A narrative of flood fury and resilience

Itahari, a fast-developing town in the Koshi Province of Nepal, is locked in a recurring battle with floods. Its location seals its fate—hemmed in by the Chure hills on one side and rain-fed rivers and streams on the other, the town is precariously perched on a path of raging waters. Itahari's story is one of nature's delicate balance being tampered with. Once a verdant expanse with the Charkose Jhaadi (CKJ) forest acting as a natural sponge, absorbing and channeling rainwater, the landscape has undergone a drastic transformation. A large part of the forest has been cleared for settlements and infrastructure, erasing the very buffers. These encroachments have choked the natural flow paths of streams and creeks, turning them into ticking time bombs waiting to burst at the seams of a heavy downpour.

Gushing streams and creeks

The culprit behind Itahari’s woes is the rapid flow—rain hammering the Chure hills creates flash floods. These surges of water race down the denuded slopes, overwhelming the already-burdened streams like Shera Khola, Tyangra Khola, Budhi Khola. Kheti Khola and many others. The peculiar topography of the area further amplifies the problem. The land slopes channelize the floodwaters in a southwesterly direction, inundating Itahari in its path. Itahari’s woes are compounded by its complex river system. The CKJ forest once housed a web of streams and creeks; today, many are buried, diverted, or even closed, their paths lost under the urban sprawl. This tangled web makes it incredibly difficult to predict and manage floodwaters.

Shera Khola, a vital artery carrying water from the hills, splits into two upon entering the CKJ forest. The main branch, Shera, and its distributary retaining the name Shera as well, snakes through the forest. It eventually merges with Tyangra Khola, originating from the rainwater reservoir, Taltalaiya, located within the CKJ forest. The two streams merge just before entering Itahari, their combined might creating a formidable challenge. Tyangra's journey through Itahari is fraught with peril. Years of human intervention have taken their toll. The stream is heavily channelized, encroached upon, and choked with sediment, debris and waste. Culverts meant to regulate the flow are often inadequate, overwhelmed by the sheer volume of water. As Tyangra snakes its way through the town, it cuts across the East-West highway and the North-South highway several times, acting as barriers. The narrow and clogged culverts under these highways become bottlenecks, further aggravating the flooding. Shera Khola merges with Budhi Khola further downstream, diverting some of the floodwaters away from Itahari. This diversion might lessen the burden on some parts of the town, but it comes at a cost. The increased water flow in Budhi Khola increases the risk for the eastern part of the town as well as downstream areas including the capital of the province—Biratnagar.

Itahari’s woes are not limited to Shera and Tyangra. Smaller streams like Kheti Khola, Hakraha Khola, Sukumari Khola and many others, all receiving water from the CKJ forest, create problems in the central and western parts of the municipality. Seuti Khola, another major stream, flows westward, seemingly separate from the others. However, its proximity to Shera Khola where it begins its journey in the CKJ forest suggests a possible exchange of flows. The East-West highway, a vital transportation link, has unwittingly become a flood risk amplifier. Built on higher ground, it severs the natural flow paths of the streams. Culverts along this highway are frequently clogged, causing water to flood the areas on the north side. Further downstream, the Sunsari-Morang irrigation canal also presents a hurdle with narrow and clogged culverts and flow passages.

Learning from losses

Itahari’s recent encounters with floods in 2017 and 2021 offer valuable insights into the town's vulnerabilities. The 2017 flood highlighted the dangers of river morphological changes in Budhi Khola, where erosion and overflowing riverbanks caused inundation in the eastern part of the town. Encroachment on the river corridor further exacerbated the problem. This flood also exposed the shortcomings of the suspension bridge, whose blockage led to upstream flooding and a disastrous burst downstream. The 2021 flood painted a different picture. Here, the culprit was Shera Khola, overflowing its banks and spilling into Tyangra Khola. This surge of water, coupled with overland flow through the already encroached CKJ forest, caused problems in the western part of Itahari. The heavily built-up nature of Tyangra Khola and other streams, reduced to a narrow, choked drainage ditch, further amplified the issue.

The way forward

The road to a flood-resilient Itahari and surrounding areas lies in adopting a holistic and integrated approach. Here are some key takeaways for moving forward:

Revitalizing the forest: The degraded CKJ forest is a vital piece of the puzzle. Restoration efforts should focus on creating new water bodies and wetlands, managing fluvial deposits and debris, and replanting native vegetation. This will enhance the forest's capacity to store and regulate floodwater. Regular assessments to identify strategic depressions for temporary water storage can further improve flood control while maintaining ecological balance. This would not only reduce flood risk and improve the biodiversity of the CKJ but also replenish the groundwater supply favorable for Dharan municipality.

Managing major streams: Effective management of streams originating from the Chure hills is essential. Focusing on the major streams—Budhi Khola, Shera Khola and Seuti Khola—a riverfront development plan incorporating nature-friendly solutions can offer a multi-pronged approach to flood mitigation and create lively public spaces. Optimizing the flow distribution between Shera Khola, Budhi Khola and Seuti Khola through the CKJ, seizing the opportunity provided by nature, to minimize flood risk in Itahari and other neighboring municipalities.  

Ensuring a smooth flow: Restoring the whispers of forgotten streams, Itahari can embrace a future where water is both managed and celebrated. Upgrading drainage and exploring natural solutions like sustainable urban systems is key. But a more intriguing vision lies in creating a network of canals, weaving life back into existing, neglected waterways. Imagine a network of canals snaking through Itahari, interconnecting all the existing, albeit encroached, creeks and streams. These canals, strategically designed and integrated into the urban fabric, could become lifelines during floods. Floodwater overflowing from streams like Tyangra Khola, Kheti Khola, and others could be efficiently channeled. Drawing inspiration from water management strategies in some European countries like the Netherlands, this approach proposes a network of interconnected canals. Strategically placed pumping stations, powered by renewable energy sources, would regulate water flow during both floods and low-flow periods with designated retention areas. This stream network wouldn’t just be functional; it could be a thing of beauty. The canals, lined with native vegetation and landscaped walkways, could become a defining feature of Itahari. Encroached areas along the streams could be transformed into vibrant public spaces with cafes, recreational areas, and green walkways. This approach eliminates the need for demolishing houses, fostering community buy-in and creating a win-win situation.

Early warning systems: These systems are the lifeline for disaster preparedness and management. Effective flood and sediment management hinges on a robust network of monitoring, forecasting and early warning systems.

For a sustainable future

Implementing these strategies requires careful consideration of their technical, economic, social and environmental impacts and feasibilities. Challenges like limited space due to rapid urbanization and competition for land use make proposed strategies difficult. Integrating new measures with existing infrastructure and securing funding require innovative approaches. Public perception also plays a role, as some may have misconceptions about the proposed measures, fearing land loss or disruption. Overcoming these hurdles involves clear communication with stakeholders, and fostering community engagement to address concerns and highlight the long-term benefits.  By working together and embracing a sustainable approach, Itahari can transform itself from a flood-prone town to a thriving, resilient city.

The author is a specialist in river basin management and water infrastructure, currently employed at the international organization Royal HaskoningDHV, headquartered in The Netherlands. With over 28 years of professional experience, he actively contributes to river management projects globally

[email protected]