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