On September 21, 2018, Cyclone Daye struck the Andhra–Orissa coast; with heavy rain and winds that touched 150 km/h, a 0.5 m storm surge flooded coastal areas. Last fortnight, Super Typhoon Mangkhut hit the Philipines and caused widespread damage. On September 15, 2018, the raging Hurricane Florence landed on the east coast of USA; thousands of inhabitants had to be evacuated. In 2005, Hurricane Katrina had played havoc in USA by overtopping embankments. Time and again, persistent natural extreme physical events around the world seem to catch the authorities off guard.
Natural hazards can be classified into broad categories: Geological hazards are driven by geological/earth processes and includes earthquakes and volcanic eruptions. Meteorological hazards are driven by meteorological / weather processes, in particular those related to temperature and wind as heat waves, cold waves, cyclones, hurricanes, and freezing rain. Hydrological hazards are driven by hydrological (water/ocean) processes causing floods, droughts, mudslides, and tsunamis.
The Disaster Management Act (Ministry of Law and Justice, 2005) defines disaster as a catastrophe, mishap, calamity or grave occurrence in any area, arising from natural or manmade causes resulting in substantial loss of life, destruction of property, or degradation of environment. However, a fundamental concept needs a review. Every time a natural phenomenon creates havoc, it is labeled as “natural disaster”. A common fallacy is that floods, cyclones and earthquakes are disasters. These are hazards, derived from natural events which are potentially destructive, and end as tragedies if and when a community is afflicted. Therefore, whenever humans come in the way of powerful natural forces, a major catastrophe is certain.
According to the urban development authorities, there has been an increasing trend of urban flood disasters in the country. A grim situation was noted in Kerala in 2018 and despite multiple creeks and backwaters that symbolizes Kerala, excess rain water could not find its way out into the sea. Urban flooding appears the major natural hazard that has affected the Indian populace during the last few decades. As such, it is a matter of shame that cities located along the sea front could not get rid of excess water that poured upon them.
What type of natural hazards can impact Goa? The vulnerability map of the Geological Survey of India (1935) places the west coast of India in the least active to moderate seismic zone. Subsequent updated maps by the National Centre for Seismology have classified the west coast of India as a Moderate Damage Risk Zone. Although the Uttarkashi and Latur earthquakes of the 1990’s are remembered by all, the most recent devastating tremors affected Kashmir in 2005 where 130.000 people perished. Goa was jolted by the Koyna earthquake in December 1967; except for cracks in some houses the damage was negligible. Since then, the geological crust of Goa has remained relatively peaceful in terms of seismicity.
During the first week of July 2018, within a span of 24 hours, the state witnessed three landslides at Khandepar, Ponda and Borim. Also, the road works at Cortalim led to the collapse of an irrationally created vertical hill cut. The Bogda area near Vasco is prone to landslides and every year the municipal authorities served notices to vacate houses in that locality. Around Panjim, the slopes of Altinho hillock have become a perennial hazard zone as land slips recur almost every year. The Konkan Railway line has witnessed annual mud flows along the hilly sections, even 30 years after the line was commissioned. Landslides have been an annual feature during monsoons. Such incidents prove that rampant hill cutting without following proper scientific methods invariably culminates in disasters with monetary losses.
In comparison, flooding and inundations caused due to excessive rain constitutes the foremost natural hazard in Goa. Cyclones are unlikely along the Goa coast, although Phyan (2010) and Ockhi (2017) did trigger abnormal sea levels. Also, marine incursions due to high spring tides have invaded the beach in recent times. Flooding around Panjim city in 2005 and 2010, and the Canacona flooding episode is long forgotten. On July 12, 2018, Miramar residential areas were under 50 cm of water; excess water could not empty itself. Similarly, inundations of lowlands in Salcette and overtopping of river banks at Paroda and Bicholim is an annual affair.
Can urban flooding be avoided? The characteristics of landforms govern the impacts of flooding on people. The major factors that control the damage potential of storm waters are topography, elevation, antecedent drainage, and the role of natural systems, the wetlands in particular. However, frenzied development has drastically changed the landscape of Panjim, for example. The St Inez creek is choked beyond redemption; the Mala lake resembles a bombed site; settlements are encouraged in dangerously low-lying areas. The natural drainage systems which were in place for centuries in the khazans of Salcette have been altered. Since outlets are blocked, rain water accumulates, levels rise and ultimately invades people’s homes. As such, occupying wetlands obviously puts humans in harm’s way.
Wetlands, swamps and natural depressions are nature’s flood reservoirs as channels, lakes and ponds can contain and distribute flood waters. Such interlinked drainage systems are bound to alleviate the impacts of heavy rainfall by receiving, accommodating and leading excess waters back into the sea. For this reason, wetlands have to be designated as critical areas to be preserved.
(Dr Antonio Mascarenhas is a former Scientist, NIO, Goa)