"While the immediate consequences of a major disaster are often the most visible, the ensuing deterioration in population health can be equally consequential. The initial burden of traumatic injury may be followed by a complex secondary health crisis. This is often driven by displacement of the local populace, disrupted healthcare infrastructure, overcrowding, compromised sanitation, limited access to clean water and interruption of essential medical services.

Under these conditions, already vulnerable communities face an increased risk of wound complications, respiratory and communicable disease, dehydration, exacerbation of chronic illness and delayed treatment of otherwise manageable conditions. Critically, these effects do not necessarily resolve as the immediate emergency subsides. Rather, the health consequences of a catastrophic event can persist—and in some circumstances intensify—well beyond the initial disaster.

The situation in Nepal therefore requires us to look beyond the immediate casualty figures. The true health burden of a disaster is measured not only by what occurs during the event itself, but also by the capacity of the affected health system and humanitarian response to protect communities in the days and weeks that follow.

That being said, with the remaining Australians still missing, there is still hope. During the Türkiye earthquake crisis, we were pulling civilians out of rubble alive close to the two-week mark. As a collective, we need to rally behind organisations currently on the ground, support local efforts and maintain a posture of hope for more survivors."

"The rescue operation remains the immediate priority, particularly for those still missing or trapped. The work of Nepalese rescue personnel, local communities and international specialist teams deserves enormous recognition. The support Nepal is receiving from international partners, through specialist expertise, equipment and humanitarian assistance, is greatly appreciated.

At the same time, we need to start thinking about recovery. One immediate challenge is reconnecting communities and restoring essential lifeline services where roads, bridges, electricity and communications have been disrupted. Rasuwa, Nuwakot and Dhading alone are home to more than 600,000 people who depend on these systems for food, fuel, healthcare, education, internet and everyday life. Furke Khola bridge in Dhading is one example. Its collapse disrupted the main road connection between Dhading Besi and eight local governments, an area home to nearly 180,000 people.

Temporary roads and bridges will be essential to restore access quickly. Bailey bridges can be very useful where the span and site conditions are suitable, while larger crossings will need other solutions. But temporary solutions must remain temporary. When permanent infrastructure is rebuilt, we should not simply replace what was there before. We need to understand why it was vulnerable and design for the floods, landslides, earthquakes and other hazards it may face during its lifetime.

The rescue operation also raises an important question. When people are trapped in tunnels, bridges are gone, communications fail and communities become inaccessible, do we have the specialist people, equipment and technology ready to respond immediately? International assistance will always be important, but these are not once-in-a-million-year events for Nepal. We face disasters repeatedly. We need to build more of this specialist capability within the country rather than trying to assemble it after a disaster has happened. Every second matters, and we cannot afford to wait for specialist people and equipment to arrive from overseas when we already know we may need them.

For me, that is the main lesson as we move towards recovery. We have to rebuild, but we should come out of every major disaster better prepared for the next one."

"The Bhote Koshi flood was not due to rain; instead, it was due to glacial collapse.

Two things failed that day, and only one of them was hydrological.

The first was our mental model of what a flood looks like. People in these valleys know monsoon floods with little living memory of ice-rock avalanches and cascading outburst floods of this kind. So, when the sky is clear and someone says a major flood is coming, it is not surprising that people hesitate.

The second failure is harder for my own field to admit. Hydrology's instinct, mine included, is to ask for more observations, better satellite products, and better models. Even my own research is about improving rainfall information for ungauged catchments. Here, that instinct is rarely applicable as the trigger was not rainfall. No improved rainfall product would have seen this flood coming.

That changes how we should think about these events.

Perhaps these floods are not a matter of forecasting accuracy; in fact, they are closer to near-field hazards such as a local tsunami: the source is close, the travel time is short, and by the time the danger is confidently detected, there may be very little time left to respond. For such hazards, preparedness cannot depend entirely on the promise of a timely warning. Himalayan valleys increasingly need the same logic.

As the Himalaya warms, these events are expected to increase. The uncomfortable lesson from Bhote Koshi is therefore not that we need a better forecast, but that some floods may never offer the warning time, and that important decisions must be made long before the water starts moving.”

"We have a reasonable understanding about what triggers landslides like the devastating one in Nepal late last month.

Even though the landslide was a rapid and catastrophic event, it was likely decades or more in the making. Cold water infiltrates the rocks in mountains and freeze thaw cycles shatter the rock, making it unstable. In summer part of the glacier melts, infiltrating and lubricating the fractures in the rock which eventually fails. Sometimes such failures can be captured in progress as fractures in the rock and ice grow over time before they catastrophically collapse.

However, there are two questions that are left unanswered: the extent to which warming of alpine glaciers such as this due to global climate change have contributed; and whether monitoring of the glaciers, beyond satellite observations, could have provided an early warning to alert residents downstream. India has already announced plans to step up monitoring in response to the recent disaster, which is encouraging to hear."

"The landslide and flood that hit Nepal last week was remarkable for the volume of water that was involved, and the height of the surge that resulted. While the cause of the landslide appears to be related to the collapse of a glacier, the source of the water is less clear. It could have come from melting ice, meltwater trapped within, beneath or on top of the ice, lakes dammed by previous landslides, and water trapped within the sediment dislodged by the landslide.

Similar, less catastrophic, but nonetheless devastating floods occurred on the Chinese side of the border in July last year, caused by the sudden escape of meltwater trapped in lakes on the tops of glaciers. The narrow valley in which the floods occurred focused the water, increasing the height of the surge.

Another remarkable aspect was how rapidly events unfolded in Nepal - there was only about seven minutes between the earthquake caused by the glacier collapse and the wave engulfing the border crossing at Gyirong Port, meaning that there was little time to provide warnings in situations such as this."

"The recent disaster in Nepal and Tibet demonstrates how multiple hazards can interact with cascading and compounding impacts. Considered essentially a Glacial Lake Outburst Flood (GLOP), a massive broken chunk of ice from the melting glacier in the Himalayas rushed downstream, gathering together an avalanche of debris, mud and rocks to form a gigantic flash flood with devastating effects on the settlements in its path.

Two main lessons – 1. Hazards should not be viewed in isolation, the combined impacts of multiple hazards should be expected and prepared for; and 2. The underlying culprit is climate change – ongoing and insidious - which was the key generating factor, pointing to our need to understand how to prepare, mitigate and build resilience for a changed and changing climate and environment.

A key issue that rose in prominence in Nepal after the 2015 Gorkha earthquakes is that of building codes, with a review and improvement of codes that followed. Some of the areas in Nepal affected by the recent disaster were also impacted in the 2015 earthquakes, and buildings supposedly rebuilt following the codes were nevertheless devastated by a different form of hazards, a combination thereof.

The essential lesson here is, again, to prepare for a multi-hazard situation with codes that offer wider protection based on a thorough local risk assessment. However, implementation and compliance to such codes remain sketchy, as our research on building codes and disaster resilience in Nepal and Bangladesh indicated (see our peer-reviewed paper and also a dissemination video on the research).

Recovery will be a protracted and difficult process, especially because the region consists of mountainous terrain that will hinder international assistance. Although a large amount of aid, almost USD 5 million has been raised, the huge amount of international assistance that will be needed to address the highly extensive devastation will face uncertainty in the current global economic downturn due to the war in the Middle East and Ukraine. The key issue to hope for is that the recovery follows the 'building back better' approach so that future risk is reduced."

"As we approach a week from the devastating floods in Nepal, the reason for the disaster may have become clearer, but the task facing rescuers and the grief upon families endures.

I have been conferring with colleagues globally about the cause of the disaster, but more importantly I have been conferring about what we the international community might do, to enable better warning of such events in the future."

Adrian also provided commentary in the immediate aftermath of the disaster last week.