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The colossal Himalayan risks – Himachal Floods of 2023. Are we prepared?

The Indian Himalayan region (IHR) is spread across 13 states/union territories, and nearly 50 million people reside there. IHR stretches about 2,400 kilometres across the northern border of India, covering an area of approximately 500,000 km2. In IHR, natural hazards such as landslides, avalanches, cloudbursts, floods and flashfloods are common, especially during the June-to-September monsoon season, and they often become disastrous for those living on the Himalaya’s fringes. The disastrous events are becoming more frequent as global warming melts the Himalayan glaciers. According to the Global Climate Risk Index Report 2019, India is the 14th most vulnerable country in the world to climate extreme events. India suffered an economic loss of USD 79.5 billion due to climate-related disasters in the last 20 years, according to the UN report titled Economic Losses, Poverty and Disasters (1998-2017). The economic losses due to disasters in the state of Himachal were nearly Rs 8,000 crore between 2017 and 2022 (Himachal Pradesh State Disaster Management Authority). The annual losses from climate-related disasters are steadily increasing everywhere. This shows that more people and infrastructure are exposed to natural hazards, leading to increased climate risk. The 2,500 km-long Himalayan plate boundary is also intensely prone to powerful earthquakes. Scientists fear a great earthquake of 8.5 magnitude or higher in the region. Such a predicted seismic event will create cascading disasters and have a catastrophic effect on the area. Are we prepared for such extreme events?

Although the population density is not very high, the states in IHR attract a vast number of tourists. The rapid urbanization and tourism activities are leading to increased human interference in the fragile hilly areas, especially in the Himachal and Uttarakhand regions. There has been an unprecedented growth in tourist arrivals in the Indian Himalayan states in the past few years. It is estimated that by 2025, 240 million tourists will visit yearly; it was 100 million in 2014, see Figure 1 (NITI Aayog, 2018). The extensive development and tourism activities will affect the soil strength and cause soil loosening. During extreme rainfall events, the soil can easily crack, trigger landslides and lead to road blockages. The impetus to urbanization and unparalleled tourism is bound to bring rapid regional climate variations and transform natural disasters into man-made or anthropogenic disasters.

Figure 1 Tourist arrival forecast in the IHR states by 2025 (Source: NITI Aayog, 2018)

Hazard scenario in Himachal

Floods in Himachal have been a damaging phenomenon, and one of the earliest records of destructive floods dates back to 1894 in River Beas. There were flash flood events in Beas in the 1980s, and the flood situation worsened from 1992 to 1996, see Figure 2. Extreme rainfall during the monsoon season is the primary cause of floods in the state; however, cloudbursts and landslides also contribute to floods. In 1971-2009, 362 flood events were recorded in the state. Though the flood frequency was high at certain periods, the overall trend shows an increase in flood events in the state. The spatial distribution of floods in the state is shown in Figure 3 (left). 

Figure 2 Flood frequency and trend in Himachal Pradesh from 1971 to 2009

 

Figure 3 Spatial distribution of floods (left) and landslides (right) in Himachal Pradesh (Source: Simrit Kahlon, 2014)

 

The state also has an established history of landslides. Landslide activities in the past were majorly associated with earthquakes and extreme rainfall events. As per the Government of India (2003), nearly 97.42% of the state’s geographical area is prone to landslide hazards. Historic landslide locations and frequency are shown spatially in Figure 3 (right). The decadal frequency of landslides in all the districts has risen since the 1980s, refer to Figure 4. In the 1990s, 219 events were recorded in the state, at an annual average of about 22 events. In comparison, 474 events were recorded in the 2000s, at a yearly average of about 47 events per year. Table 1 shows a clear increase in the decadal distribution of floods and landslides in the state from the 1980s till the 2000s.

Figure 4 Landslide frequency in Himachal Pradesh from 1971 to 2009 (Source: Simrit Kahlon, 2014)

 

DecadeTotal LandslidesDecadal AverageTotal floodsDecadal Average
1980-1989626.2343.4
1990-199921921.915215.2
2000-200947447.411311.3

Table 1 Decadal distribution of landslides and floods (Source: Simrit Kahlon, 2014 & Chandel et al., 2014)

State Calamity in 2023

Himachal Pradesh and other neighbouring states experienced torrential rains and landslides during the 2023 monsoon season. Himachal Pradesh was worst hit and bore the brunt of the rain. As per the weather department, Himachal has received 249.6 mm of average rainfall between July 1 and July 11 compared to the normal of 76.6 mm, an excess of 226 per cent and the highest for a 12-day period since 2005. In particular, the Kinnaur district received 500 per cent excess rains, followed by Solan, Sirmaur, Shimla, Bilaspur and Kullu districts with 426, 367, 360, 325, and 283 per cent excess rainfall. On August 18, the Himachal state government declared the rains a ‘state calamity’ and the whole state a ‘natural calamity affected area’. According to the government data, 72 flash floods were recorded in the state from the onset of monsoon on June 24 until September 4, 50% of which occurred from July 8-10 only (IMD, Shimla Centre). In comparison, only ten flash flood events were recorded in 2020, see Figure 5. Cloudbursts were reported in the Tunag, Pundoh and Seraj districts, and 131 landslide incidents were reported across the state. Unprecedented extreme rainfall and rainfall-related catastrophic events, cloud bursts, landslides and flash floods demolished buildings, damaged bridges and washed off several vehicles.

Figure 5 Frequency of flash floods from 2020 till 2023

DEVASTATION AND IMPACT

The 6th Assessment Report by the Intergovernmental Panel on Climate Change (IPCC) has clearly stated that the Indian Himalayan region (IHR) and Indian coastal region are at high risk from climate change. As many as 348 people have died, and 336 have been injured since June 24 due to monsoon-led natural calamities such as extreme rainfall, cloudbursts, landslides, and building collapses. The State Disaster Management Department said that nearly 2,230 houses were fully damaged, and 9,819 were partially damaged (retrieved from the Indian Express articles/reports on the events). The monsoon-led calamities have also disrupted roads, power lines, communication networks and railway lines. About 1,200 roads were blocked or inundated due to landslides and floods in the state.

We used the Sentinel-1 SAR data to map the flood extent of the affected area in Google Earth Engine. This was achieved by comparing the before-flood (June) satellite imagery with after-flood satellite imagery (July-Aug). Figure 6 shows that major flooding happened around the Beas River in the Kangra district and the Sutlej River in the Bilaspur district. An assessment at the district level shows that 368 km2, about 6.4% of the district area, got flooded in Kangra district (see Figure 7), and in the case of Bilaspur district, 69 km2, around 5.9% of the district area got flooded (see Figure 8). 

Figure 6 Flood area extent in Himachal Pradesh

Figure 7 Flood area extent in Kangra district
Figure 8 Flood area extent in Bilaspur district of Himachal Pradesh

We have also assessed the extent of damage to the vegetative cover in the state using the Normalized Difference Vegetation Index (NDVI) on Sentinel-2 multi-spectral imagery, see Figure 9. The land cover changes were assessed for five classes, of which three classes are Sparce Vegetation (Crops and grass), Moderate Vegetation (Agroforestry) and Dense Vegetation (Forests); see Table 2 for the changes in the area under each class.  The results show that approximately 3956 km2 of vegetative land, about 7.1% of the state, has been converted to wasteland or fallow land after the floods. In particular, there is a reduction of 5952 kmof forest land in the state. 

Figure 9 NDVI maps of Himachal Pradesh highlighting the extent of vegetation damage. Top left: Before flood, Top right: After flood, Below: Difference image highlighting the damage
ClassesDescriptionBefore floods (in km2)After floods (in km2)
Non-VegetationWater (deep & shallow); sand2613927625
Waste LandFallow/Wasteland650610462
Sparse VegetationCrop, grass32744373
Moderate VegetationAgroforestry71566569
Dense VegetationForest12518

6566

Table 2 Land cover classification of Himachal Pradesh Using Sentinel-2 and NDVI. Note: Total area of Himachal Pradesh is 55673 km2

A similar analysis is conducted for the most affected districts in the state. In the Kangra district of Himachal Pradesh, about 1238 km2 of land under crops & agroforestry was affected by the floods, which is about 21.5% of the district and 46% of the crops & agroforestry cover, refer to Table 3 and Figure 10.  In Solan district of Himachal Pradesh, about 172 km2 of land under crops & agroforestry was affected by the floods, which is about 9% of the district and 35% of crops & agroforestry cover, refer to Table 4.  In Shimla district of Himachal Pradesh, approximately 1301 km2 of forest land was affected by the floods, which is about 25.35% of the district and 81.5% of the total forest cover, refer to Table 5.  In the Mandi district of Himachal Pradesh, approximately 1278 km2 of forest land was affected by the floods, which is about 32.3% of the district and 72% of the total forest cover, refer toTable 6. The results show that the floods impacted vast areas under crops, agroforestry and forests. 

Figure 10 NDVI maps of Kangra district of Himachal Pradesh highlighting the extent of vegetation damage. Top left: Before flood, Top right: After flood, Below: Difference image highlighting the damage
ClassesDescriptionBefore floods (in km2)After floods (in km2)
Non-VegetationWater (deep & shallow); sand13281820
Waste LandFallow/Wasteland510825
Sparse VegetationCrop, grass1467500
Moderate VegetationAgroforestry1223952
Dense VegetationForest21771608

Table 3 Land cover classification of the Kangra district in Himachal Pradesh Using Sentinel-2 and NDVI. Note: Total area of Kangra district is 5739 km2

ClassesDescriptionBefore floods (in km2)After floods (in km2)
Non-VegetationWater (deep & shallow); sand182596
Waste LandFallow/Wasteland300491
Sparse VegetationCrop, grass221202
Moderate VegetationAgroforestry466313
Dense VegetationForest787354

Table 4 Land cover classification of Solan district in Himachal Pradesh Using Sentinel-2 and NDVI. Note: Total area of Solan district is 1936 km2

ClassesDescriptionBefore floods (in km2)After floods (in km2)
Non-VegetationWater (deep & shallow); sand15502410
Waste LandFallow/Wasteland9141429
Sparse VegetationCrop, grass348465
Moderate VegetationAgroforestry724532
Dense VegetationForest1595294

Table 5 Land cover classification of Shimla district in Himachal Pradesh Using Sentinel-2 and NDVI. Note: Total area of Shimla district is 5131 km2

ClassesDescriptionBefore floods (in km2)After floods (in km2)
Non-VegetationWater (deep & shallow); sand5081720
Waste LandFallow/Wasteland445760
Sparse VegetationCrop, grass297381
Moderate VegetationAgroforestry918584
Dense VegetationForest1780502

Table 6 Land cover classification of Mandi district in Himachal Pradesh Using Sentinel-2 and NDVI. . Note: Total area of Mandi district is 3950 km2

Is climate change alone to be blamed?

Climate change must have increased the intensity and frequency of extreme weather events, but is climate change alone to blame for all the devastation in Himachal Pradesh? The high impact of the rains was observed in the areas with high infrastructure development, deforestation for infrastructure and hill cutting for road widening. Mega hydropower projects and several dams were constructed in the fragile and eco-sensitive zones of the state. As per the 2022 landslide risk assessment report by the Himachal government, 77 blocks having 18,577 villages are landslide-prone. As per the experts, the reason for that is deforestation and the replacement of old stone and clay houses with concrete ones. An investigation by India Today revealed that many buildings that collapsed or were damaged in the floods were constructed on river banks or active floodplains by encroaching. The revenue records have also not defined the river boundaries, which gave rise to illegal constructions, threatening ecosystems and human life. Thefloods have also brought attention to the illicit mining and construction activities on the river banks. Tourism rush, rapid urbanization and unplanned infrastructure development are the major causes of massive devastation in the state.

Mansi Asher, who has published several papers on the changing climatology of Himachal Pradesh, said, “There is enough data from the department of science and technology of Himachal government to suggest that frequency of cloudbursts have increased, and so have landslides. The maximum impact was seen near the infrastructure sites which disturb the hills.”

Are we prepared?

The Himalayan region is a dynamic landscape and is at a high risk from climate change. The people living in these areas are prone to high seismic activities, cloudbursts, floods, extreme rainfall events, and forest fires. Clearly, massive efforts are required to protect the people and infrastructure in the Himalayan region from climate change disasters. The monsoon floods in Himachal have caused massive devastation, and the state is in need of an effective multi-hazard preparedness and disaster mitigation programme. 

Need for climate vulnerability assessments at village level

An effective disaster mitigation programme will have several components. Some of the major components include hazard mapping, hazard impact assessments, vulnerability assessments, risk assessments, and deriving mitigation strategies based on cost-benefit analyses. Vulnerability assessments are an inevitable prerequisite for disaster risk reduction and climate change mitigation measures. Climate change vulnerability assessments at the community level or village level will reinforce the disaster preparedness of the state. Village-level vulnerability and risk assessments will assist policymakers and decision-makers in effectively increasing the adaptive capacity and preparedness towards extreme weather events. It also helps in prioritizing the villages for resource allocation. It also helps in community-based disaster management, i.e., encouraging communities at risk to get engaged in all phases of disaster management. 

Sustainable land-use planning

Another component that needs attention is land-use planning. Sustainable land-use planning, which encourages people living in the most vulnerable areas to move, is essential. Sustainable Land Use Planning for urban climate resilience includes:

  • limiting development in hazard-prone areas
  • ensuring that the built environment can withstand a range of natural disasters
  • helping to preserve natural ecosystems
  • protecting communities against hazards
  • promoting nature-based measures for adaptation
  • educating stakeholders and decision makers about risks and opportunities and fostering dialogue about adaptation

In Himachal, several houses were illegally constructed in the flood plains and river banks. They are at high risk from future climate hazards. The government needs to bring strict land-use planning that encompasses the disaster and climate risks.

We also need to update our risk assessment methodologies and develop disaster mitigation strategies using the geographic information system (GIS) and remote sensing technologies. Web-GIS-based decision support systems are extremely helpful for governments, research organizations, companies, communities, and NGOs to transfer knowledge and expertise, and share the available data.

References:

https://www.researchgate.net/publication/298274899_Landslides_in_Himalayan_Mountains_A_Study_of_Himachal_Pradesh_India

https://www.researchgate.net/publication/303436834_Flood_Disaster_in_Mountain_Environment_A_Study_of_Himachal_Pradesh_India

https://indianexpress.com/article/cities/chandigarh/dead-missing-heavy-rainfall-batters-himachal-pradesh-mandi-district-8905546/

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