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Displaying One Session

Session Type
Academic Sessions
Date
02/24/2022
Session Time
09:30 AM - 10:40 AM
Room

Hall B

EFFECTIVENESS OF GREEN URBAN SURFACES TO MITIGATE EXCESS HEAT DURING HEATWAVES.

Session Type
Academic Sessions
Date
02/24/2022
Session Time
09:30 AM - 10:40 AM
Room

Hall B

Lecture Time
09:30 AM - 09:40 AM

Abstract

Abstract Body

Heatwaves create the second-largest number of deaths from Australian natural disasters. Human thermal comfort is a priority in heatwaves along with the undue burden on energy demand. The heatwave impacts for cities could be intense due to energy budget changes with the urbanization process and Urban Heat Island (UHI) effect. This paper investigates the effectiveness of green surfaces during heatwave events by arguing the city will perform better with more greener for excess heat.

The study was conducted in the City of Melbourne during the well-documented four heatwave events in 2009 (28-30 Jan), 2014 (14-16 Jan) and 2019 (2 events; 6-8 Dec and 28-30 Jan). The Air Pollution Model (TAPM), coupled with UCLEM urban canopy scheme was used to simulate heatwave events with 1 Km resolution. The existing urban surfaces were modified with green surfaces such as urban trees and green roofs. Urban tree ratio was changed in the Central Business District (CBD) as 0%, existing (15%) and 5% increase (20%) in the scenarios of T1, T2 (baseline for the whole study-BSL) and T3, respectively. Green roofs were performed as 50%, 70% and 90% as G1, G2 and G3 (0% in BSL). Both surface parameters were combined in C1 (5% increased canyon trees with 50% green roofs), C2 (5% increased canyon trees with 70% green roofs), and C3 (5% increased canyon trees with 90% green roofs).

From the compared results with BSL (T2), C3 performed the best maximum and minimum temperature (Tmax and Tmin) reduction for all heatwaves (except Tmax in 2014 – G3 performed effectively). For 3-day averaged temperatures (heatwaves exist for 3 or more days), the temperature reduction from C3 was ranged from 1.2 to 2.8°C for Tmin, while Tmax rangedfrom 0.4 to 0.8°C. Therefore, we emphasis green surfaces in cities as potential mitigation strategies to drop the day and night-time temperatures in heatwave events. However, only urban trees distributed in canyons and urban parks cannot cool the temperatures effectively, and we propose combined strategies for the best cooling effectiveness.

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QUANTIFICATION OF URBAN COOLING BY VEGETATION - A MODELLING APPROACH

Session Type
Academic Sessions
Date
02/24/2022
Session Time
09:30 AM - 10:40 AM
Room

Hall B

Lecture Time
09:40 AM - 09:50 AM

Abstract

Abstract Body

There is broad agreement that urban vegetation can play a major role in mitigation of the urban heat island (UHI) effect. However, the lack of precise methods to quantify required amount of vegetation and its cooling efficiency remains a major barrier for its effective application. In this study a calculation model is proposed that can be used to quantify the cooling effect of urban vegetation based on the First Law of Thermodynamics. The obtained Energy Transfer Profile (ETP) shows values for produced amounts of convective- (QH), radiative- (QR) and latent (QE) heat by present materials through conversion of absorbed incoming solar radiative energy. Obtained ETPs from a specific Amsterdam street exposed to an average direct solar radiation of 8042 W/m2day during a typical heat wave day show that the surface temperature of present vegetation does not increase to above 38°C. This is because urban vegetation converts almost all of the absorbed solar energy into latent heat what results in a local air temperature of 8°C lower in comparison to situations where vegetation is absent. In contrast, the ETPs of typical abiotic urban building materials show that under similar climatological conditions masonry heats up to 61°C and concrete to 60°C. Validation of the model by measurements showed a high significance of the findings. The proposed calculation model is an effective tool for the quantification of the energy balance and vegetative cooling of urban sites

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TOWARDS CLIMATE RESILIENT CITIES: QUANTIFYING ENVIRONMENTAL IMPACTS FROM URBAN TRANSFORMATIONS USING SUPPLEMENTARY IOT SENSOR NETWORKS

Session Type
Academic Sessions
Date
02/24/2022
Session Time
09:30 AM - 10:40 AM
Room

Hall B

Lecture Time
09:50 AM - 10:00 AM

Abstract

Abstract Body

The LIFE CRITICAL project (lifecritical.eu) aims at harnessing existing urban environments against future impacts from climate change. Through an innovative approach in Dordrecht (NL) and Bradford (UK), combining state-of-the-art Internet of Things (IoT) sensor technologies and participatory citizen tracks, we aim at (1) quantifying environmental impacts from climate-resilient urban transformations and (2) informing citizens on environmental impacts from public space modifications. This work describes the sensor selection, experimental setup, calibration and first-year findings of a dedicated highly-granular environmental sensing network in Dordrecht (NL). This supplementary sensor network deployed at 15 locations within a 800m² residential area in Dordrecht (Wielwijk) includes microclimate (temperature and relative humidity) and air quality (nitrogen dioxide; NO2) sensors to monitor environmental impacts before, during and after an urban design transformation. This transformation includes the redesignation of a busy roadway towards new green and blue infrastructure (Tromptuinen), and redesign of the existing Wielwijk park. First-year results demonstrate the cooling capacity of urban green spaces with observed temperature differences between park and roadside locations of up to ~4°C during heat waves, while air quality in the Wielwijk area is clearly impacted by the nearby A16 highway with average NO2 concentrations ranging from 22.23 µg/m³ to 36.24 µg/m³ at the considered locations. Steeper pollution gradients (more rapid declines) are observed in green areas, when compared to residential areas, as visualized by the NO2 gradient between the A16 and the Wielwijk park. This long-term (2019-2025) environmental sensing network builds evidence on the local impacts from nature-based solutions. Moreover, validation of the considered IoT (sensor and calibration) approach is foreseen by co-locating 3 sensor units next to a reference station to providing real-time information on the expected field performance of the sensor network.

Acknowledgements

The CRITICAL project is funded by the EU LIFE programme (LIFE18 CCA/NL/001123).

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WATERSPACE: A SPATIAL MODEL OF THE URBAN WATER CYCLE

Session Type
Academic Sessions
Date
02/24/2022
Session Time
09:30 AM - 10:40 AM
Room

Hall B

Lecture Time
10:00 AM - 10:10 AM

Abstract

Abstract Body

This research seeks to improve the theoretical foundations of sustainable urban design in relation to water. A systematic framework to organise water-related urban design research and practice could help develop effective ways to reduce the impacts of urbanisation on the water cycle. However, existing methods, such as 'water-sensitive urban design' conceptualisations and neighbourhood sustainability assessment tools, emphasise urban design practice, lacking a complete evidence-based model of the water cycle in cities.

The research objective of this study was therefore to construct a novel spatial model of the water cycle in cities. This task required synthesising and organising scientific evidence from the environmental sciences. A system dynamics methodology aided by a Driver-Pressure-State-Impact-Response (DPSIR) framework was applied to the comparative analysis of the natural water cycle and its altered version in cities. An undisturbed cool forested landscape was used as reference natural landscape as this kind of landscape presents the most complete and desirable version of the natural water cycle to be emulated by cities.

The resulting model brings together those urban spatial features involved in generating water cycle mechanisms and processes. While some of these features can be found scattered within the sustainable urban design literature, many have not been linked to the water cycle until now. Another contribution of the model is its structure including a new hierarchy of four three-dimensional layers of the water cycle proposed: the precipitation layer, the canopy layer, the surface layer, and the groundwater layer. These layers organise the variety of processes of the water cycle and help assign causal relationships between them and urban form elements within each layer. The model also points at analogies between structural elements in forests and cities. From these analogies criteria and indicators for urban landscapes to mimic the reference landscape can be deduced.

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Q&A

Session Type
Academic Sessions
Date
02/24/2022
Session Time
09:30 AM - 10:40 AM
Room

Hall B

Lecture Time
10:10 AM - 10:40 AM