Speaker
Description
The Himalayan mountains of Nepal comprise the highest elevations, deepest river gorges, and greatest topographic relief on Earth. Contributing to this extraordinary landscape are some of the world’s highest rock uplift rates and largest river systems. This research focuses on investigating the vertical incision of the Kali Gandaki River in Central Nepal to elucidate the spatial and temporal relationship between rock uplift and river erosion of large mountain belts. Recent fieldwork and remote sensing observations have revealed abandoned, uplifted, and incised river gravels perched high above the modern river, which spatially coincides with high rates of vertical uplift and previously identified major tectonic structures. Samples collected from these stranded gravels for geochronology will provide age estimates of these perched river deposits and therefore rates of vertical incision by the Kali Gandaki over the geologic past, shedding light on interactions between tectonic growth of the Himalayas and surface processes such as river dynamics.
Furthermore, we address the challenges posed by climate change and monsoon shifts in Himalayan rain shadow zones that impact the livelihoods of mountain communities. On August 13, 2023, record-breaking rainfall triggered a catastrophic debris flow in the Jhong Khola basin, a tributary to the Kali Gandaki River. This extreme event destroyed 29 houses, displacing over 150 individuals, and resulted in an estimated property loss of $7 million. Such events, including those from tributaries like the Jhong Khola, have profound impacts on river dynamics and the morphological evolution of major river systems. In Fall 2023, we conducted fieldwork at the Jhong Khola-Kali Gandaki confluence involving drone-based structure-from-motion (SFM) surveys to generate high-resolution digital elevation models (DEMs) of the areas most impacted by the extreme August 2023 event. By leveraging drone-based SFM data, satellite imagery, and local insights, we aim to quantify the recent event and identify potential causes. Additionally, we aim to categorize the impacts rapid sediment flux events such as this have on river dynamics. This research contributes valuable insights into the intricate interplay between tectonic processes, surface dynamics, and extreme events of the Himalayas, providing critical knowledge for understanding and mitigating the impacts of natural hazards on mountain communities.
