Keywords

1 Main Objective

The main objective of the WG is to investigate the accidents happening and to develop recommendations for mitigating the effects of accidents. This task has been undertaken by an international group of structural and mechanical professionals, specialized in hydraulic structures such as navigation locks, weirs in navigable rivers and canals, shipyard docks, flood and tide barriers. The group started its proceedings in November 2021. It aims to collect, assess and systemize the existing know-how on handling accidents and calamities in hydraulic structures, including failure mechanisms, their assessments, and the rules of effective handling. The causes of accidents, such as unforeseen conditions, lack of maintenance, improper operation and navigation errors will be evaluated. The investigation will be focused on the engineering aspects but in correlation with the multi-task and multi-disciplinary actions to be taken after the accident has actually happened. The WG is aware that handling accidents and calamities is an interdisciplinary matter involving the actions like:

  • Stabilizing the situation, limiting the damage;

  • Rescuing endangered people and property;

  • First reassessment of preventive measures;

  • Preventing failures of related structures;

  • Informing the stakeholders (like services involved, local residents, navigation);

  • Restoring control of water flow;

  • Documenting relevant events, collecting data and evidence;

  • Investigation, choice of repair strategy;

  • Temporary measures prior to actual repair;

  • Planning and contracting of the repair;

  • Performing the repair, commissioning, resuming normal operation;

  • Implementing lessons learned.

Most of these actions can substantially be optimized when the root causes of accidents are properly investigated, identified and communicated. These root causes are often related to engineering and operation, which explains the focus of the WG. An example is the accident at the Rhône River Sablons Lock in France on February 18, 2020 (Fig. 1), which was caused by a number of technical issues with the downstream gate. As a result, 2 central gate elements collapsed under the pressure of 8 m of differential water head. A barge carrying 2200 tons of toxic, highly inflammable Vinyl Chloride Monomer (VCM) was flushed downstream and severely damaged. This accident, further discussed in the WG Case Study by Masson (2022), resulted in a number of local evacuations and a navigation interruption of one and a half months.

Fig. 1.
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Barge the Pampero after accident at the Sablons Lock, France, photo by Vivre Ici Vallée du Rhône Environnment

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The Working Group will, occasionally, also address other than technical backgrounds of accidents and calamities. However, the WG does not intend to deliver a comprehensive guideline for the management of accidents and calamities, and particularly not for the issues like the division of responsibilities, mitigating the potential losses, evacuation plans, communication procedures etc. The focus remains on the technology and on the interaction between the crews and the users of navigation sites on the one hand, and the affected structures and systems on the other hand.

2 Classification of Accidents

One of the first steps after the accident happens is the classification of its severity. This classification usually determines the organizational level and the procedures of further handling. The Working Group will investigate the regulations in this matter followed various countries, including those of the WG members, compare the actual field experiences with these regulations, and draw general conclusions, possibly with recommendations based on lessons learned.

The most global differentiation is that between “routine” accidents and calamities. Merriam Webster defines a calamity as “a disastrous event marked by great loss and lasting distress and suffering”. In this view, any accident or failure that endangers life or health should be categorized as a calamity. Any classification – including the differentiation between accident and calamity – may, however, also depend on the perspective. For example, the damage to a lock gate caused by the ship collision shown in photo (a) of Fig. 2 will in the first instance be a calamity for the waterway administration, while the sunken vessel in photo (b) of Fig. 2 will harm more the shipping company, see Daniel and Paulus (2019/2).

Fig. 2.
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a) Ship collision with Kiel Canal lock gate, Germany, photo by F. Behling, Kieler Nachrichten; b) sunken barge in IJmuiden Locks, Netherlands, photo by Rijkswaterstaat

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The Working Group intends to determine objective, well-balanced criteria of accident classification, taking into account the interests as well as damages and losses suffered by all parties involved.

3 The WG-241 Plan of Action

A general plan of the WG investigations was laid out in the “Terms of Reference” (TOR), in accordance with the PIANC standard procedures. This document was discussed and approved by the PIANC Inland Navigation Commission (InCom) in March 2021. It describes the intended final product (report), emphasizing that it should draw clear distinctions between emergencies and regular procedures in face of a calamity. The report should by no means be received by the engineering community as imposing bureaucratic or other limits to the methods of accident handling. It should rather provide awareness of the consequences of different approaches; and recommend good practices.

On its kick-off meeting in November 2021, the Working Group decided that an effective approach to meet these PIANC InCom Terms of Reference will be to first perform a number of case studies of real-life accidents and calamities, and the manners in which they had been handled. The factual material collected in this way will allow for comparisons, assessments of effectiveness of various actions, and – finally – conclusions and recommendations of good practices. At the time of writing this paper, a number of case studies have already been performed. In addition, various accident investigation reports by other parties have been collected.

Simultaneously, the WG identified and reviewed the existing publications in the field of accident handling, including those of PIANC. Although accidents and calamities in hydraulic structures have not, so far, been covered by PIANC in a single comprehensive report, some specific aspects of this subject were discussed as part of other concerns. The following existing PIANC reports appeared to contain helpful information:

  • WG 112: Mitigation of Tsunami Disasters in Ports;

  • WG 119: Inventory of inspection and underwater repair techniques of navigation structures (concrete, masonry, and timber) both underwater and in the dry;

  • WG 137: Navigation Structures – their Role within Flood Defense Systems;

  • WG 151: Design of Lock Gates for Ship Collision;

  • WG 155: Ship Behavior in Locks and Approaches;

  • WG 175: A Practical Guide to Environmental Risk Management for Navigation Infrastructure Projects;

  • WG 192: Developments in the Automation and Remote Operation of Locks and Bridges;

  • TG 193: Resilience of the Maritime and Inland Waterborne Transport Systems.

  • In addition, the following still active PIANC Working Groups might potentially be of interest:

  • WG 182: Underwater acoustic imaging of waterborne transport infrastructure;

  • WG 199: Health monitoring for port and waterway structures;

  • WG 215: Accidental impact of ships on fixed structures – Update of PIANC WG 19;

  • WG 233: Inspection, maintenance, and repair of waterfront facilities.

All these studies resulted in the intended layout of the Working Group report as globally indicated below. This layout is now a framework for further activities of the Working Group.

  1. 1.

    Summary and Terms of Reference:

    • Introduction, objectives, Terms of Reference;

    • Summary, references to Appendices.

  2. 2.

    Context and classification of accidents:

    • As far as helpful to activate appropriate procedures, no bureaucratization;

    • Simple classification, there is normally no time to loose.

  3. 3.

    Identifying and reducing the risks:

    • Although the subject is handling accidents that actually happen (i.e. not preventing them from happening), the general links to risk assessment are desired;

    • Focus on construction, operation, maintenance, not only the strength of structure.

  4. 4.

    Investigation of accidents:

    • When, by whom, and how deep? Relation with classification of accidents;

    • Knowledgeable, interdisciplinary, impartial, specific, detailed, …

    • Why the design did not prevent the accident from happening?

  5. 5.

    Handling life safety risks:

    • Life safety as an absolute priority;

    • Life safety in design, operation, maintenance, …

  6. 6.

    Recovering from the damage:

    • Differences from ‘routine’ projects;

    • Discuss (further develop?) the “fish diagram” (see drawing in Fig. 5), global command structure: who is managing what and when.

  7. 7.

    Evaluation, recommendations and lessons learned:

    • Focus on the handling of accident, do not repeat the investigation;

    • When, by whom, how deep? Distance from the “issues of the day”.

4 Investigations of Accidents

In principle, all accidents to hydraulic structures should be investigated and evaluated, although the level and depth of investigations may differ from case to case. The prior objective of investigations is to determine the direct causes and the factors that contributed to the accident. Waterway administrations may have specific regulations that determine the level and scope of investigations depending on the severity of the accident or calamity. Table 1 below has been extracted from such regulations by the U.S. Army Corps of Engineers that administrates and develops the U.S. waterways, see USACE (2010).

Table 1. Classification of accidents and their investigations according to USACE regulations
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It can be observed that the scope of required investigations is wider for the accidents causing high losses in terms of costs and injuries to personnel (Class A and B) than for the accidents causing low losses (Class C and D). In particular, for Class A or B the Board of Investigation (BOI) will be launched, which includes experts from universities, research institutes and industry; while for Class C or D a routine, internal investigation will normally be sufficient. In both cases, however, the key instructions to be followed by personnel involved are as listed below, Daniel and Paulus (2019):

  • Start the investigation timely, desirably within 1–2 days after the accident. Delays may result in forgotten details or removed evidence.

  • Investigation needs to be impartial.

  • Only knowledgeable, experienced personnel should be members of the investigation team.

  • Ensure that all reports are timely completed, preferably within 30 days after accident.

  • Determine who or what caused the accident, why it happened, where it happened, and how it could have been prevented.

  • Identify all circumstances regarding the event. Was there high water? What time of day was it? What time of year was it? What was the temperature? Was it raining, storming etc.?

  • Describe details, lessons learned, steps to prevent similar accidents or failures from happening again.

The regulations in other countries represented in the WG are similar, although often integrated in a wider context of handling accidents and calamities. For example in the Netherlands, the so-called 3-level approach has been recommended. It comprises: 1) Prevention, 2) Mitigation, and 3) Actual handling. The details can be found in ref. Rijkswaterstaat (2011).

5 Handling Life Safety Risks

Modern management of waterways and hydraulic structures is largely based on risk analysis. Life safety risks are normally given the most prominent place in this analysis. Yet, the analysis of life safety risks is often limited to those hydraulic structures, which – in the case of failure – result in the inundation of the downstream areas. These are mainly the closures in river dams, flood barriers and storm surge barriers. Like other risks, the life safety risks in such structures are plotted, analyzed and evaluated on fault trees and risk matrices. In the Netherlands, the risk analysis – loss of life risk in particular – was a base for dividing the country into the so-called “embankment circles”, with legally limited probabilities of inundation, ref. Overheid (2008). The Dutch methodology to estimate the loss of life in flood risk management has, for example, been discussed by Jonkman (2007).

However, the existing legislation and risk analysis methods do not usually capture the life safety risks of accidents such as a push-tow getting stuck under a dam gate, crew losing control of the vessel nearby the dam, maintenance crews losing control of their equipment, and the like. In all such cases, life safety risks concern the users or crews of hydraulic sites rather than the population of downstream areas. The challenge for the designers and managers of hydraulic structures is to identify such risks, to minimize them, and to provide appropriate actions when the accidents happen.

An example is the tragic accident at the Ohio River Montgomery Dam in January 2005 (Fig. 3) that cost the lives of four crewmembers of towboat Elisabeth M, as discussed by Sullivan (2016) and Daniel and Paulus (2019/1). Although the main cause was the extraordinary flow conditions, the incorrect assessments in field and the resulting human errors contributed to this accident as well. This can be seen from the description in image (a) of Fig. 3, while image (b) shows the sunken towboat. The tragedy resulted in technical measures and restrictions for the navigation through the lock.

Fig. 3.
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Accident at Ohio River Montgomery Dam: a) subsequent stages, Daniel & Paulus (20219/1); b) sunken towboat, photo by US Coast Guard

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Life safety risks do not only appear in large navigation structures. They may also occur at relatively small, recreational or other hydraulic sites. This should not be underestimated, considering that such sites are usually unmanned or remotely controlled, so there is nobody to undertake a rescue action. The least that should be done is then to discourage improper use of such structures by the public by placing barriers, clear warning signs and the like. Figure 4 presents two examples of such measures in small hydraulic structures in the Netherlands. The Working Group will also address such issues.

Fig. 4.
figure 4

Prohibition signs for swimmers and boaters on small river weirs, photos by authors

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6 Recovering from the Damage

It is expected that the large number of case studies referring to actual accidents will enable the Working Group to distinguish typical stages in handling accidents and calamities. The identification of these stages will, in turn, help the professionals involved to effectively manage all the necessary activities and particularly the recovery from the damage. It is important, however, that such stages are not seen as a management’s tool to limit the scope and depth of the required activities, but rather as a guideline to control the process. Accidents and calamities are, after all, “upset events” that happen and proceed irregularly, which requires a great deal of individual focus rather than standard approach.

The preliminary work has already been done in this matter. An example is the USACE Regulation 385-1-99 quoted earlier in this paper, ref. USACE (2010). The WG will also review relevant regulations and practices by other waterway administrations. An idea for discussion and possible further development is the so-called “fish diagram” (Fig. 5), proposed by Daniel and Paulus (2019/1, 2, 3). It distinguishes 5 typical stages of handling accidents and calamities. It also indicates the different urgencies of these stages, as well as the demand for personnel, material and other resources. The depicted relations are briefly commented below.

Fig. 5.
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Stages and engagement of resources when handling accidents

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  • The urgency to act is usually the highest immediately after (if possible even during) the accident. The emerging situation is then out of control. The priority is to regain that control and to prevent or at least limit any further damage.

  • Despite the high urgency, the available means (personnel, material, equipment) to meet the emerging needs are then the lowest. Organizations may exercise freeing these resources at short notice, but it always takes time to effectively mobilize them.

  • Once the control has been restored, one can inventory the damage, investigate its causes and plan the repair. The urgency decreases at this stage but is still high. The engaged resources are already substantial but the main work still needs to be done. It should begin quickly and efficiently.

  • The repair can be done either by the in-house forces or by contractors or by a joined effort of both. USACE largely relies on the in-house forces. The administrations that have outsourced such forces (like Rijkswaterstaat) will need to contract all works. In both cases, the result should be a repaired or replaced hydraulic structure that can safely operate for many years to come.

  • Upon delivery and installation of the repaired or replaced structure, the system will undergo a series of tests. Then it will be commissioned and handed over to the operation and maintenance crews. At this point, the work begins to resemble a regular project, although the urgencies are usually higher.

  • The last stage is the so-called after-care phase when various “teething problems” may occur. They are solved in accordance with concluded agreements. This is also the time to evaluate the accident and to draw lessons learned. The evaluating team should include all main actors, but keep distance from the daily issues. This is marked by a split in the fish’s tail in Fig. 5.

7 Example Case Studies

As already mentioned, the Working Group largely relies on real-life case studies while investigating the accidents in hydraulic structures and drawing appropriate conclusions. By means of examples, two of these case studies are presented below in more detail:

  1. 1.

    Ohio River Markland Lock gate failure in Sept., 2009, Paulus (2022);

  2. 2.

    Meuse River Grave Weir gate damage in Dec. 29, 2016, Daniel (2022).

7.1 The Markland Lock Gate Failure

The Markland Lock and Dam on the Ohio River is located near Warsaw, Kentucky, United States. The accident in question took place on September 27, 2009, and concerned the lower miter gate of the main lock chamber with the clear dimensions of 33.5 m by 365.7 m. The lock has also a parallel auxiliary chamber of the same width but a twice shorter length. Under normal conditions, both chambers and the dam carry the water level difference of 10.6 m.

The main reason of the lower gate failure was the uncontrolled filling of the lock chamber while the gate was improperly mitered. The flow entered the chamber too soon through the filling valves, overpowered the gate hydraulic drives and slammed the gate two leaves together in an incorrectly mitered position. In that condition, the gate was not capable of carrying the growing differential water head; and was forced by it over the sill. The strut arms broke away and the gate hinge anchors failed. One leaf broke entirely off and fell into water (Fig. 6a), while the other leaf remained upright far away from its operating position (Fig. 6b).

The accident caused a severe damage to both gate leaves, their drive struts, anchors and supporting structures. A cruise ship that was supposed to be locked upbound, broke off her moorings but did not suffer further damage. The navigation shut-down as result of necessary repairs lasted over 5 months.

Fig. 6.
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Markland Lock gate failure: a) anchors of sunken leaf; b) upright leaf forced off its position, photos by USACE

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As the property loss due to the Markland Lock gate failure was over $9 million, the Board of Investigation (BOI) was called upon to investigate the accident, see Table 1 above. The BOI investigation report exposed additional circumstances and shortcomings that contributed to the lock gate failure. All these factors have been collected in the case study and will be analyzed by the Working Group. It is expected that this case will generate a number of lessons learned to be provided in the WG final report.

7.2 The Grave Weir Gate Damage

The Meuse River Grave weir damage of December 2016 was caused by a ship collision. This weir is of a so-called “bridge-weir” type, of which only two exist in the world. Hydraulic loads are carried by liftable water retaining panels, supported by vertical beams (posts) that, in turn, are hinged to bridge spans above the weir bays. During floods, the beams are hoisted out of water to the horizontal position under the bridge decks, in order to facilitate high water discharge. The Grave Weir has two such bridge spans. Under normal conditions, it controls a water level difference of 3 m.

On December 29, 2016, a downbound tanker Maria Valentine, carrying 2000 tons of benzene, rammed into the northern span at full speed. This happened early in the morning in a dense fog. The ship damaged several vertical beams and panels. Then she dove and passed the weir under the beams. It was considered a wonder that this did not cause any injuries or fatalities on board. Despite the damage on deck, the crew managed to anchor the vessel downstream of the weir. No benzene leaked into the river. Nevertheless, the weir structures were severely damaged (Fig. 7). This in combination with the late closing of the locks in the lateral canal caused the loss of navigation and substantial other damage in a wide area. The tanker itself suffered large damage to the appliances and equipment on deck, but no significant structural damage.

Fig. 7.
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Damage to Grave Weir after ship collision, photo by Rijkswaterstaat

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Due to the large scale of damage, and the risks involved (e.g. in case that the benzene on board caught fire), the final stage of investigations was carried out by the Dutch Safety Board, which is an independent, highest level institution entitled to carry such investigations. The Dutch Safety Board decides by itself which incidents it will investigate and may do so when asked or on its own initiative. The Board decided to carry an investigation in January 2017, and the final report was released in May 2018. This report, like the BOI report on the Markland Lock accident, revealed a large number of organizational and other issues that contributed to the calamity and might have potentially caused still more damage. The Working Group will certainly consider the findings of this report in their further studies.

8 Conclusions

Since the Working Group has only recently been established, it is still too soon to derive conclusions from the investigations performed. The first substantial conclusions and recommendations as regards the handling of accidents and calamities can be expected mid 2023. Nevertheless, the discussions during WG meetings so far allow for a few general notes.

One general note is that while accidents and calamities in hydraulic structures are infrequent events, the consequences of these events are usually harmful for many parties. It is, therefore, highly desirable to develop not only the policy of handling these events but also the effective tools, like the structure of command, means of communication, legal framework for emergency actions, ways to mobilize the required expertise, supplies of materials and equipment etc.

Some administrations of, for example, waterways or harbors do already have such tools, but the real-life examples indicate that the handling of accidents or calamities is often far from optimal. It seems important that the organizations in charge of hydraulic structures:

  1. a)

    maintain the readiness to properly act when accidents happen, for example by frequent exercising;

  2. b)

    keep improving this readiness, for example by applying lessons learned from actual accidents.

These first observations will still be subject to further investigations, assessments and specifications by the Working Group. Should anybody from the PIANC community be willing to share their own experience, expertise, good practices or only ideas in this matter with the Working Group, then please feel encouraged to contact any of the co-authors of this paper.