Cyclone Arnab’s remnants raise landslide risk on Nepal’s main highways

Nepal’s authorities have identified several highway sections as vulnerable to landslides, rockfalls, flooding and erosion. The warning focuses on the Narayani, Bagmati and Koshi river basins and nearby areas. These risks matter because the routes connect communities and carry people and essential supplies.

The Narayanghat-Muglin highway is specifically highlighted because it runs alongside the Trishuli and Narayani rivers. Vulnerable sections of the Koshi and Siddhartha highways are also flagged. The Kanti and Araniko highways, along with roads linked to the Bagmati basin, are included as well.

Other routes with past landslides or close to rivers are considered vulnerable. The assessment identifies possible hazards, not confirmed closures. Authorities have urged people to avoid highway travel during rain unless necessary and to check traffic police and road authority updates before leaving.

A landslide is the movement of soil, rocks or broken earth down a slope. It can happen suddenly and may bury or damage roads. In Nepal, the danger is especially serious on steep, hilly terrain, where highways often pass beneath slopes or beside rivers.

Heavy rain adds water to the ground. The soil can become heavier and less tightly held together. Water also raises pressure between soil particles, reducing friction that helps keep a slope stable. Once the resisting strength falls below the force pulling material downhill, the slope can collapse.

The article warns that the cyclone’s remnants may bring more rain to Nepal over the next few days. It identifies hilly terrain and steep slopes as particularly vulnerable. Landslides and falling rocks could block highways, disrupt transport and delay essential supplies, even though no closures were confirmed.

Cyclone Arnab crossed India’s Andhra Pradesh and Yanam coasts on Wednesday with sustained winds of 125-135 kph. Gusts reached up to 150 kph. Those figures describe the storm at landfall and show that it arrived as a powerful system.

After crossing the coast, Arnab weakened as it moved inland. The article describes its remaining system as a deep depression. A deep depression is weaker than the original cyclone, so Nepal was not expected to experience similarly strong winds. However, weakening did not remove the rainfall threat.

The article does not provide a specific wind speed for Arnab near Nepal. It says rain and snowfall remained possible as the residual system moved inland. Authorities therefore focused on landslides, floods, travel disruption and mountain weather rather than cyclone-strength winds.

A cyclone can continue affecting places far from its landfall after losing its strongest winds. Its remaining circulation and weather system may move inland, carrying moist air and producing clouds and rain. This is why a storm that struck India’s coast can still influence Nepal.

Arnab made landfall on India’s Andhra Pradesh coast, then weakened into a deep depression as it moved inland. The weakened system was still expected to bring rainfall to parts of Nepal. Rainfall, rather than cyclone-strength wind, became the main concern for roads, slopes, rivers and mountain travel.

Authorities warned that the residual system could raise landslide and flood risks over the next few days. Rain and snowfall also remained possible. Trekkers, mountaineers, tourists, airports, district administrations and security agencies were told to monitor official forecasts and prepare for weather-related disruption.

Roads beside rivers face danger because heavy rain increases the volume and speed of water. Rivers can rise over their banks, flood the road or erode the ground supporting it. This can weaken road edges, damage foundations and leave transport routes unsafe.

Smaller streams can also become powerful during intense rainfall. Water rushing through roadside culverts may exceed their capacity or scour nearby soil. The article specifically warns that heavy flows in smaller streams and through culverts could damage roads. River-adjacent routes therefore face both flooding and erosion.

These risks are important on highways such as Narayanghat-Muglin, which follows the Trishuli and Narayani rivers. Authorities have flagged other routes near rivers or with a history of landslides. They warn that damage could block highways and disrupt essential supply movements, although no closures were confirmed.

Landslides and floods can make highways impassable or unsafe. A blocked road interrupts journeys by residents, vehicles and emergency workers. Because major highways carry goods as well as people, closures can also delay food, fuel, medicine and other essential supplies.

The article identifies several possible ways this could happen. A landslide may cover the road with soil and rocks. Floodwater may cross the carriageway, while river erosion or rushing water through a culvert may damage the road itself. Falling rocks can create another sudden obstruction, especially along steep slopes.

Authorities have warned that transport and essential-supply movement could be disrupted over the next few days. However, the notice describes potential hazards and does not report confirmed road closures. People are advised to avoid highway travel during rainfall unless necessary and to check official updates before setting out.

Forecasts reduce danger by showing when rain, snowfall or other hazardous weather may affect roads and mountains. Traffic restrictions or advice can keep people away from exposed routes at the worst time. The authorities urged the public to avoid unnecessary highway travel during rainfall and follow official notices rather than rumours.

Road inspections help identify damage, flooding, erosion or blocked sections before more vehicles enter. Traffic police and road authorities can then provide current route information. Emergency preparations also matter. Nepal’s Civil Aviation Authority ordered reviews of flight plans, runways, air traffic systems, communications and power systems, while districts and security agencies were asked to assess local risks.

These measures cannot stop rain or landslides, but they can reduce exposure and improve response. Travellers, trekkers and climbing teams should check updated forecasts before leaving. Continued official monitoring is important because the weakened storm may still bring rain and snowfall.