6TH INTERNATIONAL CONFERENCE ON DAM ENGINEERING C.Pina, E.Portela, J.Gomes (ed.) Lisbon, Portugal, February 15-17, 2011 INTERNAL EMERGENCY ACTION PLANS FOR DAMS – APPLICATION TO THE ODELOUCA EARTHEN DAM Mário J. Franca, Ana Quintela *, Miguel Gamboa †, Carla Cupido, Marisa Viriato, João Sousa ‡ and Rui M.L. Ferreira § * Tetraplano, Engenharia Lda Rua Poeta do Bocage, n.º 13 – B, 1600-581 Lisbon, Portugal e-mail: [email protected], webpage: http://www.tetraplano.com Keywords: dam safety, internal emergency action plan, dam break modeling Abstract . Portuguese regulation classifies large dams in three classes according to the risk in the downstream valley. To Class 1 dams, corresponding to the maximum risk, an Internal Emergency action Plan (IEP) relative to the reservoir and to the near area of the downstream valley is demanded to dam owners. The information contained in the IEP constitutes the main guidelines to dam owner when facing adverse situations which may cause consequences to the dam itself and to the downstream valley. Odelouca dam in Algarve, recently built, is a 76 m high earthen dam with a storage volume of 157 hm 3. An internal emergency plan was established to the first 17 km downstream the dam where about 110 persons lives. The elaboration of IEP for Odelouca dam followed novel directives from national civil protection authorities and it was based on two important premises: i) an adequate valley characterization based on an intensive valley survey and, ii) a solid numerical simulation of flood in case of dam break made with up-to-date physical based breaching and wave propagating models, RoDaB and STAV. In the present communication we present the key directives followed in the valley survey, the numerical modeling of the dam breaching and consequent flood, extracts of the flood risk maps and the main features of the action plan. 1 INTRODUCTION The presence of a dam induces an additional risk in the valley due to the immense destructive potential of the volume of water stored in the reservoir. Although associated to a low probability of occurrence, the devastating consequences justify the concerns of the authorities and the amount of research still performed on dam accidents modeling (i.e. actions led by ICOLD - International Committee On Large Dams and such other research workgroups as CADAM 20001, RESCDAM 2001 2 and IMPACT 2005 3). Relevant guidelines and legislation have been produced in Europe and USA as a result of the increasing focus on dam safety issues led by national institutions (cf. Rodrigues et al . 2002 4, Dinçergök 2007 5 and Wieland and Mueller 2008 6). † Private Consultant, Lisbon, Portugal ‡ Águas do Algarve, Faro, Portugal § CEHIDRO & Instituto Superior Técnico, T.U. Lisboa, Av. Rovisco Pais, Lisbon, Portugal 1 Mário Franca, Ana Quintela, Miguel Gamboa, Carla Cupido, Marisa Viriato, João Sousa and Rui Ferreira In 1990, Portuguese regulation imposed dam break studies to all new and existing structures including the execution of flooding maps. New Portuguese Dam Safety Regulation, published in 2007, imposes the classification of dams in three classes according to the effective risk in the downstream valley, namely in what concerns life loss and damage due to a dam break originated flood wave (Pinheiro et al ., 2010 7). To Class 1 dams, corresponding to the maximum risk, an Internal Emergency action Plan (IEP) is demanded to dam owners to be implemented under the supervision of national Authority for dams (Instituto da Água, I.P. – INAG). The main objective of an IEP is to frame and guide the actions to be taken by dam owners facing adverse situations which may cause consequences to the dam itself and to the downstream valley (INAG, 2001 8). The previewed actions must warrant an efficient human response under difficult and stressing situations. IEP contemplates preparedness to flood situations related to dam break accidents or resulting from extraordinary natural floods through the spillway. Although the recent guidelines (ANPC & INAG, 2009 9) and publications (Viseu and Silva, 2004 10 and Viseu & Almeida, 2001 11 ) defining the general outline of a dam IEP, no definite paradigm exists in Portugal yet (for instance, a model is advised by US Interagency Committee On Dam Safety to assure consistency and uniformity of dams IEPs). Dams IEPs include aspects related to the safety of the dam itself, of the reservoir and of the near area of the downstream valley, where no external means of rescue are considered and the safety of the people depend on their own preparedness and on an adequate warning system (herein called self-awareness area), contributing to the efficacy of dam emergency planning (Viseu & Almeida, 2001 11 ). The responsible for the implementation of the IEP is the dam owner, namely the so-called IEP Director. According to national civil protection guidelines, the downstream section of this near area corresponds either to the distance travelled by the dam break wave during 30 minutes or to the downstream distance of 5 km to the dam (ANPC & INAG, 2009 9). Figure 1: Odelouca dam under construction in the spring of 2009 – upstream slope. In the present communication we present the general guidelines and the main aspects followed during the completion of the Internal Emergency action Plan of Odelouca dam (cf. Franca et al ., 2010 12 , Gamboa et al ., 2010 13 and Ferreira et al . 2010 14 ). Odelouca dam (Fig. 1), in Algarve, is a 76 m high earthen dam with a storage volume of 157 hm 3. Given the occupation of the valley the dam was classified as Class 1 and subjected to IEP. An internal emergency plan was established to the first 17 km downstream the dam where about 110 persons lives. The elaboration of IEP for Odelouca dam followed novel 2 Mário Franca, Ana Quintela, Miguel Gamboa, Carla Cupido, Marisa Viriato, João Sousa and Rui Ferreira directives from national civil protection authorities and it was based on two important premises: i) an adequate valley characterization based on an intensive valley survey and, ii) a solid numerical simulation of flood in case of dam break made with up-to-date physical based breaching and wave propagating models. The dambreak flood propagation included the estuary of river Arade and an important river confluence where extra modeling complexities exist. The plan was established, implemented in the field and approved by the Authority in 2009 and may be considered a state of the art IEP, following the most recent national and international directives. Following the present introduction, the structure of the plan is presented. Subsequently, the main guidelines followed in the valley characterization are described. The numerical modeling of the dam break flood is then explained which was based on breaching and wave propagating models, RoDaB and STAV. The methodology to implementation of the flooding map is described as well as the spatial range of the IEP and the dam classification as a function of the risk downstream the dam. The main guidelines of the action plan are described with examples and the warning system is briefly presented. Finally, the mains highlights of the plan are drawn. 2 STRUCTURE OF THE PLAN The structure of the Internal Emergency action Plan for Odelouca dam followed the indication of Portuguese regulation and included three volumes (cf. Fig. 2): i) the main text where an explanation and justification of the options adopted are given, ii) one appendix with data used on the elaboration of the plan and, finally iii) one operational appendix where the main criteria, actions and responses are defined. Figure 2: Organization of the Internal Emergency action Plan for Odelouca dam. The main text contains four sections: framework (1), where the IEP is contextualized within regional and national authorities, the main responsibilities are established, the dam, catchment basin, reservoir and valley are characterized, the monitoring system of the dam is described and the modeling leading to the dam break flood definition is explained; action plan (2), where the emergency levels criteria, the command chain, the anomalies detection and consequent response are described; warning system (3), where its operational features are described; and, one section devoted to plan management (4), including implementation, continuous assessment, maintenance and updating. 3 Mário Franca, Ana Quintela, Miguel Gamboa, Carla Cupido, Marisa Viriato, João Sousa and Rui Ferreira The so-called data appendix contains a photographic survey (A1) of the main features of the dam and valley, a file with the main dam characteristics (A2), the output from dam break modeling (A3), characterizing files (A4) to all the edification in the near-valley area within the IEP influence and the field survey (A5) with the main physical characteristics of the valley concerning flood modeling purposes. The operational appendix contains notification and interaction diagrams (A6) between the elements on the plan, a list of criteria (A7) pertaining the decision on the emergency level, a list of the preventive and mitigating actions (A8) concerning possible anomalies, the contacts of the elements of the plan (A9), a list of means and resources (A10) belonging to the dam owner, including their description and location, that may be used on emergency, the description of the warning system (A11), the contacts of the inhabitants within the valley (A12) that are affected by the potential flood, templates to notification reports (A13) and emergency declarations (A14). The main body text and the first appendix contain data useful to understand the plan and to comprehend the options made on this, whereas the operational appendix represents the main document to be used under emergency situations containing the most useful and practical information. Two maps are part of IEP, one containing the location of the dam and downstream valley regional on a national and regional context, and a second one containing the inundation map in case of dam break and the implementation of the equipment of the warning system in the downstream valley.