Safety Science 48 (2010) 1351–1360

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Safety Science

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Learning from Tabasco’s floods by applying MORT

Jaime Santos-Reyes *, Rafael Alvarado-Corona, Samuel Olmos-PeñaGrupo: ‘‘Seguridad, Análisis de Riesgos, Accidentes y Confiabilidad de Sistemas” (SARACS), SEPI-ESIME, IPN, Edif. 5, 2o. Piso, U.P. ‘‘Adolfo Lópes Mateos”, 07738 D.F. México, Mexico

a r t i c l e i n f o

Article history:Received 3 August 2009Received in revised form 8 April 2010Accepted 14 May 2010

Keywords:FloodingMORTNatural disastersTabasco

0925-7535/$ - see front matter � 2010 Elsevier Ltd. Adoi:10.1016/j.ssci.2010.05.008

* Corresponding author. Tel.: +52 55 5729657296000x54588.

E-mail address: jrsantosr@hotmail.com (J. Santos-R

a b s t r a c t

Natural disasters are increasing alarmingly worldwide in recent years. They have killed millions of peo-ple, and adversely affected the life of at least one billion people. Given this, natural disasters present agreat challenge to society today concerning how they are to be mitigated so as to produce an acceptablerisk is a question which has come to the fore in dramatic ways recently. In 2007, the state of Tabasco,Mexico, was flooded and it is believed that al least one million people were left homeless. The paperaddresses the following question: what can be learnt from flood disasters? The paper presents some pre-liminary results of the analysis of the Tabasco’s flooding by applying the Management Oversight Risk Tree(MORT). The MORT technique may be regarded as a structured checklist in the form of a complex ‘fault-tree’ model that is intended to ensure that all aspects of an organization’s management are looked intowhen assessing the possible causes of an incident. One of the key conclusions of the present analysis isthat the approach to decision making in relation ‘flood management’ at the time of the disaster has notbeen based explicitly on ‘flood risk assessment’. It is hoped that by conducting such analysis lessons canbe learnt so that the impact of natural disasters such as the Tabasco’s flooding can be mitigated in thefuture.

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1. Introduction

1.1. Flood disasters

Natural disasters are increasing alarmingly worldwide. Floodingis a common natural disaster which very often causes property andhuman losses. Recent flooding disasters have shown the vulnerabil-ity of the so called developed and developing countries to suchevents. On 26 December 2004 a quake triggered a tsunami; i.e. aseries of large waves that spread thousands of kilometres over sev-eral hours; for example, in Kalutara (a tourist resort in Sri Lanka) thewater reached at least 1 km inland, causing widespread destructionand death (UNDP, 2005). Similarly, the flooding in the United Statesafter hurricane Katrina in August 2005 has illustrated the destruc-tive nature of flood disasters. The disaster caused an enormous eco-nomic damage in the states of Louisiana and Mississippi; it isbelieved that a total of $90 billion have been estimated as the dam-ages associated with this event (USACE, 2006). Moreover, the city ofNew Orleans was severely affected with an estimated economicaldamages to residential property and public infrastructures (i.e.roads, railroads, water defences, electricity network, drainage,etc.) at US$16 billion and US$7 billion, respectively (IPET, 2007). Itis believed that a year after the disaster, New Orleans has got

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eyes).

merely a half of its population back and about 66% two years afterthe disaster (Liu et al., 2006). On the other hand, Europe has been hitby severe and repeated flooding; for instance the flooding on theOder River in 1997 which caused the evacuation of 162,000 people(Kundzewicz, 1999). Flooding on the Elbe River in 2002 caused anestimated $12 billion in damages in Germany and the Czech Repub-lic (Becker and Grunewald, 2003). McCarthy et al. (2007) argue thatmore than £200 billion worth of property and infrastructure, andover 4 million people, are at risk from flooding around Britain’s riv-ers and coasts and in towns and cities.

On the other hand, the International Federation of Red CrescentSocieties (IFRCS) published a report and concluded that in the10 years to 2006, there were a total of 1486 flood disasters, affectingall five continents. The highest number was in Asia (547 flood disas-ters) and the lowest, Oceania (43 flood disasters) (IFRCS, 1998,2008). On the other hand, there is evidence that there will be anincreasing trend towards more frequent and intense ‘‘precipitationevents’’. For example, The International Panel on Climate Change(IPCC) concluded that there was a 90–99% probability that suchincreased, heavy rainfalls worldwide will result in damage toecosystems and the loss of agricultural systems that support foodproduction, destruction of the built environment, industrial andtransport infrastructures, loss of human settlements, adverse effectson ground and surface water catchments, poor sanitation and drink-ing water quality (IPCC, 2007; Parry et al., 2007). Similarly, dramaticincrease in flood frequency and intensity are also likely to occur inEurope and the U.S. (Schröter et al., 2005; Gleick, 1999).

1352 J. Santos-Reyes et al. / Safety Science 48 (2010) 1351–1360

1.2. Accident analysis in socio-technical systems

Accidents may be regarded as unplanned and unintentionalevents that result in the loss of human life, property, production,etc. (Gavious et al., 2009; LaBelle, 2000). Moreover, these losses in-crease an organization’s operating costs, decrease efficiency, andsome undesirable long term effects such as an unfavourable publicopinion (Cullen, 1990). On the other hand, there are not singlecauses of such events but involve multiple and interrelated causalfactors. Given this, it may be argued that accident analysis’ purposeis to understand why the accident happed so that lessons can belearned and consequently prevent recurrence in the future. A num-ber of accident tools have been developed to addressed this; see forexample, PRISMA (van der Schaaf, 1996); STAMP (Leveson, 2004);MORT (Johnson, 1980); Accimap (Rasmussen, 1997; Hopkins,2000); see also Hale et al. (1997). It may be argued that accidentanalysis tools are intended to help to identify ‘root causes’ of acci-dents so that lessons can be learnt and prevent recurrence; thisraises questions such as what may be regarded as a ‘root cause’,or a ‘causal factor’. Some authors, such as Johnson (2003) has ad-dressed this by proposing some useful causal concepts based onearly works on causation by Lewis (1973, 1986) and Mackie(1993). For example, Lewis argues that necessary causal factorscan be distinguished using a particular form of ‘counterfactual’ rea-soning; i.e. ‘‘If A and B are states or events, then A is a necessarycausal factor of B if and only if it is the case that If A had not oc-curred then B would not have occurred either” (Johnson, 2003).On the other hand, Mackie argues that a single cause is non-redun-dant factor which forms part of a more elaborate ‘causal complex’;however, it is the conjunction of singular causes within the causalcomplex that that leads to an event (Johnson, 2003). Johnson sum-marizes the two approaches as ‘‘Lewis’ work focuses on more nar-rowly on necessary causal factors while Mackie’s work on causalcomplex focuses on conditions that are sufficient for an outcomebut which are not necessary”. Johnson has proposed three classesof causal factors in the context given above, namely: ‘‘contextualfactors”, ‘‘contributory factors” and ‘‘root causes”. ‘‘Contextual fac-tors” have been defined, by the author, as ‘‘neither necessary norsufficient”, events that did not directly contribute to accidents;‘‘contributory factors”, on the other hand, have been defined as,‘‘necessary but not sufficient”, events that collectively increasethe likelihood of an accident but that individually would not ledto an undesirable outcome. Finally, the author argues that a ‘‘rootcause” (‘‘necessary and sufficient”) captures Lewis’ notion of causa-tion; i.e. if the ‘root cause’ had not occurred in the singular causesof an accident then the accident would not have occurred. Theseconcepts may be relevant for the present case study; however,for a full discussion about these concepts, see the references given.

Given the above, natural disasters present a great challenge tosociety today concerning how they are to be mitigated so as to pro-duce an acceptable risk is a question which has come to the fore indramatic ways in recent years. This paper addresses the followingquestion: what can be learnt from flooding disasters? The paper pre-sents some preliminary results of the application of the Manage-ment Oversight Risk Tree (MORT) technique to the case of theTabasco flood disaster. The disaster occurred in 2007, in the stateof Tabasco, Mexico; it is believed the floods left al least one millionpeople homeless and over 3000 million US Dollars in economicallosses. (CEPAL/CENAPRED, 2008).

The paper is organized as follows: a brief description of thegeography, hydrology of the state of Tabasco as well as the se-quence of the main events leading to the disaster is presented inSection 2. Section 3, on the other hand, describes the MORT tech-nique. The application of the MORT to the case study is presentedin Section 4. Finally, some discussion and conclusions are pre-sented in Section 5.

2. The state of Tabasco and the disaster

2.1. Geography and hydrology

The State of Tabasco is located at the Southern region of Mexico(see Fig. 1). The state is bordered by three states; i.e. Veracruz tothe west; Chiapas to the south; and Campeche to the north-east.Moreover, Tabasco borders to the east with Guatemala and to thenorth with the Gulf of Mexico. Tabasco’s capital city is ‘‘Villaher-mosa”. On the other hand, the hydrology of Tabasco is a complexnetwork of rivers, lagoons and streams. The Mexican’s two biggestrivers ‘‘Grijalva” and ‘‘Usumacinta” flow through the state; both ofthem converge before draining into the Gulf of Mexico. The volumeof water between the two is about 125 thousand millions of cubicmeters of water and this represents 35% of the total amount ofwater of all the rivers in the country. (Tabasco, 2008).

2.2. The flooding

The disaster occurred in November 2007 and it has been re-garded as one of the worst that has hit the state for more than50 years. It is believed that 80% of the state has been flooded andmore than one million people have been left homeless.

2.2.1. The contextIn order to facilitate the description and discussion of the find-

ings of the present paper, a brief description of some of the keyorganizations involved in the ‘disaster risk management’ is givenin the subsequent paragraphs.

The CFE is a company that provides all the services involve inpower generation, transmission and distribution across Mexico. Itprovides electricity to 26.7 million customers, nearly 80 millionMexicans (CFE, 2009). CFE was (still is) in charged of a hydroelec-tric plant in Tabasco. In general, a hydropower plant captures theenergy of falling water to generate electricity. It should be pointedout that most hydroelectric plant includes four major components:(1) a Dam (i.e., ‘‘Peñitas” is the name given to the Dam which is lo-cated a few kilometres from the capital city) which raises the waterlevel of the river to create ‘falling water’. Also, it controls the flowof water; (2) turbine; (3) generator and (4) transmission lines.

On the other hand, the National Water Commission (CONAGUA)is an agency of the Ministry of the Environment and Natural Re-sources (SEMARNAT) of the Mexican Government. CONAGUA’smain tasks are: the administration of the National Waters; theManagement and control of the hydrologic system, and the promo-tion of social development (CONAGUA, 2009). In 2003, CONAGUAand the state government of Tabasco agree on a joint ‘‘Flood Con-trol” (PICI) project. The PICI project was intended to prevent futurefloods in the Capital City of Tabasco. It is believed that over twothousand million Mexican pesos (151,000,000 USD) was allocatedto the project (Patterson, 2007). Moreover, the project was plannedto conclude by May 2006.

2.2.2. The key events of the floodingThe sequence of the main events is thought to be the following:

October 28th, 2007

The rise of the main rivers’ levels that flow a cross the state of Ta-basco have been detected. This has been caused by a heavy rain(136 mm) and the deficiencies or inadequacy of the operationalmodes of the hydroelectric system (i.e., overflow of the ‘‘Peñitas”dam) located nearby the capital city of Tabasco; this might have con-tributed to the rise of the rivers’ levels. It is believed the rise of theriver levels has affected some of the municipalities of the state.

Fig. 1. The state of Tabasco, Mexico.

J. Santos-Reyes et al. / Safety Science 48 (2010) 1351–1360 1353

As a consequence of the above, some 135,000 people were af-fected and some shelters have been made available for the affectedpeople. It is believed the shelters have been installed in some of themunicipalities of the state.

October 29th, 2007

The CFE informs that water from the ‘‘Peñitas” dam has beendischarged and it is believed that about 1500 m3/s has been re-leased on Monday 29 October. This caused an increase for abouta meter (1 m) above the Grijalva river’s level.

Given the above, the local authorities requested the population tobuild physical barriers (mainly sandbags) in order to contain theflood.

Also, the evacuation of people living in the flooded areas started.The CONAGUA reports that at this stage the heavy raining still

continuing reaching levels of about 317 mm; it claimed that theselevels have not been seen for more than 50 years.

October 30th, 2007

Civil protection and the military have been working for the rein-forcement of the physical barriers that have been built (mainlysandbags) in order to contain the water from the rivers. At thisstage, it is believed the ‘‘Grijalva” river was about to overflowand that the Tabasco’s capital city (i.e. ‘‘Villahermosa”) was underthreat to be flooded.

By this time, it is thought that more than 227 school buildingshave been affected and about 44 of these have been used as shelters.

October 31st, 2007

It is believed that two rivers (i.e. ‘‘Carrizal” and ‘‘Grijalva”) over-came the physical barriers due to an increase of their flow capacity.Tabasco’s Governor announces that 70% of the state was underwater and 300,000 people have been affected. Moreover, the maineconomical activities have been halted; i.e. schools were closed;hospitals, electricity, communication systems, water supply, etc.have been affected.

November 1st, 2007

The Mexican President tours the affected area and addressedthe nation on television to report on the gravity of the situation.

Tabasco’s Governor states that ‘‘80% of the state is probably flood-ed” and gave a figure of 400,000 people being affected.

November 2nd, 2007

In the early hours in the morning, the ‘‘Grijalva” river breaks thedykes in the capital city of Villahermosa and the city’s central dis-trict is ordered to evacuate. It is believed one million homes are un-der water.

November 3rd, 2007

The army is deployed at the affected areas (i.e. supermarkets,shops, etc.) in order to protect these from looting.

November 4th, 2007

Residents have been relocated to shelters and it is believed theycomplained about the inadequacies in the distribution of aid. It isbelieved some shops and Lorries carrying aid have been looted.

November 5th, 2007

Food shortages are reported at the shelters. The Mexican presi-dent visits the area for a third time and announces a plan for thestate including the cancellation of tax payments and electricitybills. A landslide washes away 50 houses in the village of ‘‘Juandel Grijalva” on the Tabasco–Chiapas border; 70 people are re-ported missing.

November 6th, 2007

The water levels in both the ‘‘Grijalva” and the ‘‘Carrizal” riversfall significantly overnight. Pumping begins to drain the capitalcity; i.e. ‘‘Villahermosa”.

2.2.3. Summary of the consequences of the disasterOverall, the consequences of natural disasters are severe in

terms of loss of life, property and economic. It is believed that835 towns were flooded and 621 were affected indirectly as a re-sult of the flooding. These affected towns represent 58% of the totalof 2530 towns that form part of the state of Tabasco (see Fig. 2).

The economical damages are being reported to be 31,871 mil-lions of Mexican Pesos (over 3000 million US Dollars). Table 1and Fig. 3 show some details of the economical losses.

Indirected affected towns

(including urban and country

areas), 621

Flooded towns (including urban

and country areas),

835

Fig. 2. Affected towns by the floods (CEPAL/CENAPRED, 2008).

Table 1Summary of the affected industry sectors (CEPAL/CENAPRED, 2008).

(a) It is believed hat 1.2 million of people have been affected.(b) 6500 km of roads and paths were affected.(c) 132 Bridges.(d) 570,000 hectares of agricultural and livestock have been affected.(e) 31,871.26 in damages to the main productive sectors; see Fig. 3 for details

about these.

1354 J. Santos-Reyes et al. / Safety Science 48 (2010) 1351–1360

3. The Management Oversight Risk Tree (MORT)

The Management Oversight and Risk Tree (MORT) is an analyt-ical procedure for determining causes and contributing factors. InMORT, accidents are defined as ‘‘unplanned events that produceharm or damage, that is, losses” (NRI-1, 2002). Losses occur whena harmful agent comes into contact with a person or asset. Thiscontact can occur either because of a failure of prevention or, asan unfortunate but acceptable outcome of a risk that has beenproperly assessed and acted-on (a so-called ‘‘assumed risk”). MORTanalysis always evaluates the ‘‘failure” route before considering the‘‘assumed risk” hypothesis. In MORT analysis, most of the effort isdirected at identifying problems in the control of a work/processand deficiencies in the protective barriers associated with it. Theseproblems are then analyzed for their origins in planning, design,policy, etc. In order to use MORT key episodes in the sequence of

Social sector, 18.74%

Small businesses15.00%

Environment, 0.51%

Infrastructure sector (roads, ports, energy, etc.), 17.83%

Fig. 3. Economical losses (CE

events should be identified first; each episode can be characterizedas: {a} a vulnerable target exposed to; {b} an agent of harm in the;{c} absence of adequate barriers. The ‘‘Barrier analysis” is intendedto produce a clear set of episodes for MORT analysis. It is an essen-tial preparation for MORT analysis. The barrier analysis embracesthree key concepts, namely: {a} ‘‘energy”; {b} ‘‘target”; and {c}‘‘barrier”. ‘‘Energy” refers to the harmful agent that threatens oractually damages a ‘‘Target” that is exposed to it. ‘‘Targets” canbe people, things or processes – anything, in fact, that should beprotected or would be better undisturbed by the ‘‘Energy”. InMORT, an incident can result either from exposure to an energyflow without injuries or damage, or the damage of a target withno intrinsic value.

Fig. 4 shows the basic MORT structure. The top event in MORT islabelled ‘‘Losses”, beneath which are its two alternative causes; i.e.,{1} ‘‘S/M-Oversights and Omissions”, {2} ‘‘R-Assumed risks”. InMORT all the contributing factors in the accident sequence aretreated as ‘‘oversights and omissions” unless they are transferredto the ‘‘Assumed risk” branch. Input to the ‘‘Oversights and Omis-sions” event is through and AND logic gate. This means that prob-lems manifest in the specific control of work activities, necessarilyinvolve issues in the management process that govern them. Onthe other hand, the ‘‘Specific Control Factors LTA” and ‘‘Manage-ment System Factors LTA” branches are regarded as the two mainbranches in MORT (see Fig. 4). ‘‘Specific control factors”, on theother hand, are broken down into two main classes: {a} those re-

Other sectors (Manufacturing,Turism, Services),

33.09%

Agriculture sector, 27.96%

Emergency services, 1.72%

,

PAL/CENAPRED, 2008).

Losses, injuries, damage, performance

lost, etc.

Oversights and omissions

Specific Control

Factors LTA

Incident Stabilization & Restoration

LTA

Potentially Harmful

Condition

Vulnerable people/objects

Controls &

Barriers

S

SA1 SA2

SB1 SB2 SB3

OR

AND

OR

AND

S/M

T

Assumed risks

OR R

R1 R2 Rn Management System

Factors LTA

Risk Assess-ment & Control

System LTA

Implementation of policy

LTA

Policy LTA

M

MA1 MA2 MA3

OR

WHAT Happened?

WHY It happened?

Fig. 4. The basic MORT structure. (Adapted from NRI-1 (2002).)

J. Santos-Reyes et al. / Safety Science 48 (2010) 1351–1360 1355

lated to the incident or accident (SA1) and {b} those related torestoring control following an accident (SA2). Both of them are un-der an OR logic gate because either can be a cause of losses.

In summary, the process of analysis consists by addressing whathappened?-branch of the MORT tree; this process is then followedby searching for causal explanations in the why-it happened?-branch. The process what?-why? is achieved by a number of ques-tions provided by the MORT user manual (NRI-1, 2002). For exam-ple the following question can be asked in order to assess theadequacy of the internal communication:

SD1-a1-b2-c3-d7:

‘‘Was the definition of the internal communication networkadequate?” (NRI-1, 2002).(The ‘SD1-a1-b2-c3-d7’ corresponds to ‘‘Network definitionLTA” under the sub-branch ‘‘internal communication”. LTAmeans ‘‘Less Than Adequate”; see Fig. 6).

4. The analysis of the disaster

A colour code has been used to conduct the analysis; i.e. if anevent was considered to be deficient or ‘‘Less Than Adequate-LTA”,then it was marked ‘red’; an event that is ‘satisfactory’ was markedgreen. On the other hand, if an issue is considered to be relevantbut there is not enough information to assess it, then this wasmarked blue. The results of the analysis of the flood disaster areshown in Tables 2 and 3 and Fig. 5–7, on the other hand, showsome examples of the MORT branches.

5. Discussion and future work

5.1. Discussion

Floods may be ranked as the highest amongst natural disastersin recent years. For example, the US Federal Emergency Manage-

ment Agency (FEMA) has regarded flooding as ‘‘America’s No. 1natural hazard” (FEMA, 2004). Moreover, the recent floods in Brazil(BBC, 2010) which has killed over 100 people have demonstratedthe need to mitigate the impact of these events. The present paperargues that by analysing past flood disasters lessons can be learntso that the impact of similar events can be mitigated. In what fol-lows some discussion, comments, conclusions and future work isgiven.

5.1.1. The approach to the analysis of the flood disasterThe present paper addresses the following question: What can

be learnt from flood disasters? In order to address the above ques-tion, a literature survey has been conducted in order to identifysimilar studies; however there is not evidence in the literature thataddresses the above explicitly; i.e. studies which have been con-ducted by applying accident analysis techniques to flood disasters.On the other hand, there has been an important development ofaccident analysis approaches to address past failure in the so calledsocio-technical systems, such as transport, nuclear, oil and gas, avi-ation. Examples of such approaches include: Accident fault trees(Petersen, 2000), PRISMA (van der Schaaf, 1996), MORT (Johnson,1980), Accimap (Rasmussen, 1997; Hopkins, 2000), etc. The MORThas been selected for the analysis of the flood disaster in the pres-ent paper. This raises the following question: why MORT? Why notother approaches? The answer to this question is straightforward:MORT has been adopted for the analysis because it has been con-sidered to be a relatively simple check list approach to causal anal-ysis. Effectively, other approaches can be applied in the future forfurther analysis of the Tabasco flood disaster (see Section 5.2 fordetails). However, some comments should be made regarding the‘methodological’ aspects of the MORT and the ‘fault tree accidentanalysis’ approaches because of their similarities; i.e. the MORTis, in essence, a fault tree. In the introduction section has beenemphasised the importance of the analysis of accidents in order

Table 2Causal factors identified on what happened?-branch of the MORT shown in Fig. 4.

Branch Description

Harmful energy (SB1) Inadequacy of flood defences to control the floods; for example the ‘hydraulic system’ to drain the city was deficient. The ‘IntegratedFlood Control Project’ (PICI) has been suspended at the time of the flood disaster and this meant that several of key infrastructurebuilding (e.g. embankments, hydraulic systems, etc.) aiming at protecting urban areas have been delayed or cancelled.

Vulnerable people/objects(SB2)

The population, property, etc. were exposed to the floods. The evacuation planning was deficient; e.g. there were not enough shelters atthe time of the flooding; inadequate evacuation routes, etc.

Controls of work and process (SC1)Information systems LTA

(SD1)Deficiencies of communication of flood warnings before and during the flooding. Residents did not know what to do during the flooding.

Deficiencies of the collection and data analysis in relation to flood risk. This may have helped to establish the nature and scale of theexisting flood risk.There was not a plan for monitoring the adequacy of the flood defences, flood warnings, evacuation procedures, etc.A flood risk assessment was not conducted before the flooding; this may have helped to identify the hazards and types of risk a floodpresents and their likely social and economical impact.

Operational readiness LTA(SD2)

The flood defences (physical and non-physical) operational readiness was not assured at the time of the flooding; for example, theexisting physical infrastructure defences (i.e. embankments, walls, weirs, sandbags, etc.) against floods, all were overtopped.Inadequacy of the flood defences at the time of the floods. That is, they were not a result of a flood risk assessment but it seems thatwere left to improvisation (e.g. sandbags).

Maintenance LTA (SD3) Deficiencies in the maintenance of the poor existing flood defences at the time of the flood disaster.Inspection LTA (SD4) Deficiencies in the inspections of the state of the flood defences (e.g. embankments, walls, weirs, hydraulic infrastructure, etc.) intended

to protect the city from flooding.

Controls of work and process (SC1)Supervision LTA (SD5) Inadequate coordination amongst the key organizations involved in dealing with flood disasters in the state of Tabasco; i.e. federal

(CONAGUA) & local governments (city and state). For example, they all failed to follow up the progress of the PICI project.The local government, local civil protection, etc. did not learn from previous floods. It is believed there have been at least three severeflooding in the region in the past; the most recent occurred in 1999.Deficiencies of flood warnings. For example, it is not clear whether the residents were warned in advance when flooding may be likelyand how severe the flooding could be. Moreover, there is no evidence that the population received practical advice on what to do before,during and after the flood, as a result of a flood risk assessment. It seems that all were left to improvisation.

Supervision Support LTA(SD6)

Lack of open and frank communication amongst the key organizations; i.e. CONAGUA and local governments (i.e. state and city). Theyblame each other of the consequences of the flood disaster.Local authorities claim that the PICI project failed to be completed because of the lack of resources. However, it is believed the moneywas mismanaged by the people in charge of the project.

Barriers LTA (SC2) There was not a real time forecasting and warning to the public before the flooding.There was not an integrated monitoring system to monitor, for example, the rainfall, river levels, etc. This information combined withdata from the National Meteorological Service (SMN), could have helped to provide local area forecasts on the possibility of flooding andits likely severity.All the flood defences (i.e. embankments, walls, weirs, sandbags, etc.) that were intended to protect the population failed to contain theflooding.Deficiencies in urbanization planning; for example, some of the physical defences were removed so that new buildings were built.

Stabilization & restorationLTA (SA2)

The local government, local civil protection, etc. did not learn from previous floods. There have been at least three severe flooding in theregion in the past being the most recent in 1999.There was not a procedure or plan directed to limiting the consequences of the flood risk. Inadequacy of the rescue and evacuation of thepopulation. It is believed that more than one million people affected by the flood disaster (equivalent to the 50% of the total populationof the State of Tabasco) could not find shelter. Moreover, it is believed that some of the shelters have been flooded during the floods.

1356 J. Santos-Reyes et al. / Safety Science 48 (2010) 1351–1360

to identify the ‘causal factors’ so that future events can be pre-vented. Also, different causal concepts based on Lewis’ and Marks’causality thinking have been introduced. Moreover, Johnson (2003)has proposed some useful concepts intended to help the analyst todistinguish ‘‘root cases” from ‘‘contributory and contextualfactors”.

Given the above, it can be argued that ‘fault trees’ approach tocausal analysis is based on a deductive logic; i.e. the analyst as-sumes a top event and then identifies the causal events relatedto the top event and the logical relations between them is achievedby the use of AND and OR gates. Moreover, it may be argued thatfault trees do not help to distinguish and identify causal factorsmentioned above; however some authors (Andrews and Moss,1993) argue that fault trees are intended to record ‘‘immediate,necessary and sufficient” events that contribute to an accident.On the other hand, it may be argued that MORT checklist approachuses some variants of counterfactual reasoning which makes it dif-ferent from the traditional ‘fault tree’ analysis (Johnson, 2003).(Next section will present a brief description of the features ofthe MORT for the present application.) However it should be

pointed out that the purpose of the present paper is to show thataccident analysis techniques such as MORT can be applied to theanalysis of natural disasters. For a detailed discussion about the‘methodological’ issues concerning ‘fault trees’ and other ap-proaches to causal analysis; see for example, Johnson (2003) andHopkins (2003).

5.1.2. Discussion on the applicationOverall, MORT addresses analysis causation by considering first

what happened and then why it happened (see Fig. 4). The ‘whathappened?’ branch of the MORT tree is intended to help to identifythe ‘barrier’ and ‘control’ problems that contributed to the unde-sired event. Once these problems have been identified, and thenthe ‘why?’-branch’ helps to identify the management factors thatcontributed to these problems. This process is achieved by the helpof a number of questions provided by the MORT user manual (NRI-1, 2002); the analyst can ask these questions as they analyse everybranch and sub-branches of the tree. Tables 2 and 3 summarise themain findings of the preset analysis. Table 2 presents the results ofwhat went wrong in the cases of the Tabasco’s flooding disaster.

Table 3Management factors on the why?-branch of the MORT shown in Fig. 5. These are thought of as the contributors to the factors identified on the what happened?-branch.

What happened? Description Why? (LTA = Less Than Adequate)

Harmful energy (SB1) Inadequacy of flood defences to control the floods; for example the ‘hydraulic system’ to drain the citywas deficient. The ‘Integrated Flood Control Project’ (PICI) has been suspended at the time of the flooddisaster and this meant that several of key infrastructure building (e.g. embankments, hydraulic systems,etc.) aiming at protecting urban areas have been delayed or cancelled.

Barrier and controls LTA

Vulnerable people(SB2)

The population, property, etc. were exposed to the floods. The evacuation planning was deficient; e.g.there were not enough shelters at the time of the flooding; inadequate evacuation routes, etc.

Hazard analysis LTA

Controls Informationsystems (SD1)

Deficiencies of communication of flood warnings before and during the flooding. Residents did not knowwhat to do during the flooding.

Hazard analysis LTA

Deficiencies of the collection and data analysis in relation to flood risk. This may have helped to establishthe nature and scale of the existing flood risk.There was not a plan for monitoring the adequacy of the flood defences, flood warnings, evacuationprocedures, etc.A flood risk assessment was not conducted before the flooding; this may have helped to identify thehazards and types of risk a flood presents and their likely social and economical impact.

Controls Operationalreadiness (SD2)

The flood defences (physical and non-physical) operational readiness was not assured at the time of theflooding; for example, the existing physical infrastructure defences (i.e. embankments, walls, weirs,sandbags, etc.) against floods, all were overtopped.

Hazard analysis LTA

Inadequacy of the flood defences at the time of the floods. That is, they were not a result of a flood riskassessment but it seems that were left to improvisation (e.g. sandbags).

Controls Maintenance(SD3)

Deficiencies in the maintenance of the poor existing flood defences at the time of the flood disaster. Maintenance plan LTA

Controls Inspection(SD4)

Deficiencies in the inspections of the state of the flood defences (e.g. embankments, walls, weirs,hydraulic infrastructure, etc.) intended to protect the city from flooding.

Inspection plan LTA

Control Supervision(SD5)

Inadequate coordination amongst the key organizations involved in dealing with flood disasters in thestate of Tabasco; i.e. federal (CONAGUA) & local governments (city and state). For example, they all failedto follow up the progress of the PICI project.

Monitoring & audit LTA

Control Supervision(SD5)

The local government, local civil protection, etc. did not learn from previous floods. It is believed therehave been at least three severe flooding in the region in the past; the most recent occurred in 1999.

Program review LTA

Control Supervision(SD5)

Deficiencies of flood warnings. For example, it is not clear whether the residents were warned in advancewhen flooding may be likely and how severe the flooding could be. Moreover, there is no evidence thatthe population received practical advice on what to do before, during and after the flood, as a result of aflood risk assessment. It seems that all were left to improvisation.

Warnings LTA

Control SupervisionSupport (SD6)

Lack of open and frank communication amongst the key organizations; i.e. CONAGUA and localgovernments (i.e. state and city). They blame each other of the consequences of the flood disaster.

Definition of line of responsibilityLTA

Control SupervisionSupport (SD6)

Local authorities claim that the PICI project failed to be completed because of the lack of resources.However, it is believed the money was mismanaged by the people in charge of the project.

Monitoring, Auditing LTA

Barriers did notprovide

There was not a real time forecasting and warning system to the public before the flooding. Barriers & controls LTA

There was not an integrated monitoring system to monitor, for example, the rainfall, river levels, etc. Thisinformation combined with data from the National Meteorological Service (SMN), could have helped toprovide local area forecasts on the possibility of flooding and its likely severity.

Barriers failed All the flood defences (i.e. embankments, walls, weirs, sandbags, etc.) that were intended to protect thepopulation failed to contain the flooding.

Inspection plans LTA

Barriers (SC2) Deficiencies in urbanization planning; for example, some of the physical defences were removed so thatnew buildings were built.

Methods, criteria analysis LTA

Stabilization &restoration (SA2)

The local government, local civil protection, etc. did not learn from previous floods. There have been atleast three severe flooding in the region in the past being the most recent in 1999.

Program review LTA

Stabilization &restoration (SA2)

There was not a procedure or plan directed to limiting the consequences of the flood risk. Inadequacy ofthe rescue and evacuation of the population. It is believed that more than one million people affected bythe flood disaster (equivalent to the 50% of the total population of the State of Tabasco) could not findshelter. Moreover, it is believed that some of the shelters have been flooded during the floods.

Contingency planning LTA &Emergency provisions LTA

J. Santos-Reyes et al. / Safety Science 48 (2010) 1351–1360 1357

5.1.2.1. What went wrong?-branch (see Fig. 4 and Table 2). In thepresent analysis, ‘‘flooding” has been taken to represent the ‘‘En-ergy” which refers to the ‘‘harmful agent” that threatens or actu-ally damages a ‘‘Target” that is exposed to it. ‘‘Targets” have beenassumed to be the population, properties, economy, etc., thatshould be protected or would be better undisturbed by the ‘‘En-ergy”. In order to address the what happened?-branch of theMORT, the analysis was conducted from top to bottom and fromleft to right; i.e. ‘‘SA1-Incident” has been considered first and thelast was ‘‘SA2-Satbilization and Restoration”. According to theMORT user manual (NRI-1, 2002), this half of the branch is in-tended to address the following: specific controls upon harmfulenergies, vulnerable people and assets; the ‘barriers’ between‘energies’, and people and assets; and how emergency actionscontributed to the final outcome. Examples of some of thebranches and sub-branches of the MORT tree for the present casestudy are given below:

SD2 Branch – ‘‘Operational readiness LTA” (LTA = Less ThanAdequate) considers the adequacy of efforts to ensure that work/

process or site was ready to be used in order to contain, for exam-ple, the flooding.

Sub-branch SD2-a2-b1 (See NRI-1,2 for details of the nomencla-ture used in the MORT tree):

‘‘Was an operational readiness check specified for this work/pro-cess?” (NRI-1, 2002).

Similarly, branch SD2-a2-b2:

‘‘Were the criteria used in the check to determine operational read-iness, adequately specified?” ‘‘Does the problem in question indi-cate inadequacies in the criteria?” (NRI-1, 2002).

And sub-branch SD2-a2-b3:

‘‘Was the required procedure for determining operational readinessadequate? Was it followed adequately?” (NRI-1, 2002).

It has been found that the flood defenses’ operational readinesswas not assured at the time of the flooding; e.g. the existing embank-ments, walls weirs, sandbags were overtopped (see Table 2).

Operational Readiness

LTA

Verification of Readiness

LTA

Compet- ence LTA

Did not Specify

Criteria LTA

Procedure LTA

Technical Support

LTA

Interface Ops/Maint & Testing

LTA

Config- uration

LTA

SD2 OR

OR

Follow-up LTA

a1 a2 a3 a4

b1 b2 b3 b4 b5

Fig. 5. SD2 Branch – ‘‘Operational readiness LTA”. (Red: problems that contributedto the outcome. Blue: need more information. Green: is judged to have beensatisfactory.) (Adapted from NRI-2 (2002).) (For interpretation of the references tocolour in this figure legend, the reader is referred to the web version of this article.)

1358 J. Santos-Reyes et al. / Safety Science 48 (2010) 1351–1360

A branch that considers the adequacy of the information sys-tems intended to support the work/process, an example of a ques-tion intended to help some issues under this branch is:

Sub-branch SD1-d5-‘‘Previous investigation and analysis LTA”:

‘‘Have there been previous similar accidents or incidents, or riskassessments of this work/process?”

‘‘Were these investigations or assessments adequate?” (NRI-1,2002).

Similarly, the branch SD-a2 – ‘‘Data collection LTA” considershow the organization captures data in relation to flood risk.According to MORT, the aim of the branch SD-a2 is not only data

TechnInforma

LTA

Knowledge LTA

SD1-a1

Based on Known

Precedent

Codes & Manuals

LTA

No Known Precedent

Prev. Al & Anal

LTA

Research LTA

Solution Research

LTA

Local Precedent

LTA

List of Experts

LTA

RO

OR OR

1b

c1 2c

d1 d3

d2 d4

d5 d6

Fig. 6. Branch SD1-a1 – ‘‘Technical information LTA”. (Red: problems that contributed(2002).) (For interpretation of the references to colour in this figure legend, the reader i

current to the problem under consideration but also the collectionof relevant data before this incident to detect problems at an earlystage (see Table 2).

SD-a2 – ‘‘Data collection LTA”: Sub-branch SD-a2-b3:

‘‘Was there an adequate plan for monitoring the work and condi-tions?” (NRI-1, 2002).

Finally, the branch ‘‘SA2 –Stabilization and restoration LTA” (seeFig. 7) has been used to assess whether actions have been pre-planned as opposed to occurring fortuitously at the time of thedisaster. For example, branch SA2-‘‘Data collection LTA”: Sub-branches SA2-a1 (‘‘Prevention of second accident LTA”) and SA2-a2 (‘‘Emergency action LTA”), examples of the guiding questionsare:

SA2-a1-b1-Plan LTA (see Fig. 7):

‘‘Was the plan for stabilization and restoration adequate?” (NRI-1,2002).

SA2-a2-c1-‘‘Training and experience LTA” (This is not shown inFig. 7):

‘‘Was the performance of people and equipment significantly differ-ent from the performance standard assumed by the plan?” (NRI-1,2002).

There have been three major floods before the 2007 flood disas-ter; however local government, local civil protection, did not learnfrom these previous floods. Moreover, there were inadequacies ofthe rescue and evacuation of the population as shown in Table 2.

5.1.2.2. Why it happened?-branch (see Fig. 4 and Table 3). As hasbeen mentioned above, the right hand side of the MORT chartshown in Fig. 4 is intended to help to find why each of the failuressummarized in Table 2 occurred. For example, in Table 2 has beenargued that, for example, there was not an integrated monitoringsystem for the rainfall, river levels, etc., this information combined

ical tion

Communication LTA

External Communication

LTA

Network Operation

LTA

Internal Communication

LTA

Network Definition

LTA

Network Operation

LTA

Network Definition

LTA

OR

RO

OR OR

2b

4c3c

d7 d8 d9 d10

to the outcome. Green: is judged to have been satisfactory.) (Adapted from NRI-2s referred to the web version of this article.)

Stabilization & Restoration

LTA

Emergency Action LTA

Prevention of Second Accident

SA2

Plan LTA

Execution of Plan LTA

OR

OR Medical Services

LTA

Dissemination of information

LTA

Dissemination of information

LTA

a1 a2

a3

a4

a5

b1 b2

Fig. 7. Branch SA2 – ‘‘Stabilization and Restoration LTA”. (Red: problems that contributed to the outcome. Green: is judge to have been satisfactorily). (Adapted from NRI-2(2002)). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

J. Santos-Reyes et al. / Safety Science 48 (2010) 1351–1360 1359

with data from the National Meteorological Service (NMS) couldhave helped to provide local area forecasts on the possibility offlooding and its likely consequences. The failure to provide such‘barriers’ can be explained in terms of the sub-branch ‘‘Barriersand Controls LTA” under the Why?-branch: ‘‘M-Management sys-tem factors LTA”: ‘‘MA3-Risk Assessment and Control System LTA”:‘‘MB1-Hazard Analysis Process LTA”: ‘‘MB1-a2-Design and Devel-opment LTA”. Similarly, the failure to learn from previous floodscan be explained in terms of the sub-branch ‘‘Definition of aimsand Policy LTA” under the Why?-branch: ‘‘M-Management systemfactors LTA”: ‘‘MB2-Program review LTA”. The other causal factorsidentified in Table 3 have been analyzed in a similar way as de-scribed above.

In order to distinguish the ‘root causes’ from the rather generalcausal factors under the why?-branch of the MORT. The analyticaltechnique proposed by Briscoe (1991) has been adopted to identifythe ‘root causes’ of the present case study. The ‘root causes’ pro-posed by Briscoe are literally represented the roots of the MORTchart and the categories are summarized in Table 4. ‘‘Bridge ele-

Table 4Example of ‘‘root causes” of the flood disaster.

Briscoe’s categories to identify‘root causes’ (Briscoe, 1991).

Management factors identified on theWhy?-branch of the MORT (see Table 3)

1. Policy

2. Policy implementation(a) Line/staff responsibility(b) Accountability(c) Vigour and example(d) Methods and criteriaanalysis

3. Bridge elements(a) Management services(b) Directives(c) Budgets(d) Information flow

4. Risk assessment(a) Safety informationsystems

(b) Hazard analysis process Barriers & controls LTAHazard analysis LTAMaintenance plan LTAInspection plan LTAWarnings LTAContingency planning LTAEmergency provisions LTA

(c) Safety programme audit

ments” are thought to represent the manner in which high levelmanagement implement safety related management policiesthroughout the various intermediate management levels withinan organization. Overall, the categories shown in Table 6 arestraightforward. (Johnson has applied the same categories to iden-tify ‘root causes’; see Johnson (2003).)

It may be argued that the causal factors that have been identi-fied by the application of the MORT technique for the present casestudy, can be broadly grouped under the ‘hazard analysis process’root cause. This may be regarded as one of the key lessons of thepresent analysis; i.e., the approach to decision making in relation‘flood management’ at the time of the disaster was not basedexplicitly on a ‘flood risk assessment’ approach; see for exampleTable 4.

5.1.3. Some other general comments

(a) It should be mentioned that some of the branches of theMORT chart were not relevant to the present case; for exam-ple the following branches and sub-braches: SD5-a5-‘‘Per-formance Errors”; SD5-a5-b3-‘‘Task Performance Errors”;SD5-a5-b3-c8-‘‘Task Assignment LTA”; SD5-a5-b3-c9-‘‘TaskSpecific Risk Assessment Not Performed”; SD5-a5-b3-c11-‘‘Task Specific Risk Assessment LTA”; SD5-a5-b3-c13-‘‘Taskprocedure did not fit with Functional Situation”; SD5-a5-b3-c14-‘‘Personnel Performance Discrepancy”; SD5-a5-b4-‘‘Non-task performance Errors”; SD5-a5-b5-‘‘EmergencyShutoff Errors”; SD5-a5-b5-c17-‘‘Task performance Errors”;SD5-a5-b5-c17-‘‘Non-performance task Errors”. However, itis too early to conclude that these and other branches ofthe MORT tree are not relevant to the analysis of naturaldisasters. Other case studies on natural disasters may beconducted so that some final comments can be made onthese. (See for example Santos-Reyes and Alvarado-Corona(2010).)

(b) It should be mentioned that some event based approaches toaccident analysis emphasises the need to reconstruct thedevelopment of an accident or incident over time. However,the MORT approach provides a checklist intended to help theanalysis to look for a number of predefined features that arecommon to a wide range of accidents; i.e. the time line of thekey events of the flood disaster given in Section 2.2.2 werenot relevant in the present case. This coincides with com-ments made about this from other authors, such as Johnson(2003).

1360 J. Santos-Reyes et al. / Safety Science 48 (2010) 1351–1360

(c) Finally, some of the limitations of the present case was thelack of reliable information about the flood disaster; forexample, information about the ‘flood risk management sys-tem’ at the time of the disaster was not available for thepresent analysis. The present case is based on the two mainreports on the flood disaster; i.e. SRCAH (2008) and CEPAL/CENAPRED (2008). (In the present analysis the branches ofthe MORT tree were coloured blue in such cases; this implyfuture investigation as the information is available.)

5.2. Conclusion and future work

Some preliminary findings of the analysis of the disaster flood ofthe state of Tabasco, Mexico, have been presented. The approachhas been the application of the Management Oversight Risk Tree(MORT) technique. A number of causal factors leading to the flooddisaster have been highlighted by the MORT. It may be argued thatmost of the causal factors identified by the application of the MORTcan be broadly grouped within the ‘hazard analysis process’ basedon Briscoe’s categories (Briscoe, 1991; Johnson, 2003). Moreover,the analysis has shown that the MORT technique (and presumablyother accident analysis techniques) has the potentiality to be usedto identify causal factors to the case of natural disasters. Further-more, it should be pointed out that the MORT has been used exten-sively to the analysis of past failures of socio-technical systems(i.e., petrochemical, transport, etc.); however this is the first timethat it has been applied to the case of natural disasters. However,more work is needed in order to draw some final lessons fromthe Tabasco flood disaster. This may be achieved by applying otheraccident analysis approaches, such as PRISMA (van der Schaaf,1996), Accimap (Rasmussen, 1997; Hopkins, 2000) and the SDMSmodel (Santos-Reyes and Beard, 2010), and others that may be rel-evant. It is hoped that by conducting such analysis lessons can belearnt so that the impact of natural disasters such as the case of Ta-basco’s flooding can be prevented or mitigated in the future.

Acknowledgements

This project was funded by SIP-IPN under the following grant:SIP-IPN, No.: 20101302.

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