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Papers by Dhananjay Regmi

Research paper thumbnail of Glacier, Glacial Lake, and Ecological Response Dynamics of the Imja Glacier-Lake-Moraine System, Nepal

AGU Fall Meeting Abstracts, Dec 1, 2016

Research paper thumbnail of Tourism impacts on the mobility of local population in Sagarmatha (Mount Everest) National Park and Buffer Zone, Nepal

Research paper thumbnail of Trekking tourism and pack-animal transportation in Khumbu Himal, Nepal

Research paper thumbnail of Flood Assessment and Identification of Emergency Evacuation Routes in Seti River Basin, Nepal

Land, 2022

Sudden floods frequently occur in the Himalayas under changing climates. Rapid glacial melt has r... more Sudden floods frequently occur in the Himalayas under changing climates. Rapid glacial melt has resulted in the formation of glacial lakes and associated hazards. This research aimed to (1) identify flood-prone houses, (2) determine pedestrian emergency evacuation routes, and (3) analyze their relationships to socioeconomic status in the Seti River Basin. Detailed hazard maps were created using field survey results from unmanned aerial vehicle photogrammetry and the Hydrologic Engineering Center River Analysis System. Questionnaire, focus-group, and key-informant surveys helped identify the socioeconomic situation. Inundation maps revealed that most residents are exposed to future flooding hazards without proper evacuation routes. Highly impoverished and immigrant households were at the highest risk in terms of income inequality and migration rate (p < 0.001) and were located on the riverside. The locations of 455 laborers’ houses were significantly correlated with inundation haz...

Research paper thumbnail of A Geomorphic Study of Permafrost in the Nepal Himalaya

Permafrost in Nepal has received very little scientific attention, despite the fact that Nepal is... more Permafrost in Nepal has received very little scientific attention, despite the fact that Nepal is a country known for the Himalaya. Even the distribution of permafrost in Nepal has not been clarified yet. This book deals with the distribution of rock glaciers and permafrost in five high Himal areas of the Nepal Himalaya: Kangchenjunga, Khumbu, Langtang, Annapurna, and Sisne. Based on aerial photograph interpretation and intensive field surveys, the relationship between permafrost distribution and geomorphological arrangement were identified and described in this book.

Research paper thumbnail of Potential GLOF Hazards and Initiatives taken to minimize its Impacts on Downstream Communities and Infrastructures in Nepal Himalaya

Research paper thumbnail of Survey on damage in settlements along the Tamakoshi river in Dolakha, Nepal, caused by earthquakes in April/May 2015

The American Journal of Gastroenterology, 2016

Research paper thumbnail of Shrinkage of Nepal’s Second Largest Lake (Phewa Tal) Due to Watershed Degradation and Increased Sediment Influx

Remote Sensing, 2019

Phewa Lake is an environmental and socio-economic asset to Nepal and the city of Pokhara. However... more Phewa Lake is an environmental and socio-economic asset to Nepal and the city of Pokhara. However, the lake area has decreased in recent decades due to sediment influx. The rate of this decline and the areal evolution of Phewa Lake due to artificial damming and sedimentation is disputed in the literature due to the lack of a historical time series. In this paper, we present an analysis of the lake’s evolution from 1926 to 2018 and model the 50-year trajectory of shrinkage. The area of Phewa Lake expanded from 2.44 ± 1.02 km2 in 1926 to a maximum of 4.61 ± 0.07 km2 in 1961. However, the lake area change was poorly constrained prior to a 1957–1958 map. The contemporary lake area was 4.02 ± 0.07 km2 in April 2018, and expands seasonally by ~0.18 km2 due to the summer monsoon. We found no evidence to support a lake area of 10 km2 in 1956–1957, despite frequent reporting of this value in the literature. Based on the rate of areal decline and sediment influx, we estimate the lake will los...

Research paper thumbnail of A rockfall-induced glacial lake outburst flood, Upper Barun Valley, Nepal

Research paper thumbnail of Climate change and the global pattern of moraine-dammed glacial lake outburst floods

Research paper thumbnail of Evolution and Controls of Large Glacial Lakes in the Nepal Himalaya

Research paper thumbnail of Impact of Climate Change on Water Resources in View of Contribution of Runoff Components in Stream Flow: A Case Study from Langtang Basin, Nepal

Journal of Hydrology and Meteorology, 2016

Observation and model-based studies suggest substantial hydrological flow pattern changes in moun... more Observation and model-based studies suggest substantial hydrological flow pattern changes in mountain watershed where hydrology is dominated by cryospheric processes (IPCC 2007). The response of cryospheric processes to warming climate in mountain areas can be analysed by examining the responses in the seasonal and annual hydrologic regimes of rivers where snowmelt contributes significantly to the runoff. This study is carried out in Langtang basin, which aims to assess the impact of potential warming on snowmelt contribution and river discharge utilizes a Snowmelt Runoff Model (SRM), which is one of a very few models in the world today that requires remote sensing derived snow cover data as a model input. In this study, snow cover and hydrometric data were derived from Moderate Resolution Imaging Spectro-radiometer (MODIS) snow product and Snow and Glacier Hydrological Unit (SGHU) of Department of Hydrology and Meteorology, Government of Nepal. The model is calibrated for the year 2006 and validated in 2005. Different climatic scenarios are used (only change in temperature) to run the model in order to understand the impact of changing climate on runoff component and river discharge. In 2006, snow and glacier melt component contributes 35% in winter, 18% in summer and 19% annually in the stream flow. In this study, model predicts that snow and glacier melt contribution in stream flow will increase approximately at the rate of 2% in winter, 5% in summer and 4% in annual flow per 1°C temperature rise. Due to increase in snowmelt contribution, river discharge will also increase at the rate of 2% in winter, 6% in summer and 5% in annual flow under the projected temperature rise of 1°C.

Research paper thumbnail of Geomorphic and geologic controls of geohazards induced by Nepal's 2015 Gorkha earthquake

Science (New York, N.Y.), Jan 8, 2016

The Gorkha earthquake (magnitude 7.8) on 25 April 2015 and later aftershocks struck South Asia, k... more The Gorkha earthquake (magnitude 7.8) on 25 April 2015 and later aftershocks struck South Asia, killing ~9000 people and damaging a large region. Supported by a large campaign of responsive satellite data acquisitions over the earthquake disaster zone, our team undertook a satellite image survey of the earthquakes' induced geohazards in Nepal and China and an assessment of the geomorphic, tectonic, and lithologic controls on quake-induced landslides. Timely analysis and communication aided response and recovery and informed decision-makers. We mapped 4312 coseismic and postseismic landslides. We also surveyed 491 glacier lakes for earthquake damage but found only nine landslide-impacted lakes and no visible satellite evidence of outbursts. Landslide densities correlate with slope, peak ground acceleration, surface downdrop, and specific metamorphic lithologies and large plutonic intrusions.

Research paper thumbnail of Glacier Dynamics and Outburst Flood Potential from the Imja and Thulagi Glacier-Lake Systems (Nepal)

Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, ... more Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, i.e. most likely to cause death and destruction in case of a glacier lake outburst flood (GLOF). Imja Lake and the associated Imja and Lhoste-Shar glaciers have been intensively studied; Thulagi Glacier and its lake are much less studied. Collectively, we have undertaken a series of increasingly thorough bathymetric and land surveys and satellite remote sensing analyses of Imja Lake and its glacier setting. We are analyzing several expeditions' data to build a detailed assessment of the glacier and lake to better establish the dynamical evolution of the system and its future GLOF potential. Our most recent, most complete bathymetric survey of Imja Lake has revealed a much greater volume (75,200,000 cubic meters) and maximum depth (149.8 m) than found before. Our analysis suggests that not all possible Imja GLOF scenarios would result in devastation. Some moraine melt-through or down-...

Research paper thumbnail of Compounding Hazards Facing Nepalese Villages due to Glacial Lake Thulagi, Extreme Monsoons, and Landslides

Research paper thumbnail of The 2012 Seti River flood disaster and alpine cryospheric hazards facing Pokhara, Nepal

Research paper thumbnail of Rockfall in the Eastern Nepal Himalaya

The American Journal of Gastroenterology, 2003

Research paper thumbnail of aac8353 Science Supplementary Material FINAL-2

Research paper thumbnail of Rock Glacier Distribution and the Lower Limit of Discontinuous Mountain Permafrost in the Nepal Himalaya

Research paper thumbnail of Rockfall activity in the Kangchenjunga area, Nepal Himalaya

Permafrost and Periglacial Processes, 2009

Rockfall activity and related environmental factors (i.e. bedrock thermal regime and precipitatio... more Rockfall activity and related environmental factors (i.e. bedrock thermal regime and precipitation) were monitored through most of one year at elevations between 4600 m and 6800 m in the Kangchenjunga valley of the Nepal Himalaya to identify rockfall dynamics, estimate rockfall frequency for different aspects, and assess temporal and spatial variations in rockfall activity. Rockfall activity on north-facing slopes is mainly controlled by insolation relating to solar elevation and showed an abrupt increase in the pre-monsoon season. Rockfall activity on east-, west- and south-facing slopes is controlled by the duration and effectiveness of sunshine and accumulation of snow. The north-facing slope has a small diurnal range of rock surface temperatures and exhibits seasonal freeze-thaw, whereas the other aspects show frequent diurnal freeze-thaw. These differences result in seasonal rockfall activity on the north-facing slope and the infrequent release of large debris and year-round rockfall activity on the other aspects. Copyright © 2009 John Wiley & Sons, Ltd.

Research paper thumbnail of Glacier, Glacial Lake, and Ecological Response Dynamics of the Imja Glacier-Lake-Moraine System, Nepal

AGU Fall Meeting Abstracts, Dec 1, 2016

Research paper thumbnail of Tourism impacts on the mobility of local population in Sagarmatha (Mount Everest) National Park and Buffer Zone, Nepal

Research paper thumbnail of Trekking tourism and pack-animal transportation in Khumbu Himal, Nepal

Research paper thumbnail of Flood Assessment and Identification of Emergency Evacuation Routes in Seti River Basin, Nepal

Land, 2022

Sudden floods frequently occur in the Himalayas under changing climates. Rapid glacial melt has r... more Sudden floods frequently occur in the Himalayas under changing climates. Rapid glacial melt has resulted in the formation of glacial lakes and associated hazards. This research aimed to (1) identify flood-prone houses, (2) determine pedestrian emergency evacuation routes, and (3) analyze their relationships to socioeconomic status in the Seti River Basin. Detailed hazard maps were created using field survey results from unmanned aerial vehicle photogrammetry and the Hydrologic Engineering Center River Analysis System. Questionnaire, focus-group, and key-informant surveys helped identify the socioeconomic situation. Inundation maps revealed that most residents are exposed to future flooding hazards without proper evacuation routes. Highly impoverished and immigrant households were at the highest risk in terms of income inequality and migration rate (p < 0.001) and were located on the riverside. The locations of 455 laborers’ houses were significantly correlated with inundation haz...

Research paper thumbnail of A Geomorphic Study of Permafrost in the Nepal Himalaya

Permafrost in Nepal has received very little scientific attention, despite the fact that Nepal is... more Permafrost in Nepal has received very little scientific attention, despite the fact that Nepal is a country known for the Himalaya. Even the distribution of permafrost in Nepal has not been clarified yet. This book deals with the distribution of rock glaciers and permafrost in five high Himal areas of the Nepal Himalaya: Kangchenjunga, Khumbu, Langtang, Annapurna, and Sisne. Based on aerial photograph interpretation and intensive field surveys, the relationship between permafrost distribution and geomorphological arrangement were identified and described in this book.

Research paper thumbnail of Potential GLOF Hazards and Initiatives taken to minimize its Impacts on Downstream Communities and Infrastructures in Nepal Himalaya

Research paper thumbnail of Survey on damage in settlements along the Tamakoshi river in Dolakha, Nepal, caused by earthquakes in April/May 2015

The American Journal of Gastroenterology, 2016

Research paper thumbnail of Shrinkage of Nepal’s Second Largest Lake (Phewa Tal) Due to Watershed Degradation and Increased Sediment Influx

Remote Sensing, 2019

Phewa Lake is an environmental and socio-economic asset to Nepal and the city of Pokhara. However... more Phewa Lake is an environmental and socio-economic asset to Nepal and the city of Pokhara. However, the lake area has decreased in recent decades due to sediment influx. The rate of this decline and the areal evolution of Phewa Lake due to artificial damming and sedimentation is disputed in the literature due to the lack of a historical time series. In this paper, we present an analysis of the lake’s evolution from 1926 to 2018 and model the 50-year trajectory of shrinkage. The area of Phewa Lake expanded from 2.44 ± 1.02 km2 in 1926 to a maximum of 4.61 ± 0.07 km2 in 1961. However, the lake area change was poorly constrained prior to a 1957–1958 map. The contemporary lake area was 4.02 ± 0.07 km2 in April 2018, and expands seasonally by ~0.18 km2 due to the summer monsoon. We found no evidence to support a lake area of 10 km2 in 1956–1957, despite frequent reporting of this value in the literature. Based on the rate of areal decline and sediment influx, we estimate the lake will los...

Research paper thumbnail of A rockfall-induced glacial lake outburst flood, Upper Barun Valley, Nepal

Research paper thumbnail of Climate change and the global pattern of moraine-dammed glacial lake outburst floods

Research paper thumbnail of Evolution and Controls of Large Glacial Lakes in the Nepal Himalaya

Research paper thumbnail of Impact of Climate Change on Water Resources in View of Contribution of Runoff Components in Stream Flow: A Case Study from Langtang Basin, Nepal

Journal of Hydrology and Meteorology, 2016

Observation and model-based studies suggest substantial hydrological flow pattern changes in moun... more Observation and model-based studies suggest substantial hydrological flow pattern changes in mountain watershed where hydrology is dominated by cryospheric processes (IPCC 2007). The response of cryospheric processes to warming climate in mountain areas can be analysed by examining the responses in the seasonal and annual hydrologic regimes of rivers where snowmelt contributes significantly to the runoff. This study is carried out in Langtang basin, which aims to assess the impact of potential warming on snowmelt contribution and river discharge utilizes a Snowmelt Runoff Model (SRM), which is one of a very few models in the world today that requires remote sensing derived snow cover data as a model input. In this study, snow cover and hydrometric data were derived from Moderate Resolution Imaging Spectro-radiometer (MODIS) snow product and Snow and Glacier Hydrological Unit (SGHU) of Department of Hydrology and Meteorology, Government of Nepal. The model is calibrated for the year 2006 and validated in 2005. Different climatic scenarios are used (only change in temperature) to run the model in order to understand the impact of changing climate on runoff component and river discharge. In 2006, snow and glacier melt component contributes 35% in winter, 18% in summer and 19% annually in the stream flow. In this study, model predicts that snow and glacier melt contribution in stream flow will increase approximately at the rate of 2% in winter, 5% in summer and 4% in annual flow per 1°C temperature rise. Due to increase in snowmelt contribution, river discharge will also increase at the rate of 2% in winter, 6% in summer and 5% in annual flow under the projected temperature rise of 1°C.

Research paper thumbnail of Geomorphic and geologic controls of geohazards induced by Nepal's 2015 Gorkha earthquake

Science (New York, N.Y.), Jan 8, 2016

The Gorkha earthquake (magnitude 7.8) on 25 April 2015 and later aftershocks struck South Asia, k... more The Gorkha earthquake (magnitude 7.8) on 25 April 2015 and later aftershocks struck South Asia, killing ~9000 people and damaging a large region. Supported by a large campaign of responsive satellite data acquisitions over the earthquake disaster zone, our team undertook a satellite image survey of the earthquakes' induced geohazards in Nepal and China and an assessment of the geomorphic, tectonic, and lithologic controls on quake-induced landslides. Timely analysis and communication aided response and recovery and informed decision-makers. We mapped 4312 coseismic and postseismic landslides. We also surveyed 491 glacier lakes for earthquake damage but found only nine landslide-impacted lakes and no visible satellite evidence of outbursts. Landslide densities correlate with slope, peak ground acceleration, surface downdrop, and specific metamorphic lithologies and large plutonic intrusions.

Research paper thumbnail of Glacier Dynamics and Outburst Flood Potential from the Imja and Thulagi Glacier-Lake Systems (Nepal)

Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, ... more Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, i.e. most likely to cause death and destruction in case of a glacier lake outburst flood (GLOF). Imja Lake and the associated Imja and Lhoste-Shar glaciers have been intensively studied; Thulagi Glacier and its lake are much less studied. Collectively, we have undertaken a series of increasingly thorough bathymetric and land surveys and satellite remote sensing analyses of Imja Lake and its glacier setting. We are analyzing several expeditions' data to build a detailed assessment of the glacier and lake to better establish the dynamical evolution of the system and its future GLOF potential. Our most recent, most complete bathymetric survey of Imja Lake has revealed a much greater volume (75,200,000 cubic meters) and maximum depth (149.8 m) than found before. Our analysis suggests that not all possible Imja GLOF scenarios would result in devastation. Some moraine melt-through or down-...

Research paper thumbnail of Compounding Hazards Facing Nepalese Villages due to Glacial Lake Thulagi, Extreme Monsoons, and Landslides

Research paper thumbnail of The 2012 Seti River flood disaster and alpine cryospheric hazards facing Pokhara, Nepal

Research paper thumbnail of Rockfall in the Eastern Nepal Himalaya

The American Journal of Gastroenterology, 2003

Research paper thumbnail of aac8353 Science Supplementary Material FINAL-2

Research paper thumbnail of Rock Glacier Distribution and the Lower Limit of Discontinuous Mountain Permafrost in the Nepal Himalaya

Research paper thumbnail of Rockfall activity in the Kangchenjunga area, Nepal Himalaya

Permafrost and Periglacial Processes, 2009

Rockfall activity and related environmental factors (i.e. bedrock thermal regime and precipitatio... more Rockfall activity and related environmental factors (i.e. bedrock thermal regime and precipitation) were monitored through most of one year at elevations between 4600 m and 6800 m in the Kangchenjunga valley of the Nepal Himalaya to identify rockfall dynamics, estimate rockfall frequency for different aspects, and assess temporal and spatial variations in rockfall activity. Rockfall activity on north-facing slopes is mainly controlled by insolation relating to solar elevation and showed an abrupt increase in the pre-monsoon season. Rockfall activity on east-, west- and south-facing slopes is controlled by the duration and effectiveness of sunshine and accumulation of snow. The north-facing slope has a small diurnal range of rock surface temperatures and exhibits seasonal freeze-thaw, whereas the other aspects show frequent diurnal freeze-thaw. These differences result in seasonal rockfall activity on the north-facing slope and the infrequent release of large debris and year-round rockfall activity on the other aspects. Copyright © 2009 John Wiley & Sons, Ltd.