La Mojana is one of the poorest regions in Colombia and is highly vulnerable to the impacts of climate change, especially floods and droughts. For example, devastating floods in August 2021 affected about 180,000 people, damaged 7,000 hectares of crops, and put 300,000 cattle at risk of drowning or starving. The flood also damaged infrastructure, disrupted public life, and displaced many people from their homes. In the prolonged dry seasons, communities increasingly face water scarcity and see their livelihoods from fishing and agriculture at risk.
La Mojana is also a highly biodiverse region. The complex ecosystem features vast swamps, marshes, forests, and canals, collecting water from three major rivers. Indigenous communities have lived in the region and managed the ecosystem for many years, for example, by creating an extensive network of channels for flood water management. However, these channels have deteriorated over time, and population growth and encroachment on wetlands are increasingly contributing to environmental problems.
Policy-makers, planners and civil society organizations are exploring the use of nature-based infrastructure (NBI) for climate adaptation and sustainable development in the region. They have started restoring channels between rivers and swamps, rehabilitated strategic wetland areas to serve as buffer zones, improved agricultural practices, and started reforestation programs to support the healthy functioning of the ecosystems.
In collaboration with the Colombian Department of National Planning, the International Institute for Sustainable Development (IISD) applied its Sustainable Asset Valuation (SAVi) methodology to analyze the costs and benefits of various infrastructure options and scenarios for flood protection in La Mojana (see Figure 1). These scenarios are compared to a business-as-usual scenario where no additional measures are taken.
Figure 1. Infrastructure options considered in the integrated assessment.
Key Findings
The upgraded dam, the rehabilitation of channels and wetlands, and the sustainable agriculture practices reduce the flood risks in three ways:
- The dam diverts water away from vulnerable areas.
- The interventions increase connectivity so that flood water can reach dedicated retention areas.
- The interventions increase the landscape’s water retention capacity.
Jointly, the dam construction, channel and wetland rehabilitation, and sustainable agriculture could reduce the number of buildings affected by floods by 50% between 2022 and 2050.
Investing in the combination of conventional and nature-based interventions could avoid more than USD 1.26 billion (COP 6,131 billion) in flood damages to buildings, roads, and agriculture over the next 30 years.
The SAVi assessment shows that all of the infrastructure options are investment worthy when the full range of economic, social, and environmental costs and benefits are considered, with benefit-to-cost ratios ranging from 2.07 to 26.1 across the different interventions. For each dollar invested, they generate more than twice that amount in benefits and avoided costs for society. The benefit-to-cost ratio of the combined measures is more than double that of only building the dam. When only the direct project costs and benefits are included in the calculations, none of the infrastructure options appear investment worthy, which underlines the importance of considering the wider societal outcomes.
The integrated cost-benefit analysis also indicates that investing in the nature-based interventions has the potential to create substantial socio-economic benefits. By implementing sustainable agriculture practices, local communities could benefit from USD 516 million (COP 2,509 billion) in additional value from crop production and related labour income, for investments of about USD 191 million (COP 931 billion). As La Mojana is one of the poorest regions in Colombia and is experiencing strong population growth, sustainable agriculture represents a crucial opportunity for sustainable livelihoods and food security.
While all assessed interventions can provide important benefits, combining the infrastructure investments unlocks valuable synergies. If considered separately, the dam construction, channel and wetland rehabilitation, and sustainable agriculture deliver avoided costs and added benefits worth about USD 2 billion (COP 9,806 billion), for investments of USD 486 million (COP 2,362 billion). We also modelled a scenario where all these measures are implemented together. Combining the investments would generate USD 2.91 billion (COP 14,154 billion) in value for society through synergy effects, which is about USD 900 million (COP 4,348 billion) more than the separate measures (see Figure 2).
Investing in the combination of conventional and nature-based interventions could avoid more than USD 1.26 billion (COP 6,131 billion) in flood damages to buildings, roads, and agriculture over the next 30 years.
This finding highlights the importance of taking a systemic perspective in infrastructure planning by considering a portfolio of infrastructure options that includes both natural and grey infrastructure. It also emphasizes the need to adapt tools and modelling approaches for infrastructure planning, valuation, and financing to ensure that wider benefits and costs of such projects are recognized and valued.
Figure 2: Synergistic benefits of jointly implementing dam construction, channel and wetland rehabilitation, and sustainable agriculture.
Key Policy Messages
1. To address flooding in La Mojana, a combination of grey and nature-based infrastructure should be considered to maximize development outcomes.
The expansion of the dam and use of nature-based approaches can effectively divert water from flood-prone areas and increase connectivity and water retention, all of which are crucial to protect local livelihoods from floods. Planners and policy-makers should strategically combine grey and natural infrastructure to ensure the largest benefits for flood protection, ecosystem health, and local livelihoods. Assessing the impact of interventions with systems models can help to better understand important interlinkages and synergies. In addition, interventions need to be planned carefully to avoid inadvertently undermining their individual effectiveness. For example, constructing a dam along the river could block valuable drainage channels, which could be compensated with outlets of the dam that connect the river and the channels.
2. To improve water management in La Mojana, it is important to invest in improved spatial data.
Updated land-cover and land-use maps would be valuable to refine the spatial analysis as they form the basis for creating a more consistent and more detailed time series of such maps. This will, in turn, improve the projections of the ecosystem services and flood risk assessments and facilitate strategic infrastructure planning in La Mojana.
3. Integrating the perspectives of various stakeholders in La Mojana helps ensure that infrastructure decisions consider knowledge from multiple domains.
For example, leveraging Indigenous knowledge about drainage channels holds great potential to improve water management in La Mojana. Planning processes should therefore involve a diverse set of stakeholders at all project stages, from planning to design and implementation. Integrated valuations like the IISD SAVi assessment can ensure that knowledge from different stakeholders informs assessment tools and policies.
4. Creating climate-resilient communities in La Mojana requires more than investment in infrastructure.
Improving both grey and natural infrastructure increases the capacity of the region to deal with floods and droughts, but additional measures are needed to ensure that communities can live safely and sustainably in La Mojana. For example, the development of emergency and evacuation plans, flood proofing of critical infrastructure, and development of recovery plans and disaster funds—all complemented by inclusive planning processes—are important building blocks of climate resilience.
More information about the SAVi assessment of La Mojana is available in a technical report, published next week. The assessment was led by Georg Pallaske, and this article was written by Ronja Bechauf.
