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