International Levee Handbook Webinar Series
Chapter 7: Site Characterization and Data
Requirements
Presented by:
The United States Levee Safety Coalition
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Chapter 7 - context
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7 Site characterisation and
data requirements
• Chapter has two principal themes
– Actions on levees
• Determination of hydraulic actions for fluvial, coastal and shoreline, and
estuarine levees at the toe
• Human actions on levees
– Assessment of influence of physical characteristics of the levee
and environs
• Geotechnical
• Fluvial, coast and shoreline, and estuarine dynamics
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7.1 Principles of site characterisation
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7.1 Principles of site characterisation
• Needs for characterisation
• Adopt a phased approach to characterisation
• Desk study
– Undertaking and sources of information
– Ground “truthing” by walkover survey
• Implementing investigations
– Roles of personnel involved and H&S
• Reporting
– Desk study data, meta-data, hydraulic, morphology and
geotechnical data, and preservation and presentation of data
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7.1 Principles of site characterisation
• Phased approach – typically three
– Reconnaissance (Initial assessment of viability)
• Utilising existing information
– Feasibility (Develop better understanding)
• Detailed hydraulic data and modelling
• Limited geotechnical investigations to support assessment
– Detailed (Final design)
• Detailed geotechnical
assessment
• Update or refine
hydraulic data and
modelling
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7.1 Principles of site characterisation
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7.2 Morphological, hydraulic and
other natural actions on levees
• Riverine, coastal and
shoreline, or estuary
settings must consider:
– Interaction between levees and
environmental factors
– Influences of seasonal change
and extreme events
– Influences of long-term change
– Actions from other natural
processes
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7.2 Morphological, hydraulic and
other natural actions on levees
• Actions from other natural processes include:
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Windblown sediments
Wind on vegetation
Seismic
Ice on river
Rainfall
Sun
Climate change
Choke vegetation
Forces on slope
Body forces & liquefaction
Water levels & damage
Soil strength & erosion
Desiccation & kill vegetation
Levee structure, as
above, & hydraulic actions
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7.2 Morphological, hydraulic and
other natural actions on levees
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7.3 Morphology and hydraulic actions
for riverine levees
• Understanding river characteristics
• Determination of hydraulic actions
– Data needed
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Measurement of flows and water levels
Sediment movement
Bed roughness and geometry
Wind
Water levels and waves
– Methods of determining hydraulic
actions
• Flow and water level analysis
• Modelling of hydraulic processes
• Influence of shipping and ice
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7.3 Morphology and hydraulic actions
for riverine levees
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7.3 Morphology and hydraulic actions
for riverine levees
• Rivers are dynamic systems that:
− Are a product of their
environment
• Soils and geology
• Gradients (slope of landscape)
• Hydrology (rainfall and runoff)
− Respond to variable
hydraulic actions
• Lateral movements
• Vertical movements
• Volume and Rate of flow
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7.3 Morphology and hydraulic actions
for riverine levees
• Levees may change hydraulic conditions and alter
the dynamic equilibrium of these systems
• Assessment of hydraulic actions is essential to
establish present and expected behaviour
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7.4 Morphology and hydraulic actions
for coastal and shoreline levees
• Understanding coastal characteristics
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7.4 Morphology and hydraulic actions
for coastal and shoreline levees
• Determination of hydraulic
actions
– Data needed
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Sediment movement and bathymetry.
Pressure and wind
Water levels and waves
Marine currents and tides
Tsunamis
– Methods of determining hydraulic actions
• Extreme water level and wave analysis
• Joint probability
wave and water level
• Uncertainty in data and analysis
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7.4 Morphology and hydraulic actions
for coastal and shoreline levees
• Coastal and shoreline systems are dynamic and
highly complex
• Hydraulic loads acting on coastal levees vary:
– Geographically
– Over time (daily, monthly, seasonal, decadal and longer-term)
– Comprise various combinations of water levels, currents, and waves
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7.4 Morphology and hydraulic actions
for coastal and shoreline levees
• Necessary to know extreme water levels, waves,
currents, and morphological response
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7.5 Morphology and hydraulic actions
for estuarine levees
• Principle concern derives from how estuary
characteristics influence water levels, velocities and
wave heights in transition between river and coast
• Estuarine morphology
– Processes originate from both sea and river sources
– Dependant on shape and bathymetry of estuary
– Series of questions presented (Table 7.38) to assist in analysis of
estuaries
• Hydraulic action on estuarine levees
– Determining hydraulic actions on estuarine levees involves a
combination of river and coastal analysis techniques
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7.5 Morphology and hydraulic actions
for estuarine levees
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7.5 Morphology and hydraulic actions
for estuarine levees
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7.6 Human actions on levees
• Load types, and loading assumptions and
restrictions. Categories considered:
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Recreation
Terrorism
Boat traffic
Unplanned structures
Transport
infrastructure
– Construction, maintenance and
operational actions
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Plant loads
Temporary stockpiles
Changes in geometry
Secondary functions
Crest raising
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7.7 Ground investigation for levees
• Overview of planning and conducting a GI
• GI requirements relative to
– Failure modes: Failure process, investigations and monitoring
– Different levee scenarios: Condition assessment, improvement
works and new levees
– Structures and material assessment
• GI valuation through
– Pre construction trials
– Visual observation during construction
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7.7 Ground investigation for levees
• Considerations when investigating existing
levees as a result of past activities
– Construction
• Heterogeneous internal structure, including structural elements, resulting
from historic raising and widening.
– Improvement
• Side slopes and crest many be formed from different material with could
include ‘dredgings’
– Repair
• Seepage mitigation or breach repairs may include: aprons, sheet piles or
deep soil mixing
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7.7 Ground investigation for levees
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7.8 Geotechnical parameters
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7.8 Geotechnical parameters
• Determination of parameters
through
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Typical values
Empirical correlations with index properties
Direct measurement: laboratory and in situ
Geophysics
• Properties and parameters
– Compressibility
considered
– Index
– Compaction
– Shear strength
– Permeability
– Erodibility
• Determination of characteristic values
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7.8 Geotechnical parameters
• Selection of a characteristic value is the probably
the single most important geotechnical design
task
• Some considerations in selecting a value:
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Codes used
Degree of conservatism
Applicability to limits state
Strain hardening or softening
Derivation of correlations
Data quality and quantity
• Lower characteristic value: 95% probability of
being exceeded by the spatial average
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7.9 Site investigation methods
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7.9 Site investigation methods
• Surface information
– Terrain
– Surface cover
– Bathymetry
– Sediments
• Hydraulic gauging methods
Rivers:
– Gauge height
– Discharge
– Sediment load
Coasts and Estuaries:
– Tide and wave height
– Currents
– Sediment load
• Geotechnical information
– Geophysics
– Intrusive
– Sampling
– Instrumentation
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7.9 Site investigation methods
• Spatial distribution of intrusive investigations: Adequate to
characterise both the levee and the foundations
• Phased approach:
Desk study
Non intrusive
Intrusive
• Guidance in Codes and Standards on
spacing but include targeted
locations
• Investigate lateral variations in
ground condition not just along
the levee alignment
– CPT
– Targeted
boreholes
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7.9 Site investigation methods
• Geophysics
– Includes broad spectrum of techniques: airborne, onshore
surface and borehole, and water based
– Integral part of a phased investigation
– Gain information to target and infer conditions between points of
intrusive investigation.
– Fast screening of sites for feasibility
– Condition assessment of exiting levees
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7.9 Site investigation methods
• Application of surface geophysics to exiting levees.
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7.9 Site investigation methods
• Intrusive investigations
– Levee foundations typical comprise a combination of high
permeability soils and low strength high compressible soils
under conditions that may present difficult access.
– Base equipment, drilling and sampling techniques need to take
account of these factors to obtain required data.
– Special considerations
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Close to water
Ground stability
Contamination
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UXO
Flora and fauna
Biohazards
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7.9 Site investigation methods
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7.9 Site investigation methods
• Instrumentation
– To better understand the levee and foundations
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Condition
Interactions
Construction
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Validate
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design and assumptions
ground characteristics
• Considerations in the selection, installation and
monitoring
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Nature and magnitude
Redundancy
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Installation records
Base line readings
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Base line readings
Reading and records
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7.9 Site investigation methods
• New and involving techniques
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Thank you
Chapter 7 Team Leads:
Shaun Wersching
CH2M Hill
E: Shaun.Wersching@ch2m.com
Andy Gaines
USACE
E: Roger.A.Gaines@usace.army.mil
To download the International Levee Handbook
go to: www.ciria.org/ILH
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International Levee Handbook Webinar Series
Chapter 7: Site Characterization and Data
Requirements
Repeat Chapter 7 Webinar: 17 June 2015 - 4 PM EDT
Chapter 8 Webinar: 7 July 2015 – 12 noon EDT
www.ciria.org/ilh