the goan I network
CANACONA
When the flash floods claimed 2 lives, thousands of livestock and caused extensive damage to property in Canacona taluka on October 2 ten years ago, authorities and people had been clueless on the causes for the unprecedented event in living memory.
The National Institute of Oceanography (NIO) later conducted extensive analysis and prepared not one but three reports highlighting the causes of the flash floods and recommending various measures to tackle such incidents in future.
The Canacona flash floods had claimed two lives in Poinguinim and over 2400 livestock, while 107 houses had collapsed, over 591 houses were damaged and over 1,000 houses were flooded. Over 4,000 farmers had also suffered losses to their crops and plantations. The estimated losses were placed at over Rs 100 crore.
The NIO had prepared three reports in 2011 after conducting field surveys and analysing data of the flash floods.
The Canacona Flash Floods Study Committee (CFFSC) had blamed the 271 mm of rainfall on October 2, 2009 as the prime reason for the flash floods.
Stating that though such events cannot be prevented, the experts suggested that the State should focus on awareness and preparedness to minimise the impact of similar intense-rainfall events.
RECOMMENDATIONS
The general recommendation was that well-known practices in forest management to prevent mudslides (afforestation of mountain slopes, etc) and in river management (de-silting of riverbeds) should receive emphasis and increased investment.
The NIO recommended that areas vulnerable to mudslides should be mapped and a site-specific disaster management plan to face them should be in place at each location with high vulnerability.
Besides, areas with high vulnerability to flooding due to an intense precipitation event should be identified and a disaster management plan should be evolved at locations that are particularly vulnerable.
The NIO also felt that a mechanism to keep a careful watch should be in place whenever a situation arises with high potential for an intense precipitation event in a vulnerable area.
The Meteorological Centre of the India Meteorological Department (IMD), Panaji should form the nerve centre of such a watch.
Experts had also recommended that the State of Goa should make IMD’s ‘Cyclone Warning Dissemination System’ operational in the State.
FIRST REPORT
The first report by Kessarkar, Srinivas, Suprit and Chaubey proposed a method to map landslides. It describes the geological reasons behind the landslides that occurred in Canacona taluka.
The CFFSC noted that these landslides occurred on steep slopes; the cascading water triggered the landslides.
The report listed factors identified as important for landslides in this area and prescribed a method to estimate a Landslide Potential Index and to prepare a landslide-susceptibility map.
SECOND REPORT
The second report by Suprit, Kalla, and Vijith, presented a methodology for assessing flood risk and issuing a warning during an intense-rainfall event.
The method analyses topography for river flow and for converting rainfall to river flow.
It uses an open-source Geographical Information System (GIS) called GRASS and a simple hydrological model called the rational method.
Based on this method and using rainfall data from online Automatic Weather Stations (AWSs), an algorithm is developed for a flood-watch.
The potential discharge computed from the data using the rational method is used to develop a simple, graphical method for issuing a warning.
THIRD REPORT
The third report by Sundar presented the outline of a watch-keeping mechanism with the Panaji observatory of the IMD as its nerve centre.
Sundar used elevation data from the Shuttle Radar Topography Mission (SRTM) and publicly available geographical information such as Google Earth and Google Maps to ascertain which regions of Goa are likely to be prone to floods.
The report stated that an evaluation of the existing network of AWSs and Automatic Rain Gauges (ARGs) would leads to identification of sites where AWSs need to be located in order to augment the existing network in the State.
