Introduction

This sections introduces the yield reduction caused by soil erosion. The terrain suitability assessment is fully implemented based on GAEZ v4 model documentation with an updated algorithm according to GAEZ methodology. The assessment is implemented based on terrain slope condition, and rainfall intensity. The overview of Module V: Terrain Constraints is shown in the figure below.

In v2.3, users are required to provide the terrain constraint factors as excel sheet instead of python script mode.

Figure: Overview of Module V: Terrain Constraints

---

Mandatory Settings

Initialization of M5 Object Class Creation

Firstly, an object class TerrainConstraints must be delcared.

from pyaez import TerrainConstraints
terrain = TerrainConstraints.TerrainConstraints()

Input

Arguments	Description	Unit	Data Type
None	-	-	-

Output

Arguments	Description	Unit	Data Type
None	-	-	-

---

Importing Terrain Reduction Parmaeter Excel Sheets

Two separated excel files of terrain reduction factors must be prepared, corresponding to rainfed and irrigated conditions, before importing into the object class. The setting is explained in Data Preparation.

Once the preparation is done, the following function can be executed.

terrain.importTerrainReductionSheet(irr_file_path, rain_file_path)

Input

Arguments	Description	Unit	Data Type
irr_file_path	Full file path of terrain constraints excel file for irrigated condition	-	String
rain_file_path	Full file path of terrain constraints excel file for rainfed condition	-	String

Output

Arguments	Description	Unit	Data Type
None	-	-	-

---

Importing Climate and Slope Data

This function allows users to set up monthly/daily precipitation and terrain percent slope data. Make sure the precipitation has 12 layers for monthly or 365/366 for daily data.

terrain.setClimateTerrainData(precipitation, slope)

Input

Arguments	Description	Unit	Data Type
precipitation	Daily/Monthly total precipitation	mm/day	3D-NumPy Array
slope	Percent Slope	%	2D-NumPy Array

Output

Arguments	Description	Unit	Data Type
None	-	-	-

Calculate Fournier Index

This functions calculates Fournier Index (FI), a index to quantify the rainfall intensity. FI represents a simple index indicating the potential of soil erosion based on monthly precipitation.

terrain.calculateFI()

Input

Arguments	Description	Unit	Data Type
None	-	-	-

Output

Arguments	Description	Unit	Data Type
None	-	-	-

---

Optional Settings

Setting the Study Area Mask

This function is set up as an optional step which set up the mask layer as input which reduces the computation time outside the pixels of considerations.

# Set up mask for the study area (country, regional, or local)
terrain.setStudyAreaMask(admin_mask, no_data_value)

Arguments	Description	Unit	Data Format
admin_mask	Mask Layer/Region of Interest	Binary(0,1)/Categorical(1,2,...)	2D NumPy Array
no_data_value	Value of mask layer to skip calculation	Mask value from the layer.	Integer

__

Major Functionalites

Applying Terrain Constraints

Once all the mandatory settings are done, users can run this function which executes the terrain-related yield reduction factors.

yld_out = terrain.applyTerrainConstraints(yield_in, irr_or_rain)

Input

Arguments	Description	Unit	Data Type
yield_in	Yield before applying the terrain-related reduction factor. (Either irrigated or rainfed).	kg/ha	2D-NumPy Array
irr_or_rain	I for irrigated, R for rainfed	-	String

Output

Arguments	Description	Unit	Data Type
yld_out	Terrain adjusted yield map.	Same as yield_in	2D-NumPy Array

---

Terrain Suitability Map (Fc5)

This function returns the terrain suitability map (fc5) after applying the terrain constraint function. Based on the setting from applyTerrainConstraints, the fc5 map can be representative for either rainfed or irrigated. Fc5 values ranges from 0 (Not Suitable) to 1 (Very Suitable).

fc5_map = terrain.getTerrainReductionFactor()

Input

Arguments	Description	Unit	Data Type
None	-	-	-

Output

Arguments	Description	Unit	Data Type
fc5	Terrain reduction factor	-	2D-NumPy Array

---

Fournier Index (FI)

This function extracts the Fournier Index (FI) map after the execution of calculateFI function.

fi = terrain.getFI()

Input

Arguments	Description	Unit	Data Type
None	-	-	-

Output

Arguments	Description	Unit	Data Type
fi	Fournier Index	-	2D-NumPy Array

---