By Sebastien Gachot, Gines Suarez, Bruno Jaquet and Carmine Paolo de Salvo
Water is the most essential element to life on earth, yet too much water all at once can have devastating effects. One country very familiar with the destructive force of water is Haiti, which has a particularly high exposure to natural disasters, but very low capacity for natural disaster risk management.
In 2008, for example, within less than a month, Haiti was hit by three hurricanes and a tropical storm. The damage caused by the resulting floods and erosion was massive: Hurricanes Gustav and Hanna alone caused an estimated US$900 million in damage that year, according to the Haitian government.
In 2009, the IDB financed the construction of key infrastructure as part of the Natural Disaster Mitigation Program I (PMDN I) with the goal of reducing the environmental and socioeconomic vulnerability to natural disasters of the population living in the Artibonite and Cavaillon watersheds.
Once the project was completed the team faced some serious challenge: How can you reliably analyze the impact of natural disaster mitigation measures when data are scarce? How can you know that the benefits are higher than the costs of the project? And how can the Bank use the findings to improve future operations?
What Did Natural Disaster Mitigation Program (PMDN I) Deliver?
PMDN I financed the construction of four downstream riverbank protection works along the Artibonite and Cavaillon Rivers. The powerful current of the Artibonite River caused erosion along the canals built alongside the river to feed the country’s largest irrigation system.
Without these canals, rice and vegetable producers working an area that spans 15,862 hectares would have to rely on rainwater to irrigate their fields – a much less reliable source of water, and a haphazard system that would eventually lead to agricultural losses.
To prevent the collapse of these canals due to erosion, PMDN I financed the construction of three concrete retaining walls that can reach up to nine meters in height, commonly known as “Berlin Walls”.
PMDN I also financed the construction of gabion walls (metal cages filled with rocks) along the downstream river-bank of the Cavaillon watershed to protect the town of Maniche.
The town had experienced significant economic losses, particularly in the agricultural sector, as a result of frequent exposure to flooding.
How Can We Know Whether the Project Was Effective?
After investing US$13.9 million in the infrastructure component of the project, the Haitian government and the IDB wanted to measure the effectiveness of the infrastructure built under PMDN I before contemplating a second phase of the project.
A rigorous evaluation would fulfill two purposes: first, to estimate the benefits of what had been done, and second, to facilitate decision-making regarding the second project phase. However, evaluating infrastructure projects poses three big challenges for evaluators.
First, it is very difficult to find a comparable population exposed to a similar event: that is, to construct a counterfactual.
Second, the infrastructure financed by PMDN I was built to mitigate the effects of natural disasters—random events that cannot be planned or replicated.
Finally, the lack of data intensifies the first two challenges and makes it difficult to establish baselines and follow-ups.
Given these challenges, the PMDN I evaluation team decided to assess the benefits of the infrastructure measures through a cost-benefit analysis in order to evaluate the cost-effectiveness of each infrastructure alternative.
What Methodologies Were Used?
To assess the works to prevent erosion of the canals in the Artibonite watershed, the evaluation team conducted a technical diagnosis of the state of the canals before the project, to establish a baseline before anything new was built. The results showed that the canals would have collapsed within an average duration of five years.
To evaluate the agricultural losses that would result from the destruction of the canals, the team incorporated data in the 