CM
C.E. Mekel
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1
Hidden Danger
Mapping consequences of underground water infrastructure failure to guide asset management
Continuous functioning of sewer systems and water distribution networks is crucial for liveability, public health and economic prosperity in urban areas. Progressive deterioration of these underground water infrastructures leads to an increased probability of failure. Maintenance is needed to ensure a desired level of functioning. For municipalities and drinking water companies as asset owners, the trend is to develop risk-based asset management. A risk-based asset management strategy links the likelihood of failure with the consequences. Hence, knowledge is needed on the condition of the underground water infrastructure and the consequences in case of failure. Within this strategy, a risk assessment should be performed to prioritise the maintenance and renewal of underground water infrastructure. Based on their criticality, resources can be applied appropriately. The more critical a conduit segment, the more important it is to perform maintenance. To contribute to risk-based asset management, this study investigates the consequences of failure in sewer systems and water distribution networks. In this research, a methodology is developed for mapping consequences of underground water infrastructure failure to guide asset management. Including the consequences of underground water infrastructure failure in the risk determination may lead to a different prioritisation of maintenance activities. Three failure mechanisms are considered: structural sewer failure, hydraulic sewer failure and water distribution network failure. Structural sewer failure leads to partial or complete loss of the load-carrying capacity, whereas hydraulic sewer failure occurs when a system does not meet serviceability requirements for system performance. For water distribution networks, it is assumed that hydraulic failure (caused by overpressure) and structural failure occur simultaneously. Hence, no distinction is made between failure mechanisms in water distribution networks. Using a screening method, the consequences of underground water infrastructure failure are mapped. The consequences of failure are expressed as the affected area and the characteristics of the built environment. The affected area consists of the sinkhole area and the flood zone. The characteristics of the built environment are displayed by means of consequence categories. Within this study, five different consequence categories are taken into account, using hydraulic modelling and (open) classified data. The consequence categories are: 1) Damage to buildings 2) Traffic obstruction 3) Impact on human health 4) Costs of conduit reconstruction 5) Drinking water supply outage. A flat, typical Dutch study area in Tuindorp (Utrecht) is used to test the methodology. For these five consequence categories, findings are illustrated and compared with the results of the hydraulic network functioning according to the Graph Theory method (GTM). This GTM determines the effects of failure of individual conduits on the functioning of a system as a whole, based on a simplified network structure using links and nodes. Results of the analyses show a positive relation between the individual consequences in case of hydraulic sewer failure. For example, critical conduits in the category `damage to buildings', are critical for `impact on human health' as well. Besides, there is a positive relation between the consequence categories and the hydraulic network functioning. Conduits with large diameters are stated as critical for both methods, yet dead-end segments are only critical for hydraulic network functioning. Contradictory, individual consequences are uncorrelated for structural sewer failure and water distribution network failure. The consequences are independent and can not be linked. Besides, there is no relation between the hydraulic network functioning and the individual consequences of structural sewer failure and water distribution network failure.
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Continuous functioning of sewer systems and water distribution networks is crucial for liveability, public health and economic prosperity in urban areas. Progressive deterioration of these underground water infrastructures leads to an increased probability of failure. Maintenance is needed to ensure a desired level of functioning. For municipalities and drinking water companies as asset owners, the trend is to develop risk-based asset management. A risk-based asset management strategy links the likelihood of failure with the consequences. Hence, knowledge is needed on the condition of the underground water infrastructure and the consequences in case of failure. Within this strategy, a risk assessment should be performed to prioritise the maintenance and renewal of underground water infrastructure. Based on their criticality, resources can be applied appropriately. The more critical a conduit segment, the more important it is to perform maintenance. To contribute to risk-based asset management, this study investigates the consequences of failure in sewer systems and water distribution networks. In this research, a methodology is developed for mapping consequences of underground water infrastructure failure to guide asset management. Including the consequences of underground water infrastructure failure in the risk determination may lead to a different prioritisation of maintenance activities. Three failure mechanisms are considered: structural sewer failure, hydraulic sewer failure and water distribution network failure. Structural sewer failure leads to partial or complete loss of the load-carrying capacity, whereas hydraulic sewer failure occurs when a system does not meet serviceability requirements for system performance. For water distribution networks, it is assumed that hydraulic failure (caused by overpressure) and structural failure occur simultaneously. Hence, no distinction is made between failure mechanisms in water distribution networks. Using a screening method, the consequences of underground water infrastructure failure are mapped. The consequences of failure are expressed as the affected area and the characteristics of the built environment. The affected area consists of the sinkhole area and the flood zone. The characteristics of the built environment are displayed by means of consequence categories. Within this study, five different consequence categories are taken into account, using hydraulic modelling and (open) classified data. The consequence categories are: 1) Damage to buildings 2) Traffic obstruction 3) Impact on human health 4) Costs of conduit reconstruction 5) Drinking water supply outage. A flat, typical Dutch study area in Tuindorp (Utrecht) is used to test the methodology. For these five consequence categories, findings are illustrated and compared with the results of the hydraulic network functioning according to the Graph Theory method (GTM). This GTM determines the effects of failure of individual conduits on the functioning of a system as a whole, based on a simplified network structure using links and nodes. Results of the analyses show a positive relation between the individual consequences in case of hydraulic sewer failure. For example, critical conduits in the category `damage to buildings', are critical for `impact on human health' as well. Besides, there is a positive relation between the consequence categories and the hydraulic network functioning. Conduits with large diameters are stated as critical for both methods, yet dead-end segments are only critical for hydraulic network functioning. Contradictory, individual consequences are uncorrelated for structural sewer failure and water distribution network failure. The consequences are independent and can not be linked. Besides, there is no relation between the hydraulic network functioning and the individual consequences of structural sewer failure and water distribution network failure.
Student report
(2018)
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Fokke Dijkstra, Luuk Jordans, Maurits Groenewegen, Florentine Steijlen, Charlotte Mekel, Oswaldo Morales Napoles, Julia Gebert, Jan van Overeem
Terminos Lagoon is the biggest and ecologically most important fluvial-lagoon system of the southern Gulf of Mexico. Rivers, sea and meteorology all influence the lagoon, variable over the year, resulting in a complex situation. To protect this area, it is crucial to know how different hydrological processes, hydrodynamic processes and spatial characteristics influence each other in this context. Using a multidisciplinary approach, this research focused on the question: What is the influence of hydrological and hydrodynamic processes on spatial characteristics of Terminos Lagoon, now and in the future? The study has shown that evaporation has a larger part in the water balance during dry season, where during other seasons the water balance is similar to the annual mean. It is found that the western part of Terminos Lagoon shows different characteristics
than the eastern part, as river discharge plays a larger role in the western part of the lagoon. Secchi depth, temperature, dissolved oxygen, sediments and salinity are all different here compared to the eastern part of the lagoon. Salinity and river discharge, as well as air and water temperatures, show to be highly correlated. A tidal watershed divides the lagoon in two approximately equal areas, following the mentioned separation of east and west. Residual currents flow along the boundaries of the lagoon from east to west. A circular
residual current in the lagoon is observed near the Puerto Real inlet in created temperature and Secchi depth maps. Nortes season shows highest salinity and lowest Secchi depths, where dry season shows lowest salinity. Both inlets are expected to sedimentate and sediments outside the lagoon move westward. Climatological influences are uncertain, though likely effects are increased water temperature, salinity, flushing time and a decrease in residual current. Mentioned effects are likely most noticeable in the eastern part of the lagoon.
Further research is necessary to achieve ecological goals in the region. ...
than the eastern part, as river discharge plays a larger role in the western part of the lagoon. Secchi depth, temperature, dissolved oxygen, sediments and salinity are all different here compared to the eastern part of the lagoon. Salinity and river discharge, as well as air and water temperatures, show to be highly correlated. A tidal watershed divides the lagoon in two approximately equal areas, following the mentioned separation of east and west. Residual currents flow along the boundaries of the lagoon from east to west. A circular
residual current in the lagoon is observed near the Puerto Real inlet in created temperature and Secchi depth maps. Nortes season shows highest salinity and lowest Secchi depths, where dry season shows lowest salinity. Both inlets are expected to sedimentate and sediments outside the lagoon move westward. Climatological influences are uncertain, though likely effects are increased water temperature, salinity, flushing time and a decrease in residual current. Mentioned effects are likely most noticeable in the eastern part of the lagoon.
Further research is necessary to achieve ecological goals in the region. ...
Terminos Lagoon is the biggest and ecologically most important fluvial-lagoon system of the southern Gulf of Mexico. Rivers, sea and meteorology all influence the lagoon, variable over the year, resulting in a complex situation. To protect this area, it is crucial to know how different hydrological processes, hydrodynamic processes and spatial characteristics influence each other in this context. Using a multidisciplinary approach, this research focused on the question: What is the influence of hydrological and hydrodynamic processes on spatial characteristics of Terminos Lagoon, now and in the future? The study has shown that evaporation has a larger part in the water balance during dry season, where during other seasons the water balance is similar to the annual mean. It is found that the western part of Terminos Lagoon shows different characteristics
than the eastern part, as river discharge plays a larger role in the western part of the lagoon. Secchi depth, temperature, dissolved oxygen, sediments and salinity are all different here compared to the eastern part of the lagoon. Salinity and river discharge, as well as air and water temperatures, show to be highly correlated. A tidal watershed divides the lagoon in two approximately equal areas, following the mentioned separation of east and west. Residual currents flow along the boundaries of the lagoon from east to west. A circular
residual current in the lagoon is observed near the Puerto Real inlet in created temperature and Secchi depth maps. Nortes season shows highest salinity and lowest Secchi depths, where dry season shows lowest salinity. Both inlets are expected to sedimentate and sediments outside the lagoon move westward. Climatological influences are uncertain, though likely effects are increased water temperature, salinity, flushing time and a decrease in residual current. Mentioned effects are likely most noticeable in the eastern part of the lagoon.
Further research is necessary to achieve ecological goals in the region.
than the eastern part, as river discharge plays a larger role in the western part of the lagoon. Secchi depth, temperature, dissolved oxygen, sediments and salinity are all different here compared to the eastern part of the lagoon. Salinity and river discharge, as well as air and water temperatures, show to be highly correlated. A tidal watershed divides the lagoon in two approximately equal areas, following the mentioned separation of east and west. Residual currents flow along the boundaries of the lagoon from east to west. A circular
residual current in the lagoon is observed near the Puerto Real inlet in created temperature and Secchi depth maps. Nortes season shows highest salinity and lowest Secchi depths, where dry season shows lowest salinity. Both inlets are expected to sedimentate and sediments outside the lagoon move westward. Climatological influences are uncertain, though likely effects are increased water temperature, salinity, flushing time and a decrease in residual current. Mentioned effects are likely most noticeable in the eastern part of the lagoon.
Further research is necessary to achieve ecological goals in the region.