invest 2.2.1 sediment retention model yonas ghile
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Invest 2.2.1Sediment Retention model
Yonas Ghile
Talk Overview
Why care about ecosystem services?
InVEST
Sediment Retention Model
Hands-on Exercise
Case study
What are Ecosystem Services?
InVEST: Science in a Simple Tool
Integrated Valuation of Ecosystem Services and Tradeoffs
InVEST Attributes
– Evaluate change
– Biophysical & monetary
– Open source
– Multiple services
– Spatially explicit
– Production functions
Tier 1 Tier 2 Tier 3
Models
Data
Simple Complex
Tier 0
Why sediment retention model?
Soil erosion and sediment can cause:• Decrease in agricultural productivity,• Degradation of fish habitat and aquatic life, • Risk of structural failures• water quality degradation.
Increase maintenance cost
Questions you get answers
Where are the Sediment sources?
Where are the Sediment retention
areas?
How much is retained?
What is the Value of this retention?
Informs Policy Makers to Focus protection on areas that retain the most and pollute the
least
Design management practices that lead to maximize retention
Create payment programs to get most return on investment
(with tier2)
Identify places where other economic activities will conflict with
erosion control
How much costs can be avoided under future management or
conservation plans?
Sediment Retention Model
Erosivity
Sediment loadsCrop factor
ConservationfactorSlope
Soil Erodibility
Valuation
Time
Load
ing
Critical Loading
Strengths
Uses readily available and minimum data.
Simple, applicable and spatially explicit
Link the biophysical functions to economic values
Values each parcel on the landscape
LimitationsPredicts erosion from sheet wash alone
Considers only individual effect of each variable
Relies on retention and filtration efficiency values for each LULC
Neglects the role of topography, soil, climate in the retention
processes
Accuracy limited in mountainous areas
Model Calibration and Testing
Sensitivity Analysis to identify most sensitive parameters
Model Calibration using long term average actual data
Find USLE parameters within acceptable ranges
Validate Model by conducting comparisons with observed data or
other model output
Hainan Island, China
y = 122.55xR² = 0.74p < 0.01
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
0 50 100 150 200 250
Sim
ula
ted
so
il l
oss (
10
3t)
Observed soil loss (103 t)
Simulated vs Observed Soil loss (103 t)
RNFRNF 2008 NRPE IEM
0
50
100
150
200
250
300
350
400
Nandujiang Wanquanhe Changhuajiang
Soi
l los
s (1
03t)
1998 2008 NRPE CEM RNF
400
300
200
100
0
Soil
Loss
(1
03
ton
)
Nandujiang
Wanquanhe
Changhuajiang
Hainan Island, China
Scenarios for Mine Expansionin Columbia
Current Mines
Permits Granted
Permits Pending
All possible permits
Permits Granted Permits Pending All possible Permits
Sediment Load (t/ha/yr)
Mining in Columbia
Mining in Columbia
High Impact Zones should avoided
Permits Granted Permits Pending All possible Permits
Coming up soon in InVEST
Tanzania
West Coast
Amazon Basin
Mexico Colombia
Ecuador Indonesia
Belize
East Coast
Sediment delivery ratio
Gully and bank erosion (tier 0)
Dam retention
Multiflow algorithm
Will run faster
Improved Length Slope equation
Hands-on Session
Run the soil loss model
Hands-on Session
Run the valuation model
Hands-on Session
Think about how you would use the Sediment Retention Model in your work?
How Does it Work?
PCLSKRUSLE ....
Natural Characteristics: R – Rainfall Erossivity K – Soil Erodibility LS – slope-length factor
Land Use Land Cover Management Practices: C – conservation factor P – Practice factor
Biophysical InputsLand Use/Land CoverVegetation retention, land practice and management
SlopeDigital elevation model, slope threshold
ErosivityBased on intensity and kinetic energy of rainfall
ErodibilitySoil detachment and transport potential due to rainfall
Watershed AreasMain and sub for point of interest and water quality analysis
Reservoir FeaturesDead volume, lifetime of reservoir, allowed load
StreamsUsed to determine where sediment flows to
Biophysical Outputs
Potential Soil lossCalculated from USLE per sub-watershed
Sediment ExportedCalculated per sub-watershed
Sediment RetainedCalculated per sub-watershed
Used in valuation
ValuationsValuation Outputs
Value of Sediment Removal for Dredging
Value of Sediment Removal for Water Quality
Watershed AreasMain and sub for point of interest and water quality analysis
Sediment ExportedFrom biophysical analysis
Sediment RetainedFrom biophysical analysis
Sediment ValuationReservoir dredging costs
Valuation Inputs
How Does it Work?...
PCLSKRUSLE ....
• Data inputs for Soil Erodibility• Percent Silt, %Slt• Percent Very Fine Sand, %VFS• Percent Clay, %Cly• Percent Organic Matter, %OM• Soil Structure Code, SC• Profile Permeability, PP
How Does it Work?...
PCLSKRUSLE ....*
For low slopes
For high slopes𝐿𝑆=0.08∗𝜆0.35∗ 𝑠𝑙𝑜𝑝𝑒0.6
• LS: Slope length factor
• Original LS was calculated from plots of 72.6 feet long and 9% slope
• The steeper and longer the field the higher is the risk of erosion.
How Does it Work?...
Hydraulic connectivity model
How Does it Work?...
1.)
2. Removal of sediments by vegetation along the flowpaths is calculated as follows
How Does it Work?...
Sediment Yield is defined as the potential soil loss from terrestrial sources that might get into a water body
Value of removed sediment at pixel x:
cornforest
wheatforest
S
tream
Cumulative Sediment Yield
𝑃𝑉𝑆𝑅𝑥=∑𝑡=0
𝑇−1 𝑇𝑜𝑡𝑟𝑒𝑡𝑎𝑖𝑛𝑥∗𝑀𝐶
(1+𝑟 )𝑡
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