Methodology technical feasibility NbS 1

This map aims to showcase which areas are suitable for flood-based agriculture projects. Our methodology for analysing suitable areas for flood-based agriculture is based on two guiding principles:

• The area is currently protected by a dike and is therefore disconnected from the flood plain.

• The current biophysical conditions of an area are suitable for the specific agricultural practice.

Approach

The spatial potential of the selected NbS types is mapped by overlaying different geospatial datasets, like hydrologic, soil and climatic data. This provides a first high-level indication to the effective geographic scalability of NbS. The suitability for a specific NbS is, where possible, classified in 4 classes: highly suitable, moderately suitable, marginally suitable and not suitable.

The methodology applied for this study is derived from previous conducted studies by Royal HaskoningDHV for WWF on "Upscaling of Flood-Based Agriculture in Mekong Delta in Viet Nam" and for The World Bank Group on "Assessing Land Suitability, Water Management Conditions, and Climate Risks in the Mekong Delta Region (2021-2030), with an Outlook to 2050."

All suitability factors that are described below were classified into two categories, an area is either suitable or not suitable given that suitability factor. Should any of the factors render an area unsuitable, regardless of the scores from other factors, the area is automatically labelled as unsuitable for this NbS. Inundation depth further classifies an area in marginally, moderately or highly suitable for flood-based agriculture.

The suitability class - highly, moderately or marginally suitable, thus depends on two factors: 

• If the area is suitable given all suitability factors.

• If an area is highly, moderately or marginally suitable given the inundation depth suitability factor. 

Suitability components for Flood-based Agriculture

Inundation Depth

The flood with an exceedance probability of 10% is used to determine the area classification related to inundation conditions. The classification of flood depth in the Mekong Delta is based on the experience in agricultural production and similar flood studied carryout by Southern Institute of Water Resources Research for the Mekong Delta. The following 5 classes have been identified within this classification:

• No flooding

• Low flood (inundation depth < 50cm)

• Medium flood (inundation depths of 50-100 cm)

• High flood (inundation depth 100 - 200 cm)

• Very high flood (inundation depth >200 cm)

The three tables below describe the classification scheme used per suitability factors, how the classified suitability factors are grouped into suitability score bins, and the sources of the suitability factors.