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Invest 2.2.1 Sediment 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 – Multiple services – Evaluate change – Spatially explicit – Biophysical & monetary – Production functions – Open source Models Simple Complex Data Tier 0 Tier 1 Tier 2 Tier 3 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 Slope Conservation factor Erosivity Soil Erodibility Crop factor Sediment loads Loading Valuation Critical Loading Time 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 Limitations Predicts 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 Simulated vs Observed Soil loss (103 t) 45000 y = 122.55x R² = 0.74 p < 0.01 Simulated soil loss (103 t) 40000 35000 30000 25000 20000 15000 10000 5000 0 0 50 100 150 Observed soil loss (103 t) 200 250 Hainan Island, China RNF 2008 NRPE IEM RNF 1998 350 2008 NRPE CEM RNF 300 300 Soil loss (103 t) Soil Loss (103 ton) 400 400 250 200 200 150 100 100 50 0 0 Nandujiang Nandujiang Wanquanhe Wanquanhe Changhuajiang Changhuajiang Scenarios for Mine Expansion in Columbia Current Mines Permits Pending Permits Granted All possible permits Mining in Columbia Sediment Load (t/ha/yr) Permits Granted Permits Pending All possible Permits Mining in Columbia High Impact Zones should avoided Permits Granted Permits Pending All possible Permits Coming up soon in InVEST Sediment delivery ratio Gully and bank erosion (tier 0) West Coast East Coast Dam retention Multiflow algorithm Belize Mexico Will run faster Ecuador Colombia Amazon Improved Length SlopeBasin equation Tanzania Indonesia 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? USLE R.K .LS .C.P 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 Inputs Land Use/Land Cover Streams Vegetation retention, land practice and management Used to determine where sediment flows to Slope Digital elevation model, slope threshold Watershed Areas Main and sub for point of interest and water quality analysis Erosivity Reservoir Features Based on intensity and kinetic energy of rainfall Dead volume, lifetime of reservoir, allowed load Erodibility Soil detachment and transport potential due to rainfall Biophysical Outputs Potential Soil loss Calculated from USLE per sub-watershed Sediment Exported Calculated per subwatershed Sediment Retained Calculated per subwatershed Used in valuation Valuations Valuation Inputs Watershed Areas Main and sub for point of interest and water quality analysis Sediment Exported From biophysical analysis Sediment Retained From biophysical analysis Sediment Valuation Reservoir dredging costs Valuation Outputs Value of Sediment Removal for Dredging Value of Sediment Removal for Water Quality How Does it Work?... USLE R.K .LS .C.P • • • • • • • 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?... USLE R.K .LS .C.P For low slopes 𝐿𝑆 = 𝑓𝑙𝑜𝑤𝑎𝑐𝑐∗𝑐𝑒𝑙𝑙𝑠𝑖𝑧𝑒 𝑛𝑛 * 22.13 sin(𝑠𝑙𝑜𝑝𝑒∗0.01745) 1.4 0.09 ∗ 1.6 For high slopes 𝐿𝑆 = 0.08 ∗ 𝜆0.35 ∗ 𝑠𝑙𝑜𝑝𝑒 0.6 • 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. 𝑆_𝑟𝑒𝑡𝑎𝑖𝑛𝑥 = 𝑅. 𝐾. 𝐿𝑆. 𝐶. 𝑃 − (𝑅. 𝐾. 𝐿𝑆) 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 Cumulative Sediment Yield Value of removed sediment at pixel x: 𝑇−1 𝑃𝑉𝑆𝑅𝑥 = 𝑡=0 𝑇𝑜𝑡_𝑟𝑒𝑡𝑎𝑖𝑛𝑥 ∗ 𝑀𝐶 1+𝑟 𝑡