CLOUDBURST

Kumar Prafull 06AR1003Ranjitha Shivaram 06AR1004

Index

Defining characteristicsCausePast occurencesVulnerable areasDamage and effectsPredictionPreventionDisaster management

Defining characteristicsLarge quantity, small area, short duration

extreme form of rainfall, sudden aggressive rainstorm / thunderstorm.localized weather phenomena limited to a small geographical area, usually not exceeding 20–30 sq. km.lightning and thunder, sometimes mixed with hail.short period of time (normally lasts no longer than a few minutes).rainfall rate equal to or greater than 100 mm (4.94 inches) per hour.occur most often in desert and mountainous regions, and in interior regions of continental landmasses.capable of creating disasters- flash floods, landslides.

Cause

Cu mulus

•Sun heats earth’s surface.

•Adjacent air gets heated, rises.

•Gets cooled at height due to adiabatic expansion , condenses to form a cumulus cloud.

•Topographical conditions like steep hills favour the formation of these clouds.

Mature

•Cumulus cloud grows, drops become heavy.

•Rain starts when the rising air can no longer hold it up.

•Langmuir precipitation process in which large droplets grow rapidly by coagulating with smaller droplets which fall down slowly.

•Hail can occur if the cooling is sudden and intense.

• New cool air enters the cloud and descends, creating a downdraft.

•This cloud has become a cumulonimbus cloud because it has an updraft, a downdraft, and rain.

Dissipation

•Downdrafts in the cloud begins to dominate over the updraft.

•Warm moist air can no longer rise, cloud droplets can no longer form.

•The storm dies out with light rain as the cloud disappears from bottom to top.

Process

Process

Cumulus stage

Mature anvil-shaped cumulonimbus cloud

Cloudburst

Past occurences – IndiaPlace Date Injury

Himachal Pradesh August 31, 1960 103 deaths

Badrinath to Haridwar Uttarakhand

July, 1970 An entire village was swept away.

Shimla district, Himachal Pradesh

August 15, 1997 115 people were killed

Mumbai and other regions of western India

26 July, 2005 950 mm (37 in) in 8-10 hours,complete paralysis of India's financial centre.

Leh August 6, 2010 179 persons dead and over 400 injured

Almora in Uttrakhand September 15, 2010

Drowned two villages, one of them being Balta

India – vulnerable areas• Cloudbursts in India occur when monsoon clouds associated with low-pressure

area travel northward from the Bay of Bengal across the Ganges plains onto the Himalayas and ‘burst’ in heavy downpours(75–100mm per hour).

• The states of Himachal Pradesh and Uttaranchal are the most affected due to the steep topography.

Damages: Primary and secondary effects

CloudburstFlash floods

Landslide

Loss of lifeLoss of propertySiltation and sedimentationHabitat destruction

Nature of damagesCloudburst:• The extent of damage depends heavily on the terrain that is

receiving the downpour.• Severe localized flooding and waterlogging, isolation of low-

lying areas• Disruptions in communication• Localized power outages• Transportation severely affected

Nature of damagesCloudburst:• High speed-winds can damage or lift off the roofs of buildings.• Destabilization of soil, erosion and landslides• alternating wind pressures can lead to deformation of the vertical structure

Nature of damagesResultant flash floods:• direct damage during a flood from inundation, high velocity flow, waves, erosion,

sedimentation and/or flood-borne debris• degradation of building materials, either during the flood or sometime after the

flood• contamination of the building due to flood-borne substances or mold.• Service damaged: septic tanks, cesspools, pits, and leaching systems.

Pre-disaster preparedness: Prediction

• No satisfactory technique due to small scale. • A very fine net work of radars can detect, prohibitively expensive.

– Requires high-resolution numerical models and mesoscale observations, high-performance computers and Doppler weather radar.

– Both thunderstorms and cloudbursts had similar radar signatures making it difficult to identify the cloudburst.

• Only the areas likely to receive heavy rainfall can be identified on a short range scale.

• Much of the damage can be avoided by way of identifying the areas and the meteorological situations that favour the occurrence of cloud bursts.

• and requires

Pre-disaster preparedness: Planning strategies

• Location: avoid areas of accelerated winds.– Relocation of existing structures to less-prone areas– Appropriate location of new structures

Zoning– Availability of high ground within a community complex– Placement of important functions on higher ground or upper floors– Important services: communication, electricity, clean water supply protected as far as

possible from disruption

Pre-disaster preparedness: Planning strategies

Hazard resistant design & Retrofitting– Anchoring the roof – wind resistance– Avoid roof materials that are light and susceptible to wind damage – metal sheets, light

trusses.– Building openings should be protected with shutters or temporary covers of adequate

design.– Critical facilities should build storm shutters into the design of the building.– Limited use of large glass facades especially in the dominant wind directions.– Strengthen the building envelope – bracing to prevent deformation– Higher strength utility poles and additional guy wires installed.– Boat shelters be developed to protect boat stock.

FLASH FLOODS• Watercourses passing through settlements areas should be properly configured and lined

with concrete.• Existing bridges should be inspected to determine which ones are too low or which have

support pillars within the watercourse channel. Where possible these should be replaced as these features restrict water flow and cause the channels to be easily blocked with debris.

• Future bridges should not be built with these undesirable features.• Buildings constructed adjacent to watercourses should be elevated to prevent potential

flood inundation.• Critical facilities should not be located adjacent to watercourses.

Pre-disaster preparedness: Planning strategies

LANDSLIDES • Detailed slope analysis should be carried. • Appropriate cut slope design for houses on hill.• Locations prone to recurrent slope failures shouldbe examined with the view to stabilizing the slopewith structural support.

Recognize the areas prone to landslide

Pre-disaster preparedness: Planning strategies

Detailed slope analysis

Thank you.