The stability of upstream deposited tailings dams is dependent on maintaining a drawn down phreatic surface and unsaturated profile in its outer edge. However, it has been speculated that intense rainfall events could induce unexpected translation of pore air and water pressures into the tailings profile and thus compromise the effective stress in the unsaturated zone or result in a sudden rise in the phreatic surface. This phenomenon, known as the Lisse effect, has been observed and studied in hydrological sciences to explain the rapid delivery of antecedent hillslope groundwater during storm events. However, the phenomenon has not been comprehensively applied to evaluating tailings dam slope stability. In this paper, the outcomes of controlled observations of the phenomenon in column and analytical experiments, are assembled and evaluated in terms of the surface water application volumes and rate, the properties of the porous media and the resultant nature of pore pressure and phreatic surface responses. In addition, application of applied theories to evaluate the rapid transmission of pore pressures through a profile in response to an advancing wetting front, leads to the development of a methodology that could be applied to tailings materials of a range of hydraulic conductivities and water retention characteristics. The theory is applied to a series of profiles of different tailings porous media, using varied water application rates. Resultant perturbations in phreatic surface elevation and changes to pore pressures in the unsaturated zone are used to evaluate changes in effective stress distribution in the unsaturated outer wedge and subsequent stability criteria. A possible evaluation algorithm for assessing stability criteria is suggested.
MULTIFILE
This paper presents five design prototypes for cool urban water environments developed in the 'Really cooling water bodies in cities' (REALCOOL) project. The REALCOOL prototypes address an urgent need: urban water bodies, such as ponds or canals, are often assumed to cool down their surroundings during days with heat stress, whereas recent research shows that this is not always the case and that urban water bodies may actually have warming effects too. There are, however, indications that shading, vaporising water, and proper ventilation can keep water bodies and their surroundings cooler. Yet, it is necessary to explore how these strategies can be optimally combined and how the resulting design guidelines can be communicated to design professionals. The REALCOOL prototypes communicate the spatial layout and biometeorological effects of such combinations and assist design decisions dealing with urban water environments. The micrometeorological simulations with Envimet showed that the prototypes led to local reductions on daytime PET from 1 °C to 7 °C, upon introducing shade. Water mist and fountains were also cooling solutions. The important role of ventilation was confirmed. The paper discusses and concludes about the use of the prototypes as tools for urban design practice.
Urbanisation and climate change have an effect on the water balance in our cities resulting in challenges as flooding, droughts and heatstress. Implementation of Sustainable Urban Drainage Systems (SuDS) can help to restore the water balance in cities by storing and infiltrating stormwater into the subsurface to minimise flooding, restoration of groundwater tables to prevent droughts, lowering temperatures by evapotranspiration to fight heatstress. Urban planners and otherstakeholders in municipalities and water authorities struggle with implementing SuDS at locations where infiltration of water seems challenging. Questions arise as: can you infiltrate in countries as The Netherlands with parts under sea level, high groundwater table and low permeable soil? Can you infiltrate in Norway with low permeable or impermeable bedrock and frozen ground most of theyear? How do you find space to implement SuDS in the dense urban areas of Bucharest? These questions are answered by researchers of the JPI Water funded project INovations for eXtreme Climatic Events (INXCES).To answer the question on ‘can we infiltrate stormwater under worse case conditions?’, testing of the hydraulic capacity take place at rainwater gardens in Norway (Bergen and Trondheim) and (bio)swales in the low lying parts of The Netherlands. The first results show that even under these ‘extreme’ hydraulic circumstances the hydraulic capacity (or empty time) is sufficient to infiltratemost of the stormwater throughout the year.INXCES exchanged researchers on an international level, shared research results with stakeholders and sets up guidelines for design, implementation and maintenance of SuDS to promote the implementation of sustainable water management systems throughout the world.One of the tools used to promote SuDS is www.climatescan.nl, an open source online map application that provides an easy-to-access database of international project information in the field of urban resilience and climate adaptation. The tool is able to map several sustainable urban drainage systems as has been done for Norway, The Netherlands, Romania and other countries in the world.The tool is used for engagement with stakeholders within EU projects as INXCES and WaterCoG and resulted in international knowledge exchange on infiltration of stormwater under extreme climate and geohydrolic circumstances.
Climate change is increasing the challenges for water management worldwide. Extreme weather conditions, such as droughts and heavy rainfall, are increasingly limiting the availability of water, especially for agriculture. Nature-Based Solutions (NBS) offer potential solutions. They help to collect and infiltrate rainwater and thus play an important role in climate adaptation.Green infrastructure, such as rain gardens (sunken plant beds) and wadis (sunken grass fields for temporary storage of rainwater), help to restore the urban water balance. They reduce rainwater runoff, stabilize groundwater levels and solve problems with soil moisture and temperature. Despite these advantages, there is still much ignorance in practice about the possibilities of NBS. To remedy this, freely accessible knowledge modules are being developed that can help governments and future employees to better understand the application of these solutions. This research, called GINA (Green Infrastructure in Urban Areas), aims to create more sustainable and climate-resilient cities by developing and sharing knowledge about NBS, and supports local governments and students in effectively deploying these green infrastructures.
