General Hazards and Associated Risks in Kathmandu Valley

According to the Kathmandu Valley DRM Profile (EMI, 2005), the most frequent natural disasters in Nepal are flood, landslide, and fire causing loss of life and severe damage to property. The middle hills are mainly prone to landslides while the flat Tarai region is susceptible to flood and fire. While earthquakes are not frequent, historically, Nepal has experienced several destructive liearthquakes with more than 11,000 people killed in four major earthquakes just in the past century.

Eartuake 

Historically, Nepal has experienced several destructive earthquakes with more than 11,000 people killed in four major earthquakes just in the past century  A review of the seismicity and damages in Nepal reveal that damage intensities greater than or having same intensity (MMI) VI may recur every 21 years, damage intensities greater than or having intensities greater than (MMI) VIII may recur every 38 years, and the more extensive damage under (MMI) intensity IX may recur every 75 years.

Based on the earthquake catalog, Nepal faces one earthquake of Magnitude 7 or greater every 75 years, on average. Such magnitude earthquake could be extremely damaging to urban metropolises as demonstrated by the M7.0 January 2010 Haiti earthquake. Even more alarming is that since 1800 five (5) events of M>= 7 have affected Kathmandu. Recent damaging earthquakes in Nepal were recorded in 1980 and M8.3 in1934, with the first documented earthquake in 1255.

Flood, Landslide and Debris Flood

There are more than 6,000 rivers and streams in Nepal, most of which flow from north to south generally at high velocity due to steep river gradient. The majority of the larger rivers are snow fed from the Himalayas. Since the topography of the country is steep and rugged, with high-angle slopes and complex geology, large quantities of rainfall during the monsoon season lead to floods, landslides, and debris flows in a number of cities. Costly yet ineffective land conservation causes flooding and landslides. Unplanned settlements and structures built without consideration of natural hazards aggravate the situation. In addition, landslides caused by torrential rains add enormous volume to streams and rivers causing floods and debris flows downstream that kill numerous people and inflict immense harm to agricultural lands, crops, and properties. In July 1993, the Tarai region experienced a destructive flood which claimed the lives of 1,336 people and affected another 487,534. In 1998, floods and landslides struck various parts of the country, mainly the Tarai and middle Hill regions, killing 273, injuring 80, and impacting 33,549 families. The floods and landslides also ruined 45,000 hectares of crops. Similar flooding occurred in 1999 and continues to occur annually.

Fire

Fire occurs mainly between April and June during the dry season when it seldom rains and temperatures in the Tarai region reach higher than 35∞C. Fires are common to the rural Tarai and Hill regions where 90.8 percent of the total population lives in very poor housing conditions.

Houses in rural regions, especially Tarai, are composed of straw or timber and tend to be very close to each other, thereby increasing the risk of fire and fire spread. In 1999, a blaze killed

39 people, injured 10, and affected 1,065 families. The fire, with estimated total losses of NRs 45.23 million, destroyed 1,035 houses, 52 cattle sheds and 148 livestock.

Reference :

EMI (2010) Mainstreaming Disaster Risk Reduction in Mega Cities: A Pilot Application in Metro Manila and Kathmandu, Earthquake and Megacities Initiatives.