Practical Implementation of Nature-Based Solutions (NbS) in Upstream Welang Watersheds

Nature-based solutions (NbS) are increasingly recognized as an essential strategy to address water and erosion challenges in watersheds. These solutions harness natural resources to tackle various water and soil issues. In areas where traditional infrastructure may be expensive, NbS offers a sustainable and cost-effective alternative that is easily replicable by local governments and communities.

In the upstream area of Welang Watershed, East Java, Indonesia, the NbS approach was applied through co-construction with the local community by employing a 3R methodology (retention, recharge, and reuse of water) through creation of simple gully plugs. These structures made from locally available materials like bamboo, stones and branches, serve to collect and temporarily store water during high rainfall flows, retain sediments and materials washed into the channel, and slow down small, concentrated flows.

Utilizing natural materials available in the area as gully plugs (left: bamboo, right: stone)

1. In Surorowo, the upstream area of Welang on the side of Mount Bromo, the project marked the communities’ first experience participating in an international project. Village officials played an important role in encouraging broad community participation. Two Focus Group Discussions involving various stakeholders were held to explain the value of the project and the interventions, to build trust and gain commitment of the community. Over two months of activities, at least 28 different gully plugs and gabions were installed on community land and initiated directly by the community.
2. The project location in Wonosari, the upstream area of Welang on the side of Mount Arjuno, is directly managed by the Wonosari Tea Plantation, making it easier to mobilize and cooperate with the workers. In just 12 working days, a total of 145 simple gully plugs made of stones, tree branches, and bamboo of various sizes were constructed.

Stakeholders involvement in demonstration activities

Institutional support
A Memorandum of Understanding (MoU) on sustainable water resources management in East Java was signed between the East Java Provincial Natural Resources and Public Works Agency (PUSDA), the government implementing agency of the project, and Perhutani, a state-owned enterprise managing the implementation site. This ensured stakeholder alignment and paved the way for replicating NbS across the province.

Monitoring and evaluation
Once implemented, effective monitoring becomes essential for tracking the progress of the installed structures and demonstrating their effectiveness. Field observations conducted by the State University of Malang assess the condition of the gully plug installations, their impact on sediment capture, erosion control, and soil stability. These insights help identify the most effective structure types, ensuring informed recommendations for future implementations.

The monitoring showed that series of gully plugs made sequentially following the channel from upstream to downstream are effective in retaining heavy water discharge and capturing sediment. On average, a 10-20 cm thick layer of sediment was found behind the installed gully plug structures, with the greatest accumulation of sediment occurring behind gully plugs with bamboo barricades filled with soil or grass and dense shrubs.
The other type of gully plug made of branches, was observed to have grown densely, providing a natural barrier to the heavy water discharge and sediment flowing along the channel.

Recommendation for replication
For replication, bamboo gully plugs and branch-made gully plugs are identified as the most effective, affordable, and easy-to-implement structures. These options are chosen based on their proven ability to capture sediment, ease of installation, support for vegetation growth, and the accessibility of materials, making them suitable for small-scale community implementation across diverse land uses.
On the other hand, gully plugs made from stone or even gabions tend to be more difficult for communities to implement without assistance from the government or third parties in procuring materials, but are structurally more robust and durable.