workshop on common criteria for risk area identification in ‘soil...
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Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
A workshop in support of the Thematic Strategy for Soil Protection
Common Criteria for Risk Area Identification in the Soil Framework Directive
BGR, Hannover, 25 April 2007
Soil Erosion
Dick Thompson on behalf of:Bob JonesNational Soil Resources InstituteCranfield University UK
Contributors: Christine Le Bas, Josef KozakAdvisors: Olaf Düwel, Dominique King
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Soil Erosion – points to be covered
Definitions, types, causes and consequences of soil erosionIdentifying areas at riskConclusions
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Definition of Soil Erosion
‘Soil erosion is the wearing away of the land surface by physical forces such as rainfall, flowing water, wind,
ice, temperature change, gravity or other natural or anthropogenic agents that abrade, detach and remove
soil or geological material from one point on the earth's surface to be deposited elsewhere’.
Soil erosion is normally a natural process occurring over geological timescales; but where (and when) the
natural rate has been significantly increased by anthropogenic activity accelerated soil erosionbecomes a process of degradation and thus an
identifiable threat to soil.
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Types of erosion
- Water- Wind- Tillage
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Water erosion
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Water erosion
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Water erosion
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Wind erosion
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Tillage erosion
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Characteristics of soil erosion
• Variable in intensity, scale & nature• Episodic – very often event-driven• Leads to conversion of soil into
sediment • Driven by nature as well as man
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Drivers
Water Rain-splash dislodges soil particles that initially fly through the air (saltation) Rain-flow, Rill-wash cause overland flowSlope wash, Sheet wash cause overland flowWave motion in streams, rivers and lakes cause slumping of bank material
Wind Wind velocity dislodges loose soil particles that become airborne until velocity reduces
Anthropogenic factors, such as:-
Natural factors
Human/climate-induced changes in soil – loss of organic carbon, structure
Tillage and other mechanical influences
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Surface capping
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Livestock
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Topsoil (normal structure)
Dense, compacted layer with lack of soil structure
Topsoil / Subsoiljunction
Compaction (heavy machinery)
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Consequences of Soil Erosion
On-siteRemoval/redistribution of soilLoss of productivityReduction of soil functional capacity
Off-siteSilting of lakes, reservoirs and river coursesDiffuse pollution of soil and water by contaminants and nutrients Destruction of habitatsDamage to property & infrastructure
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Identification of areas at risk
Approaches
1. Empirical - on-site measurement;
2. Modelling – calibrated with real data;
3. Combination of 1 and 2 above.
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
1. Measure soil loss from plots [ field scale] or larger areas (resource intensive and requires long term commitment)
2. Expert judgement/field observation of soil loss from a field, hillslope, river basin or catchment, or other spatial unit (e.g. administrative unit)
3. Measure suspended sediment in rivers, lakes[catchment scale]
Measuring Soil Erosion
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Weather station
Weather station
Sediment traps in place
Pipe from collectors
Collector
General site view
Carcassonne Site
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
We have insufficient field data and the required monitoring networks do not currently exist so:
The assessment of erosion at European scale is only feasible by using mathematical models
Most models attempt to combine:
1. Inherent soil erodibility & landscape (eg slope characteristics for water erosion) - vulnerability2. Drivers & degree of protection provided by vegetation or crops - risk
Advise note:Soil losses estimated from computer models need validation
- we need a monitoring network
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Common CriteriaNatural AnthropogenicParent material/soil: particle size (sand, silt content), susceptibility to crusting, aggregate stability
Tillage-cultivation practices
Topography: slope gradient, length and form
Land levelling, terrace construction
Climate: precipitation, evapotranspiration, temperature, wind speed & direction
Climate change?
Vegetation/Land cover: natural or climax
Land Use/Land cover:arable, grassland/pasture, forest, semi-natural vegetation Land management: cropping systems, irrigation, grazing intensity
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Soil
Rainfall
Temperature
DATA Sources
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Accelerated erosion by running water has been identified as one of the most severe threats to soil in Europe.
Estimated soil loss by rill and inter-rill(water) erosion
Pan-European Soil Erosion Risk Assessment PESERA
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Two critical questions – limits?
What is an ‘accelerated’ rate of erosion?
Is there a ‘tolerable rate’ of soil erosion?
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Some figures
Average rates1- 20 t/ha/yr for Europe
Extreme eventsStorms can erode 50-100+ t/ha/single event
Natural erosion rates:Recent study (Wilkinson and McElroy, 2007) Avg rate for 542million years (Phanerozoic) = 0.42 t/ha/yrAvg rate in Pliocene (most erosive period) = 1.36 t/ha/yr Current riverine flux to global oceans = 1.78 t/ha/yrErosion from present day farmland = 6.36 t/ha/yr
Tolerable erosion rates :< 1 t/ha/yr as a precaution 1.5 t/ha/yr might be acceptable ~ Pliocene = 1.4 t/ha/yr
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Summary and conclusions
Soil erosion is a significant problem in EuropeIt is expected to increase under climate changeWater erosion is the most widespread formIt is right that the SFD covers its control
Tolerable erosion rates - policy process to decide [but] soil loss >1 t/ha/yr = accelerated over natural rate
Soil erosion should be monitored through anetwork of fully instrumented measuring sites
should be established across Europe
Workshop on Common Criteria for Risk Area Identification in the Soil Framework Directive, BGR, Hannover, 25 April 2007
‘Soil Erosion’
Thank you!
Danke schön!