SMALL DAMS PETITS BARRAGES

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8. GUIDELINES ON EMERGENCY ACTION PLAN (EAP) 8.1 INTRODUCTION The EAP is a useful tool intended to minimize the consequences of a dam failure or malfunction, regarding the population living downstream. In the last 30 years, several countries became aware of the new approach requested by modern society and developed regulations on this matter, creating a dam classification system according to potential downstream hazard and establishing the EAP for dams with a high significant risk Initially the EAP was applied to medium and large dams, and nowadays it is also applied to small dams as a consequence of the great number of such structures and that 87% of the victims related to dam failures have been caused by small dams, according to the experience in the United States - Bureau of Reclamation, along the period from 1970 to 1997. It is interesting to point out from this experience, that 99% of the victims were situated along the 24 km downstream of the dams. The Emergency Action Plan typically falls under the preventive measures to be taken regarding dams safety. For many years these aspects have been taken into account in different regulations and more demanding safety criteria has been established for those dams in which failure or malfunction, even with a very low probability, may cause severe consequences to the downstream population. The purpose of this document is to provide findings, recommendations and strategies to significantly increase the application of Emergency Action Plans to high hazard small dams. The recommendations and strategies can be implemented by policymakers, state and local dam safety officials and dam owners, with the collaboration of the state and local emergency agencies. An EAP is essential for small dam owners and first responders in the event of a dam failure resulting from a natural event (such as a big storm or earthquake), from an accident or from a manmade event. 8.2 HOW TO DEVELOP AN EMERGENCY ACTION PLAN The process of developing an EAP for a small dam generally follows the next steps, as pointed out by Abadjiev [2]: Determine the potential inundated area downstream in case of a dam failure. Two scenarios are to be considered: inundation at maximum probable flood through the spillway without dam failure, and inundation with dam failure. Different failures according to their reasons and development are to be considered as overtopping, piping, etc. Prepare inundation maps clearly indicating the flooded areas and the time at which the wave will reach the downstream settlement or important area. Determine and identify the situations and events that could initiate an emergency action and specify the corresponding actions to be taken and by whom. Develop clear instructions to explain how the operation staff must react before and during emergency. Identify all entities, jurisdictions, agencies and individuals, who will be involved in the emergency actions. Coordinate the development of the EAP with all parties. This interaction should include the discussion of an emergency operation center and discussion of the evacuation with destinations, priorities and procedures, post-flood actions (recovery and cleanup) and all other measures. These discussions must be concise and productive, and 140
present visual information. It must be underlined that the development of an EAP does not mean that the dam is not safe. It is advisable that all parties and the public are invited to participate in a visual inspection of the dam because they can bring practical suggestions that could be taken into account. All parties, including the public, must feel involved in the EAP. Identify all primary and auxiliary communication systems for continuously internal and external communication. List and prioritize all persons and entities involved in the notification process and create the notification flowchart. Develop a draft of the EAP. The list of the tasks must be complete (nothing should be omitted) and easy to understand so that it can be readily followed. Determine the responsibilities under the plan: - owner responsibility - responsibility for notification - responsibility for evacuation - EAP coordinator responsibility The EAP should foresee actions prior to and following the development of emergency conditions. These actions include: - surveillance - access to the site - response during periods of darkness - response during periods of adverse weather - emergency supplies, resources and transport means - alternative means of communication - coordinating information on flows Review and discuss the EAP draft with all parties included in the notification list. The EAP must be clearly understood by everyone. The public (community) should also be invited to participate in the EAP revision meeting because their involvement helps in the elaboration of a better EAP and also gives support to the emergency actions. In the following paragraphs the main points of the establishment of an EAP are analyzed. 8.3 EVALUATION OF POSSIBLE RISKS In the event of a dam failure, the potential energy of the water stored behind even a small dam is capable of causing loss of life, serious property damage and an extended period of absence of the services that dams provide. The EAP should be applied to all small dams with a high hazard potential, which is directly correlated to the population, properties and the environment downstream. It is important to analyze and evaluate the possible dam hazards, in order to perform a more rational approach to the EAP establishment. 8.3.1 Overtopping During Extremes Floods Considering that about 90% of all small dams are embankment dams, and that 2/3 of those dams have failed as a consequence of extreme floods, it is very important to perform a thorough revision of the spillway or outlet structures, in order to evaluate its maximum discharge and compare it with the maximum flood calculated based on more up to data values from the dam site and the basin contribution area. 141
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SMALL DAMS Design, Surveillance and
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FOREWORD The ICOLD - International
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ACKNOWLEDGEMENT The Ad Hoc Committe
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FOREWORD ACKNOWLEDGEMENT SUMMARY TA
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5.5.5 Compaction in confined areas
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7.2.1 Introduction 7.2.2 Spillway c
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1. SMALL DAMS DEFINITION AND CLASSI
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2 Fig. 1.2 - Relationship H . V wit
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1.3 REFERENCES [1] French Committe
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2.3 ZONED EARTHFILL DAMS In arid pa
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sloping core guarantees water impou
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Fig. 2.11 - Hlinky Concrete Gravity
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Fig. 2.13 - Photograph of Neusberg
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The gabion dam as the gabion retain
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Some inflatable dams are operated b
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3.1 INTRODUCTION 3. SAFETY OF SMALL
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Condition Effect on safety 13. Dama
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Fig. 3.2 - Massive dam break overto
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and suffusion or internal instabili
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downstream part of the embankment m
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small dam impounding a lot of water
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Whenever the Supervising Authority
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emergency management organizations
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c) The decommissioning plan should
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5.1 INTRODUCTION 5. FEATURES OF THE
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5.2 DESIGN FLOODS Inadequate flood
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downstream slope will show seepage
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Fig. 5.2 - Design Freeboard 5.4.3 F
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2 U f Fe S 1400 D Where Uf is the d
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Maximum compaction is obtained at c
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characteristic must be determined.
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5.6.1 Foundation Watertightness The
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� A continuous vertical chimney d
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Thickness of pervious layer Thick D
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t 5.7.1.4 Practical Considerations
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It is generally accepted that cohes
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� Simple Bishop (1955) � Spence
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� The elements for surface draina
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The supporting layer for the rip-ra
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For very small reservoirs (fetch of
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The junction of the downstream slop
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Fig. 5.14 - Hongshiyan homogenous d
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material has been left in place or
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The homogeneous dam is recommended
Page 89 and 90: [3] OL and OH soils are not recomme
Page 91 and 92: part (core) lies in the zone (Fig.
Page 93 and 94: 6. GUIDELINES ON SURVEILLANCE OF SM
Page 95 and 96: cases the owner may retain the serv
Page 97 and 98: Surface displacement on an embankme
Page 99 and 100: Fig. 6.1 - Leakage measurement usin
Page 101 and 102: Water Level Sounder - Details of th
Page 103 and 104: pressure) Left abutment 2 5 Weir ga
Page 105 and 106: Fig. 6.9 - Recommended standpipe pi
Page 107 and 108: the others weir gauges need to be i
Page 109 and 110: � Earthquakes sensible at the dam
Page 111 and 112: APPENDIX INSPECTION CHECKLIST FOR S
Page 113 and 114: Exposed reinforcement � The condu
Page 115 and 116: These spillways can be lined or unl
Page 117 and 118: flowing water. Flowing water with h
Page 119 and 120: Fig. 7.3 - Installation of the arti
Page 121 and 122: Fig. 7.7 - Dam overtopping protecti
Page 123 and 124: complete construction was in 2001,
Page 125 and 126: In some cases, the downstream face
Page 127 and 128: Tube-a-manchettes injection system
Page 129 and 130: 7.3.5 Slope Protection Measures 7.3
Page 131 and 132: Pipe Rehabilitation SLIPLINING MODI
Page 133 and 134: Conditions Pros Cons Comments types
Page 135 and 136: Embankment dams that have properly
Page 137 and 138: and minimize erosion. Design of sui
Page 139: [20] SMEC- “Draft Guidelines for
Page 143 and 144: Fig. 8.1 - Three small dams in casc
Page 145 and 146: Social Disruption low (rural area)
Page 147 and 148: Fig. 8.4 - Flood water level after
Page 149: 8.9 REFERENCES [1] BURREC (1994) -
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