Natural Hazards of Assam

by

                              

Assam and Entire North Eastern India has a unique and unstable geological Conditions which makes it prone to various natural disasters and also Assam has witnessed some of the hazards or disasters which are due to anthropogenic reasons. Disasters causes disruption to life and property and creates a havoc among the people. Disasters wash away the gains of development and not only Human beings are affected but also entire Biodiversity is affected. For Ex- recent floods in Assam cause a lot of damage to the population of Rhinos in Kajiranga National Park.

A review of the past disasters indicates that the state had to bear the devastations of two natural disaster floods and earthquake.

Natural Disasters

  • Earthquakes
  • Floods
  • Landslides
  • Erosion
  • Wind and Cyclone
  • Fire

Earthquakes

As per the Tectonic Theory of Plates, Assam lies in the eastern part of the Indian Plate. This is the point where the Indian plate is thrusting underneath the Eurasian Plate creating a subduction zone. This makes the state of Assam fall under the seismic zone V which makes the entire State prone to earthquake of moderate to very high intensity. Among the large earthquakes in this region were the events in 1869 and 1897. The 1897 earthquake is well known for the dramatic accounts of violent up throw during the shock.

Combined with this hazard, the haphazard and uncontrolled growth of cities has made things worse. There is a famous Japanese proverb that Earthquakes do not kill people buildings do. Rising Urban population combined with poor quality and ill-maintained infrastructure without following Zonal and Building regulations increases the risks to earthquakes in the urban centres. Moreover, urban infrastructure is often designed and constructed without satisfying minimum safety standards.

Flood

Assam lies in the middle of the Brahmaputra and Barak basins. The Brahmaputra basin is one of the largest river basins in the northeast region of India. The Brahmaputra Valley in Assam is one of the most hazard-prone regions of the country, with more than 40% of its land (3.2 million hectares) susceptible to flood damage. This is 9.4% of the country’s total flood-prone area. About 7% of land in the state’s 17 riverine districts has been lost because of river erosion over the past 50 years.

Flood hazard risk in the state is due to a blend of numerous natural and anthropogenic factors. The important cause for frequent occurrence of flood in this region is the extremely dynamic monsoon rainfall regime and the unique physiographic setting.

The water yield of the Brahmaputra basin is among the highest in the world. This, together with the limited width of the valley and the abruptly flattened gradient, leads to tremendous drainage congestion and resultant flooding. The Brahmaputra valley had experienced major floods in 1954, 1962, 1966, 1972, 1974, 1978, 1983, 1986, 1988, 1996, 1998, 2000 and 2004.

The floods are caused by the runoff of extremely heavy rainfall during the monsoon and high sediment loads from upper watersheds that are geologically unstable and degraded because of deforestation and changing land use. The flood combined with river erosion has significant impacts each year.

Landslide

Landslides are sudden, short-lived geomorphic event that involves a rapid-to-slow descent of soil or rock in sloping terrains. It can also be caused by excessive precipitation or human activities, such as deforestation or development that disturb natural slope stability. Landslides are caused when the stability of a slope changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone.

Assam is located on the Himalayas, which are the recent foundation of mountain history and are geologically unstable; they are seismically very active therefore are still in the upheaval stage . As mentioned the state has a history of earthquakes. These earthquakes are usually accompanied by damaging landslides in the region .

 

Erosion

The Brahmaputra basin is an example of an extremely heterogeneous watershed with complex topography, high spatial variability in land cover.  Additionally, the climate is complex within the catchment because of the altitudinal range, the geographical location and the influence of the South Asian monsoon systems. Further, the tectono-sedimentary province along the Brahmaputra river valley in the state of Assam is near about 720 km long and 90 km wide with high variation in elevation which is home for nearly 26 million people.

 

The above factors give rise to riverbank erosion which has been a regular phenomenon in Assam. Erosion history of Assam indicates that between 1912 and 1996 around 868 sq.km. of land was lost to bank erosion; averaging to about 10.3 sq. km. of area lost per year.

Further, significant erosion occurred in Assam due to Brahmaputra river between 1914 to 1975. The bank line of the Brahmaputra is extremely unstable consisting mostly of fine sands and silts. Large scale slumping of river banks does take place when the level falls after a flood. Further, the braided nature of the Brahmaputra adds unpredictability to erosion problem making it more serious.

 

The extent of loss to the bank erosion varies from year to year depending on the severity of floods in the state. Majuli, the largest river island in the world is now seriously affected by the erosion and is facing the threat to existence.

 

Wind and Cyclone

Assam is situated in the north eastern direction of Bangladesh which is highly prone to cyclone/winds. Every year about 60% of the area affect by cyclone in Bangladesh.

Due to the location aspect, districts like Dhubri, Gaolpara, Hailakandi, Chachar and Karbi Anglong are more prone to cyclone/winds. Districts namely Kokrajhar, Bongaigaon, Kamrup, Barpeta, Nalbari, Darrang, Sonitpur, Nagaon, Marigaon, Lakhimpur, Dhemaji, Sibsagar, Jorhat, Golaghat, Dibrugarh, Tinsukia and Karbi Anglong are likely to experience wind speed of 50 m/s whereas districts like Hailakandi, Karimganj and Cachar has wind speed of more than 55m/s and are more vulnerable to cyclonic storms.

Occasional cyclones do occur in western Assam their severity is more during monsoon. According to BMTPC cyclone zonation, north-west districts of Assam lying in zone of high damage where wind speed can reach up-to 47

 

 

m/s. District very close to Bangladesh are in very high damage zone due to close proximity of Bay of Bengal (which is a cyclone basin). In this zone wind speed can reach up-to 55 m/s, can resultant into large scale damage.

 

Impact of Climate Change on Assam

The north-eastern region of India is expected to be highly prone to the consequences to climate change. The annual mean maximum temperatures in the region are rising at the rate of +0.11°C per decade. The annual mean temperatures are also increasing at a rate of 0.04°C per decade in the region.

 

The State of Assam is very much a part of the regional warming trend. However, there is no significant trend in rainfall for the region as a whole i.e. rainfall is neither increasing nor decreasing appreciably for the region as a whole. The summer monsoon rainfall is found to be decreasing over this region significantly during the last century at an approximate rate of 11mm per decade.

 

Extreme precipitation events (heavy rain storm, cloud burst) may have their own impacts on the fragile geomorphology of the Himalayan part of the Brahmaputra basin causing more widespread landslides and soil erosion. The response of hydrologic systems, erosion processes, and sedimentation in the Himalayan river basins could alter significantly due to climate change. Glacial recession is also linked to increased sediment load in rivers.

 

A number of major flash floods have occurred in this decade due to heavy rainstorms or cloud bursts in the state or in the upper catchments of the rivers in the neighboring states (Meghalaya, Arunachal Pradesh) and highlands in other countries (Bhutan, China).

 

The southern part of Nagaon district in central Assam valley and adjoining parts of Karbi Anglong form a rain-shadow zone where annual rainfall is as low as 800-1200 mm. Water scarcity is a potential constraint for the people living in these areas. Absence of effective irrigation systems or water harvesting practices adds to the vulnerability of the people. Lumding, located centrally in this zone shows a decline in rainfall at a rate of 2.15 mm per year. As a result water crisis might aggravate in this region in the coming years.

 

Institutional Framework and their roles and responsibilities

Roles and Responsibilities of State level arrangements

Assam State Disaster Management Authority

The Assam State Disaster Management Authority is constituted under the

chairmanship of the Chief Minister and other members will ensure interdepartmental coordination covering all aspects of DM. The State Authority has the responsibility of laying down policies and plans for DM in the State, recommend the provision of funds for mitigation and preparedness measures, review the development plans of different departments of the State and ensure that prevention and mitigation measures are integrated therein and issue necessary guidelines or directions as may be necessary.

State Executive Committee

The State Executive Committee (SEC) is constituted under the chairmanship of the Chief Secretary to the Government of Assam will assist the State Authority in the performance of its function and coordinate action in accordance with the state guidelines laid down by the State Authority and ensure the compliance of directions issued by the State Government under the Act.

 

Roles and Responsibilities of District level arrangements

District Disaster Management Authority

The District Disaster Management Authority constituted for every district in the

State is under the chairmanship of the Deputy Commissioner. The District

Authority shall act as the district planning, coordinating and implementing body for DM and take all measures for the purposes of DM in the district as per the guidelines laid down by the National and State Authority.

The District Authority will prepare the District Disaster Management Plans, review capabilities and preparedness measures, give directions to the concerned departments at the district level, organize and coordinate specialized training programmes for different level of officers, employees, voluntary rescue workers and take all such measures as may be appropriate for a holistic and pro-active approach to DM.

 

Roles and Responsibilities of Local level arrangements

Local Authorities

The local authorities include the PRIs, Municipalities, Urban Local bodies,

Cantonment boards etc. the local authority will ensure that its officers and employees are trained for disaster management, resources relating to DM are so maintained as to be readily available for use in the event of any disaster situation; construction practices under it or within its jurisdiction confirm to the standards and specifications laid down for prevention of disaster and mitigation; and carrying out relief, rehabilitation and reconstruction activities in the affected areas in accordance with the State Plan and the District Plan.

 

Disaster Management Plan

As per the DM Act 2005, Disaster Management means a continuous and integrated process of planning, organizing, coordinating and implementing measures which are necessary or expedient for-

  • Prevention of danger or threat of any disaster
  • Mitigation or reduction of risk of any disaster or its severity or consequences;
  • Capacity-building;
  • Preparedness to deal with any disaster;
  • Prompt response to any threatening disaster situation or disaster;
  • Assessing the severity or magnitude of effects of any disaster;
  • Evacuation, rescue and relief;
  • Rehabilitation and reconstruction;

Disaster Management plan at all levels will be drawn upon at the Local, District and State levels as well as by relevant departments with a mandate for DM functions to ensure coordination and holistic response to disaster. The plans will incorporate the inputs of all stakeholders for integration into the planning process.

 

List of ongoing initiatives

ASDMA has undertaken various activities to build a disaster resilient state. The list highlights select activities and is not exhaustive.

  • Flood early warning system (FLEWS)
  • Hazard Risk and Vulnerability Assessment
  • Revision of Assam Relief Manual (1976), renamed as Disaster Management Manual
  • Setting up of Disaster Information and Response Centre at Revenue Circle Level
  • Involvement of NGO’s and Ex-Service men in DM
  • Integration of Emergency Helpline Numbers
  • Revisiting the danger levels of major rivers of Assam
  • Equipping the Districts for better response during floods
  • Capacity building and awareness generation
  • Trainings and workshops for stakeholders (engineers, architects, doctors, PRIs, NGOs, volunteers in first aid & search and rescue)
  • State wide school safety programme
  • Technical projects undertaken by knowledge institutions in the State
  • Establishment of Assam Institute of Disaster Management (AIDM)\

 

 

APSC Notes brings Prelims and Mains programs for APSC Prelims and APSC Mains Exam preparation. Various Programs initiated by APSC Notes are as follows:- For any doubt, Just leave us a Chat or Fill us a querry