Dredged silt from the Suriname River: waste or beneficial material? The Weg naar Zee project, funded by Partners for Water, investigated whether silt dredged from the Suriname River could be used to address coastal erosion and mangrove losses along the Suriname coast. Last month, the feasibility study concluded with promising results. Below, Bob Smits from consortium partner Deltares explains the potential of dredged silt.

About 8 years ago, Nature-based Solutions Advisor Bob Smits completed his master’s thesis on mangrove restoration at the independent knowledge institute Deltares. Since then, he has developed his expertise in coastal protection and management, particularly in sediment transport. In the Weg naar Zee project, Bob serves as the technical lead and project coordinator.

The Weg naar Zee feasibility study was conducted in collaboration with Boskalis, Conservation International Suriname, InterConnect and the Anton de Kom University of Suriname.

Natural buffer

The coastal area of Weg naar Zee is an intertidal zone nearly two kilometres wide, located directly west of the Suriname River mouth. “The coastal area used to be covered with mangroves,” Bob explains, “but over the past decades, it has eroded significantly due to changing land use, leading to the disappearance of almost all mangroves.” These mangroves served as a natural buffer against erosion and flooding. “With the loss of this buffer, flooding now occurs regularly.”

However, the Suriname River is being deepened to improve navigation, releasing large amounts of silt. “Currently, this material is being released into the ocean, but it is actually a valuable resource that can be utilised,” says Bob. “With this project, we aim to investigate whether we can use this dredged material to combat further erosion.”

Silt, sand, and mangroves

“We have some interesting findings from the analysis of the historical coastal development,” Bob says. “Sand appears to play a significant role in the natural restoration of mangrove trees. This can be observed in an area west of Weg naar Zee, where mangroves have returned without active human intervention. We suspect this is due to the natural formation of sandbanks in the intertidal zone, which cause the area behind them to fill with silt, creating an ideal habitat for mangroves.” However, no sandbanks are being formed on the foreshore of Weg naar Zee. “This is most likely caused by previous sand extraction east of the Suriname River and damming upstream of the river.”

Stimulating mangrove habitat

“The potential role of sand is a significant insight that we incorporate into our recommendations,” says Bob. “We see the possibility of placing artificial sandbanks, which would allow us to fill the area behind them with the dredged silt.” This solution would improve the natural conditions for a mangrove habitat, enabling the trees to grow again and form a natural buffer. He continues, “Reusing silt from dredged material is already being done in several places, and is widely acknowledged as a promising concept. However, this combination of using dredged silt and sand for the benefit of mangrove restoration and erosion control is still new.”

Valuable collaborations

“During the research, we involved local stakeholders, such as the Ministry of Public Works and local residents,” notes Bob. “Not only are they the problem owners, but they also possess a lot of local knowledge that we can combine with our international experience. We also owe a great deal to the Dutch Embassy in Suriname, which helped us significantly in arranging meetings with the Ministry of Public Works.”

“I believe the most important aspect of collaboration is to have mutual respect and to be open to each other’s experiences and knowledge,” says Bob. “As a Dutch entity, I view challenges and solutions with my Dutch framework. To develop a solution that is adapted to the local context, it is essential to ask for input and knowledge from local parties and stakeholders and to truly work together towards a collaborative resolution.”

What’s next

“The results have been well received by the Ministry of Public Works and the local residents,” says Bob. As a follow-up to this feasibility study, the consortium would like to initiate a pilot project and is currently exploring available financing opportunities. As Bob explains, “The situation of coastal erosion and mangrove loss we have investigated is similar to the rest of the Surinamese coast and also to that of neighbouring countries Guyana and French Guiana. So if our planned pilot-project is successful, there are plenty of opportunities to scale it up.”

How can degraded farmland in the Surinamese jungle be regenerated? Johan Tijms from agricultural mechanisation company Tijms Mechanisatie VOF can explain. Together with consortium partner Attro Trading Africa, he is addressing Suriname’s drought and salinisation challenges through an innovative pilot project funded by Partners for Water. Discover how they are bringing soil back to life through an affordable and effective approach.

Johan Tijms, director of Tijms Mechanisatie VOF, has been working in the international field of soil regeneration and sustainable irrigation systems for over 25 years. From his office in Geesbrug, he elaborates on the innovative ‘Precise Irrigation Systems’ project. Together with the business consulting and project development organisation Attro Trading Africa, he aims to provide sustainable solutions for problems in agriculture arising from poor soil conditions. In Suriname, the consortium is tackling these challenges through a pilot project funded by Partners for Water. This pilot is testing a solar-powered, sensor-controlled drip irrigation and desalination system designed to address local drought, salinisation and flooding issues, ultimately rehabilitating degraded agricultural land owned by an indigenous Surinamese community.

Drought and salinisation

“Due to drought and unsustainable farming practices, Surinamese agricultural land is rapidly becoming comparable to concrete,” says Johan. “In some areas, the soil is so degraded that it doesn’t absorb water anymore. This causes water to accumulate, leading to both flooding and unusable farmland.” Suriname suffers not only from drought but also from salinisation. “The salt content of groundwater in Suriname is often too high for irrigation practices, leading to crop failures and threatening livelihoods. For instance, the members of the indigenous community where we are conducting the pilot project cannot sustain themselves with their conventional farming practices and must buy additional food from the market.”

From concrete to sponge

“Our solution creates usable irrigation water and turns soil into a water-absorbing sponge,” says Johan. “We achieve this through a drip irrigation system which applies water slowly and efficiently at the root zone of the plants. By doing so, it reduces the amount of runoff and therefore soil erosion.” In addition, the consortium desalinates ground water by using a desalination machine that utilises calcium carbonate. Johan explains: “This method is more cost-effective than others, such as reverse osmosis, due to its lower energy consumption and cheaper materials.” Both the drip and desalination machines are powered by solar panels. “All together, this makes the solution affordable for the relatively poor local community.”

In practice

“The piece of agricultural land we are regenerating covers an area of about five hectares and is located in the middle of the Surinamese jungle. It belongs to an indigenous community of about 300 people.” Johan explains that the land had been declared unusable. “In practice, an unusable piece of farmland means new land will be cleared by cutting down trees. When that land also becomes unusable, the same cycle is repeated. Now that the local community is receiving tools and training to keep the land farmable, not only are their livelihoods improving, but consistent deforestation is also prevented.”

A self-sustaining project

Tijms installed the machines together with Attro. “We train the users to maintain the machines themselves and we’re ready to assist whenever necessary. For instance, a water pump broke down initially because it had pumped up too much sand. We decided to get on a plane with new parts to repair the pump ourselves,” says Johan. He continues: “The success of such a project depends on the commitment and effort from both you and the users. If both parties are dedicated to its success, then you ensure it happens.”

“We also provided financial and business training to prepare the community for maintenance costs,” notes Johan. “Essentially, the installation should facilitate enough harvest to not only sustain livelihoods but also sell crops at the market. This enables the community to save money to replace certain installation components when they near the end of their life cycle. This way, the project becomes self-sustaining.”

Successful collaborations

“So far, the project has been a great success, and we owe much of that to some fantastic collaborations,” notes Johan. “For instance, the Dutch Embassy and the Ministry of Agriculture, Livestock and Fisheries in Suriname have actively helped us with their network and by connecting us with the participating community. Additionally, the community leader was incredibly motivated. Thanks to her dedication and involvement, the project has been embraced by the whole community.” Johan continues, “our collaboration with Partners for Water has also been incredibly valuable. The Partners for Water team has provided significant support, always responded quickly, and demonstrated their commitment to the successful completion of this project in every way.”

What’s next?

“In November, we will complete the project. So far, it seems to be very successful! Based on soil samples, we see that desalination is working and the soil is becoming nutrient-rich and porous again. Additionally, the local community is already selling products at the market.” The solution has significant potential for scaling up both within Suriname and internationally. Johan notes that they already plan to implement parts of this concept in another region of Suriname. “Through the drip irrigation system in combination with a bio enzyme, we plan to clean the soil of Fusarium, a common fungus in banana plants, in certain banana plantations in Suriname.”