the impact of soils and changing environment on buried water infrastructure
TRANSCRIPT
The impact of soils and changing environment on buried water infrastructure
Oliver Pritchard Doctoral Researcher, Cranfield University
PhD Supervisors: Dr. Stephen Hallett and Dr. Timothy Farewell 9th September 2014, AGI Asset management (Water) SIG
UK Soil Variability
UK Soils vary in many ways: Texture (sand, silt clay %) Stoniness Organic content Depth to rock Mineralogy Permeability Natural drainage Consolidation etc.
Over 700 types in UK!
Climatic Data
Hor
izon
D
epth
(cm
)
San
d %
Silt
%
Cla
y %
pH Org
anic
Car
bon
(wt%
)
Bul
k D
ensi
ty
(g/c
m3)
Part
icle
D
ensi
ty
(g/c
m3)
Tota
l Po
rosi
ty (
%)
Wat
er
Con
tent
at
5kPa
; (F
ield
Cap
acity)
Brief
D
escr
iption
of
Hor
izon
0 to 25 20 35 45 7.5 3.1 1.15 2.6 55.8 45.1 Dark greyish brown, stoneless clay; calcareous.
25 to 50 12 28 60 7.9 1.3 1.27 2.63 51.7 46.7 Olive brown, slightly mottled, stoneless clay; moderate
medium subangular blocky structure; calcareous.
50 to 75 7 35 58 8 0.6 1.36 2.64 48.5 45.4 Light olive brown, slightly mottled, stoneless clay; strong
medium angular blocky structure; calcareous.
75 to 150 8 34 58 8.3 0.4 1.4 2.64 47 44.5 Grey, slightly mottled, stoneless clay; massive structure;
calcareous.
Field Records
Soil Maps
Soil characterisation
LandIS The Land Information System
Corrosion Potential
Shrink-swell
potential
www.landis.org.uk
Sand-Washout
Lab analysis
Soil corrosivity
• Number of soil processes which contribute to corrosion
• LEACS – Leakage
assessment from corrosivity and shrinkage
• Provides corrosion risk and likelihood of shrink-swell in a GIS format.
LegendNATMAPleacsCORR_FE
1
2
3
3*
4
4*
5
5*
6
Clay shrink/swell
• Parent material substrate type (defines conditions at pipe/foundation depth, 1.0-1.5m)
• Clayey substrates classed on relationship between bulk density and volumetric shrinkage
• Non-clay substrates classed on relative shrinkability
• Six classes of soil shrink/swell combine with six PSMD (potential soil moisture deficit) bands to give nine vulnerability classes
Natural Perils Directory: Clay-related subsidence = soil factors + climate perturbation model
Ext high
Negligible
Potential Soil Moisture Deficit
Soil Shrink Swell
Provides 9 classes of combined vulnerability
Perturba;ons
+
+ -‐
Vegetation Adjusted Soil Moisture Deficit or
Breaks per month (2005-2012) by soil-shrink-swell potential
Low-‐risk soils – Washout/freezing events?
Peaks in high and very-‐high risk soils – evidence of swelling clays?
Clay shrinkage
Infrastructure Transitions Research Consortium Research
• £5 million EPSRC-funded research project incorporating 8 Universities
• Informing the analysis, planning and design of national infrastructure, through the development and demonstration of new decision support tools.
• This doctoral research sits within ITRC’s Work Stream 2: ‘Understanding the future risks to UK infrastructure networks’
• Cranfield undertaking probabilistic mapping of subsidence at case-
study and UK scale and establishing future risk to infrastructure.
www.itrc.org.uk
Are we ready for [climatic] change?
• Current geohazard models use baseline climatic data • Long-life span of water infrastructure requires a long-term strategic view
(Tran et al. 2014)
• Therefore, there is a need for probabilistic models….
• UK Climate Projections (UKCP09) suggest that the UK is likely to experience;
§ Hotter, drier summers § Warmer, wetter winters § Resulting in up to a 20-40% soil moisture loss – promoting shrink/
swell activity in prone soils
How are extremes and future climate change currently assessed in NPD?
• Mean maximum PSMD considered as ‘average conditions’
• Mean varied by addition of standard deviations (SD)
• Return periods include: – Standard year – 1 in 3 – 1 in 6 – 1 in 15 – 1 in 45 – 1 in 150
Monthly and annual summary values and sta;s;cs; Soil moisture deficit, Soil moisture surplus, Rain, Poten;al Evapotranspira;on
Processing UKCP09 data – Soil Moisture Deficit Scenarios
1,000 x 30 years daily data
1,000 x 30 years: monthly and annual values; Soil Moisture Deficit, Soil Moisture Surplus, Rain, Poten;al Evapotranspira;on
Raw data
Output data
Summary data
Soils Data
Mapping and Interpola;on
Risk -‐ Analysis Infrastructure Data
~10,000 5km grid cells within UK – for each cell, per scenario, ~1.2GB of data is produced!
UKCP09 Weather Generator – Accumulated Potential Soil Moisture Deficit (PSMD)
Combining Potential Soil Moisture Deficit (PSMD) and Soils data
Soil SSWELL value
Probabilis;c es;ma;on of clay subsidence risk
Probabilis;c Accumulated PSMD value
High-‐risk soils
Low-‐risk soils
Drier
We`er
Current clay subsidence risk for Lincolnshire
LegendLincs_2050_NPD
<all other values>
Clay Subsidence RiskExtremely Low
Very Low
Low
Medium Low
Medium
Medium High
High
Very High
Extremely High
2050 clay subsidence risk (10th Percentile)
LegendLincs_2050_NPD
<all other values>
Clay Subsidence RiskExtremely Low
Very Low
Low
Medium Low
Medium
Medium High
High
Very High
Extremely High
2050 clay subsidence risk (50th percentile)
LegendLincs_2050_NPD
<all other values>
Clay Subsidence RiskExtremely Low
Very Low
Low
Medium Low
Medium
Medium High
High
Very High
Extremely High
2050 clay subsidence risk (90th Percentile)
The story so far: high subsidence risk and more leaks to come….??
Conclusions
• UK water infrastructure currently faces risks from a range of specific soil-related geohazards.
• UK water infrastructure is especially at risk from
future climate change and clay-related subsidence (Pritchard et al. (2014))
• UKCP09 probabilistic projections have been
combined with clay-subsidence model to provide future risk scenarios.
• Probabilistic geohazard models can aid the asset management of the UK water network
bbc.co.uk
Acknowledgements
• Anglian Water • EPSRC / ITRC – Doctoral research funding
• Further Info on soil-related geohazards and infrastructure: http://www.itrc.org.uk/outputs/publications/#geohazards
• Soils information and datasets: http://www.landis.org.uk