Hyperspectral Monitoring of Green Roof Vegetation Health State in Sub-Mediterranean Climate: Preliminary Results.

Patrizia Piro,Monica Moroni,Michele Porti,Emanuela Lupo,Simone Veltri

doi:10.3390/s17040662

Abstract

In urban and industrial environments, the constant increase of impermeable surfaces has produced drastic changes in the natural hydrological cycle. Decreasing green areas not only produce negative effects from a hydrological-hydraulic perspective, but also from an energy point of view, modifying the urban microclimate and generating, as shown in the literature, heat islands in our cities. In this context, green infrastructures may represent an environmental compensation action that can be used to re-equilibrate the hydrological and energy balance and reduce the impact of pollutant load on receiving water bodies. To ensure that a green infrastructure will work properly, vegetated areas have to be continuously monitored to verify their health state. This paper presents a ground spectroscopy monitoring survey of a green roof installed at the University of Calabria fulfilled via the acquisition and analysis of hyperspectral data. This study is part of a larger research project financed by European Structural funds aimed at understanding the influence of green roofs on rainwater management and energy consumption for air conditioning in the Mediterranean area. Reflectance values were acquired with a field-portable spectroradiometer that operates in the range of wavelengths 350–2500 nm. The survey was carried out during the time period November 2014–June 2015 and data were acquired weekly. Climatic, thermo-physical, hydrological and hydraulic quantities were acquired as well and related to spectral data. Broadband and narrowband spectral indices, related to chlorophyll content and to chlorophyll–carotenoid ratio, were computed. The two narrowband indices NDVI705 and SIPI turned out to be the most representative indices to detect the plant health status.

Highlights

Green infrastructure refers to a suite of technologies, such as green roofs, permeable pavements, rain gardens, and bioswales
This paper presents a ground spectroscopy sensing monitoring survey of a green roof installed at the University of Calabria fulfilled via the acquisition and analysis of hyperspectral data
It is worth noting that the green peak for Dianthus and Cerastium is at green wavelengths because healthy plants look green; instead, the Carpobrotus signature shows a peak at red wavelengths because when the plant is healthy it looks red

Summary

Introduction

Green infrastructure refers to a suite of technologies, such as green roofs, permeable pavements, rain gardens, and bioswales. Through the combination of technologies and vegetated areas, they absorb and slow down the flow of stormwater from impervious urban surfaces (streets, parking lots, rooftops, and walkways) that dominate an urban watershed [1,2,3]. Other remarkable advantages of green infrastructures are: their ornamental role, reduction of noises and improvement of thermal effects within the building in which they are installed. Green infrastructures contribute to the diminishment of Sensors 2017, 17, 662; doi:10.3390/s17040662 www.mdpi.com/journal/sensors. High temporal resolution monitoring systems are mandatory in order to check the health state of vegetated areas and ensure that a green infrastructure will work properly Sensors 2017, 17, 662 the urban heat island effects, reducing temperatures via evapotraspiration [4] and guaranteeing biodiversity in the urban environment, representing a novel habitat available for plants and animals.

Methods

Results

Conclusion