D. C. White 3 ’ *, M. Williams 3 , S. L. Barr 3 
School of Civil Engineering & Geosciences, Newcastle University, UK - davina_cherie@yahoo.com 
KEY WORDS: Hyperspectral, Vegetation, Soil, Radiometry, Spectral, Environment, Analysis, Detection 
ABSTRACT: 
Previous studies conducted under controlled laboratory and controlled field conditions have demonstrated the ability of 
hyperspectral techniques to detect vegetation stress associated with elevated levels of soil gas and associated soil oxygen depletion. 
This paper investigates the capability and transferability of these hyperspectral techniques, in particular the Smith et al. (2004) 
725:702 nm ratio, to identify vegetation stress features associated with sub-soil disturbance resulting from gas pipeline earthworks 
under heterogeneous field conditions. Field spectroradiometry data of barley were acquired in 2005 and 2006 at selected transects 
perpendicular to a stretch of buried gas pipeline in Aberdeenshire. Spectral reflectance and absorption features in the VIS-NIR are 
evaluated through first derivate analysis to establish their position, shape and magnitude and used to determine narrow waveband 
ratios which are tightly coupled to changes in photosynthetic function resulting from vegetation stress. First derivative ratios, 
723:700 and 725:702 nm, detected vegetation stress above the gas pipeline where soil had been disturbed and were the same order of 
magnitude for the 2005 and 2006 data. Ratio values were similar to those conducted under controlled conditions by Smith et al. 
(2004), with differences of up to 56 % for spring barley between locations of soil disturbance and locations away from the pipeline, 
R 2 accounting for up to 62 % of the variance in the ratios of the regression. Student’s T-tests revealed that the ratios were 
statistically significantly different between stress and no known stress within zones of soil disturbance at the 0.05 confidence level. 
1. INTRODUCTION 
Remediation involves the reinstatement of the land, flora, and 
other land use, where the sub-surface soil has been disturbed, as 
close as possible to its original condition. Sub-surface soil 
disturbance associated with gas pipeline earthworks can have an 
impact on adjacent land potentially resulting in drainage 
misalignment and collapse, sub-soil compaction (Pers. Comm. 
Donal Cullen, Bruce Mackie and Gerald Banks), and mixing of 
surface and subsurface horizons. These impacts can lead to 
changes in organic matter, clay, pH, aeration, water retention 
and nutrition (De Jong and Button, 1973; Rimmer, 1991). 
Vegetation stress associated with sub-surface soil disturbance 
has been observed as visual symptoms of chlorosis, stunted 
growth and sparse vegetation cover. To date research evaluating 
the health of vegetation overlying gas pipelines has been 
confined primarily to controlled laboratory and controlled field 
test sites, such as Smith et al. (2004), Noomen et al. (2006), and 
van der Meijde et al. (2006). These studies have demonstrated 
the capability of hyperspectral techniques (first derivative 
analysis, band ratios and continuum removal) to detect 
vegetation stress intimated to be a generic response to soil 
oxygen depletion resulting from elevated levels of soil gas. 
Smith et al. (2004) also suggested that their first derivative 
725:702 nm ratio could be employed to detect other forms of 
soil oxygen depletion, such as sub-soil compaction and 
waterlogging, which can result from pipeline earthworks. 
Hyperspectral remote sensing has the potential to provide a 
solution for detection and monitoring of pipeline earthworks 
associated sub-surface soil disturbance which can be inferred 
from resultant surface vegetation stress features. A key 
capability of hyperspectral data are their near contiguous 
narrow spectral wavebands which lend to first derivative 
analysis providing a more robust approach (much less affected 
by extraneous variables, such as partial plant cover under stress 
conditions) than broad band vegetation indices such as NDVI. 
Hyperspectral remote sensing is also potentially capable of 
providing more rigorous, reliable and repeatable detection and 
monitoring than current visual inspections from aircraft 
overflights. Visual inspections can be unreliable at identifying 
stress due to human subjectivity, and are personnel and time 
intensive (Hausamann et al., 2003; Zimig et al., 2002). 
The aim of this paper is to determine the capability of 
hyperspectral field spectroradiometry data to identify surface 
vegetation stress features associated with sub-surface soil 
disturbance resulting from gas pipeline earthworks under 
heterogeneous field conditions. Spectral reflectance and 
absorption features in the VIS-NIR are evaluated through first 
derivate analysis to establish their position, shape and 
magnitude. These first derivative VIS-NIR features are used to 
identify which narrow waveband ratios are tightly coupled to 
changes in photosynthetic function resulting from vegetation 
stress, in particular the Smith et al. (2004) ratio. 
2. FIELD METHODS AND DATA ANALYSIS 
2.1 Study site 
The study area consists of a 9 km stretch of 508 mm buried 
Natural Gas Liquids (NGL) pipeline in Aberdeenshire, Scotland, 
installed and remediated in 1983. A second 457 mm gas 
pipeline is also present within the same corridor and was 
installed in 1980 (Figure 1). Land use is predominantly arable 
crops (barley, wheat and oats) with some grassland. The 
Corresponding author.