Mountains in transition: reading water to anticipate risk

Landslides, glaciers, and rivers in the northern sector of Los Glaciares National Park

In high-mountain landscapes, we often think of risk as something sudden: a slope that gives way, a rockfall, a road cut off. Yet behind every landslide there is a long story, written slowly by water, ice, and gravity.

In the northern sector of Los Glaciares National Park, in southern Patagonia, that story is accelerating. In 2024, the Andean Geomatics Laboratory of IANIGLA analyzed in the journal Quaternary International how glacier retreat and the reorganization of the hydrological system are conditioning landslide susceptibility. What the study shows is clear: where water has been, passed through, or continues to circulate, the terrain today is more fragile.

A territory shaped by water and ice

The study area is located in the northern sector of Los Glaciares National Park, a region dominated by the direct influence of the Southern Patagonian Ice Field. Rivers such as the Río de las Vueltas originate here, proglacial lakes such as Torre and del Desierto develop, and extensive moraine deposits are found.

The authors describe this landscape as highly dynamic:

“The region is characterized by a complex interaction between current glaciers, retreating glaciers, proglacial rivers, and moraine deposits.”

In El Chaltén, we are not dealing with a stable system, but with a territory that is constantly reorganizing as the ice retreats and water seeks new pathways.

Glacier retreat as a starting point

One of the conceptual pillars of the study is that glaciers are not only water reservoirs; they are also structures that support the landscape. When a glacier retreats, it leaves behind steep slopes, loose sediments, and unconsolidated surfaces.

The paper states this directly:

“Glacier retreat produces over-steepened slopes and exposes unconsolidated materials, increasing the predisposition to landslides.”

This process creates what we might call unstable legacies: places that do not fail immediately but are primed to do so when a trigger acts, such as intense rainfall, flooding, or increased seasonal melt.

The silent role of water

Although the study does not analyze extreme precipitation events, water is present in almost all the factors that increase landslide susceptibility.

The most vulnerable zones coincide with:

• internal and lateral moraines

• glaciofluvial deposits

• poorly consolidated Quaternary materials

• transition zones between ice, water, and soil

Regarding these materials, the authors note:

“The dominant Quaternary deposits are composed of blocks, gravels, and sands that are poorly consolidated.”

From a hydrological perspective, this is fundamental. These are materials that absorb and transmit water easily, reducing internal friction and favoring movement on slopes. Water does not always trigger the landslide, but it prepares the ground.

Detailed analysis (1)

In addition, the study shows that, in certain cases, vegetation can increase instability by adding weight to the slope and facilitating deep water infiltration, which raises internal soil pressure. This is compounded by the glacial legacy: slopes steeper than 30° exert especially high stress on Quaternary glacial sediments, which are loose and poorly consolidated materials. Slope aspect also matters: differences in solar radiation generate thermal cycles that weaken the material, and in the study area, south-facing slopes show a greater association with landslides, probably due to the presence of unstable moraines. Finally, terrain shape plays a key role: concave slopes act as zones of water and sediment accumulation, making the soil more susceptible to movement. Together, these factors reinforce a central idea of the study: water not only erodes from the surface but also destabilizes the landscape from within.

A revealing contrast: when the river stabilizes

One of the most interesting contributions of the study is showing that not all proximity to water implies greater risk. In the valley floor of the Río de las Vueltas, for example, susceptibility is low.

“In the central area of the Río Las Vueltas valley, conditions are not favorable for landslides, since it is a floodplain with gentle slopes.”

Here, water plays a different role: it transports fine sediments, reduces slopes, and redistributes energy. From this perspective, the problem in terms of risk management lies in how water circulates and what materials it flows through.

How landslide susceptibility is studied

To analyze these dynamics, the study uses a statistical approach known as the Frequency Ratio Model (FRM). This is important to understand, because it is a widely used tool in watershed and mountain studies.

In simple terms, the method answers one question:Where did landslides occur in the past, and what conditions did those places have?

The process includes:

• inventorying known landslides

• defining conditioning factors

• statistically evaluating how strongly those factors are associated with landslides

• generating a susceptibility map

In the study, the factors considered were slope, elevation, aspect, lithology, geomorphology, land cover, and distance to structural elements. Geomorphology—the forms of the terrain—proved to be the most influential factor.

Results: a map that anticipates

The model allowed the territory to be classified into different susceptibility categories. Areas of high and very high susceptibility are concentrated in:

• recently deglaciated areas

• internal moraines

• steep slopes with loose materials

The quality of the model was statistically evaluated:

“The AUC value obtained was greater than 0.8, indicating good predictive performance of the model.”

This means that the map is not merely descriptive; it has real capacity to anticipate risk zones, which is key for territorial management and planning.

“Under climate change scenarios, the results of this work can help reduce vulnerability and mitigate risks.”

As glaciers continue to retreat, the exposed surface area will increase, water flows will change, and stability conditions will be modified. In this sense, landslides are not anomalies: they are an expression of system readjustment.

Measuring is also a form of justice

Mountain regions with glaciers are often remote and poorly instrumented, yet they are crucial for water provision. Mapping risks, understanding processes, and generating data is a way of not leaving these territories off the map.

Landslides are not just geological accidents. They are the visible consequence of a territory where water has changed its place. Understanding them requires viewing the landscape as a living system, where rivers, glaciers, and slopes are in constant dialogue.

The management of emerging climate risks is a necessity for all mountain ecosystems. Join the HidroClim network to help collect data useful for climate risk management in El Chaltén!