<p>Green Infrastructure (GI) offers multiple and integrated benefits to urban areas, including relieving pressure on ‘grey’ infrastructure systems by locally managing surface runoff within cities to reduce the risk of urban flooding. Although the use of GI has been shown to attenuate flooding, monitored and quantifiable data determining the effectiveness of GI is imperative for supporting widespread adoption of GI within cities and to provide an evidence-base to inform the design and maintenance procedures of such systems and ultimately influence key decision makers .</p><p>The National Green Infrastructure Facility (NGIF) based in Newcastle-upon-Tyne, UK, is a purpose-built, publicly accessible, ‘living laboratory’ and demonstration site established in 2017, funded by the UK Collaboratorium for Research on Infrastructure and Cities. The NGIF explores how a wide range of green features such as trees, shrubs and soils can help reduce flooding in cities and make them more resilient and sustainable to future changes in climate and urban pressures. The facility hosts a number of novel GI features of varying scale, monitored with dense sensor networks to allow the in-situ measurement of key hydrological, climatic and biophysical variables (e.g. precipitation, temperature, soil moisture, water depth, runoff and outflow rates) which are able to provide quantified evidence of the hydrological performance of sustainable drainage systems (SuDS). Such systems generate detailed insights into how SuDS and nature-based solutions can be used to improve surface water management, optimise geo-energy for building heating/cooling and how systems can be used for urban water treatment.</p><p>GI features across the NGIF include an experimental  and fully functional swale, providing protection to the area of Newcastle-upon-Tyne in which the feature is located, 10 lysimeter bioretention cells, a series of rain-garden ‘ensembles’ and a monitored green roof system. All experimental features are subjected to prevalent environmental conditions and act as fully functional GI systems, but conditions can also be augmented and simulated to ensure that the GI features act as semi-controlled experimental systems to determine responses outside of the natural instrumented record. All environmental data is recorded at high temporal (< 5 minutes) and spatial resolution and is publicly accessible in real-time via the NGIF API.</p><p>This presentation provides an overview of the NGIF and discusses the current research activities taking place across the site. Data is presented from each of the GI systems to demonstrate and discuss their performance and responses during natural and simulated events, including extremes, and to assess their effectiveness in responding to localised changes in climate. Future research directions and collaborative opportunities are also highlighted.</p>

Composite barrier systems, which are two-layer systems of materials (fine-grained material overlying coarse-grained material) of contrasting hydraulic properties, can be used to mitigate the effects of climate change in urban areas, including flooding and shrink swell deformation. Here, a series of experiments were carried out to test a range of materials, including 20-30 mm gravel, recycled crushed concrete, topsoil, and topsoil amended with water treatment residual (WTR). The consideration of waste products here aims to improve the sustainability of composite barrier systems for climate adaptation. The results indicate that WTR-amended topsoil is suitable for use as a fine-grained material in composite barrier systems owing to its enhanced water retention properties. However, while crushed concrete can be used in the coarse-grained layer to form a capillary barrier when the system is dry, once breakthrough has occurred, transmission of water through the barrier is quicker than in composite barriers with 20-30 mm gravel. As such, 20-30 mm gravel is recommended for use in the coarse-grained layer. Two large-scale, outdoor lysimeters were set-up using the recommendations derived from the column experiments. The lysimeter experiments were subjected to a series of simulated rainfall events to enable initial interpretations of composite barrier performance.

Vegetation is important for managing shallow geotechnical assets. However, root water uptake-driven changes in slope hydrology and the near-surface (soil water content, matric suction, and hydraulic conductivity) are highly complex. Improved knowledge of these processes is increasingly important as society faces the threat of a greater prevalence of climate-driven extreme rainfall and drought events. Intrinsic factors affect slope stability, including geometry, soil properties, groundwater, and vegetation-driven matric suction. Field evidence shows that engineered slopes are susceptible to hydrometeorological instability mechanisms and pose a potential failure hazard to asset operation and public safety. This study considers the combination of a novel geophysical monitoring system and geotechnical point sensors for use in controlled laboratory conditions to assess the influence of vegetation on soil-water dynamics in the context of geotechnical infrastructure. The geophysical monitoring system, referred to here as PRIME (Proactive Infrastructure Monitoring and Evaluation system), uses electrical resistivity tomography (ERT) technology to non-invasively image changing subsurface moisture-driven processes. The PRIME system and point sensor arrays are being developed for near real-time data acquisition of transient soil moisture conditions in a suite of soil column experiments. Through addressing the challenges associated with designing integrated geophysical-geotechnical laboratory-scale monitoring experiments, this research aims to provide new tools and approaches to further our understanding of vegetation-driven soil moisture movement to better assess slope instability risk.

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<p>Vegetation is an important tool for managing urban surface water and shallow geotechnical assets. However, root water uptake driven changes in slope hydrology (soil water content, matric suction, and hydraulic conductivity) are poorly understood in heterogeneous soils and under extreme climatic conditions. Slope stability is affected by intrinsic factors, including geometry, soil properties, groundwater and vegetation driven matric suction. Field evidence indicates that engineered slopes are susceptible to hydrometeorological slope instability mechanisms and that these pose a potential failure hazard to asset operation and public safety. The UK hosts 15,800 km of railway network and 7100 km of strategic road network, accounting for 49,000 slopes. This is a significant portfolio of slopes that must be managed and maintained at considerable expense.</p><p>To better understand the influence of vegetation on soil water dynamics in geotechnical infrastructure, Electrical Resistivity Tomography (ERT) is being used. ERT is a non-invasive tool for measuring and imaging subsurface soil moisture dynamics volumetrically. ERT can be used to quantitatively establish how the presence of roots influences transient soil moisture content and suction to assess the effectiveness of vegetation in managing slope hydrology and excess surface water issues in the built environment. This research aims to use 4-D ERT to determine the impact of vegetation on the hydrological behaviour of a high plasticity clay derived sub-soil used in the construction of infrastructure slopes in the southern half of the UK. Laboratory-scale experiments are underway at the UK National Green Infrastructure Facility, Newcastle, using a controlled environment chamber. A suite of soil columns is planted with vegetation, False Oat Grass (Arrhenatherum elatius) and Common Bent (Agrostis capillaris) and feature a 3D ERT electrode array and point sensors for measurement of volumetric water content, matric suction, and electrical conductivity throughout the profile. Through frequent imaging of soil-water-plant interactions and correlation with destructive root architecture imaging, this research aims to highlight how these relationships change over time and respond to extreme weather conditions (drought/inundation) to better predict, manage, and mitigate the occurrence of slope failure. Furthermore, the work aims to improve understanding of vegetation-driven soil moisture movement in the near-surface to better assess seasonal and longer-term slope stability to inform asset management strategies.</p>