inhabited 
areas (shown in light grey) we used the following classes of OSM: Residential, Commercial, 
Industrial, Military, Cemetery. In places where the flood wave colours overshadow those 
of the urban areas, one could consider the existence of city-like streets as a rough indicator 
of inhabited areas. 

47 

 
 
 
 
2 

 
 
 
3 

 
 
 
9  Appendix III – Maps related to Lake Level Sensitivity Analysis 

In this Appendix we show maps of the expected inundation in Baghdad, depending on the 
level of the lake when  the breach occurs; as previously, the levels considered are 300, 
305, 307, 309, 319 (current level) and 330m (maximum level). 

Initial Lake 
level: 300m 

Initial Lake 
level: 305m 

4 

 
 
 
Initial Lake 
level: 307m 

Initial Lake 
level: 309m 

5 

 
 
 
Initial Lake 
level: 319m 

Initial Lake 
level: 330m 

6 

 
 
 
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