CHARACTERIZATION OF THE DAMAGES DUE TO CYCLONIC STORM EVENTS IN INDIAN COAST Ramakrishna Nallathiga Knowledge Manager Centre for Good Governance Hyderabad (INDIA) ASCE – EWRI Conference, Dec 18-20, 2006

Structure Introduction Motivation Methodology Results Comparison Formulation Establishment Results Comparison Caveats Implications

Introduction Monsoon is an important phenomena for India with reference to rainfall, which is important for agricultural production and natural resources It is the cyclonic storms that form in the seas along both the coasts which give rise to monsoon rainfall upon crossing of the coasts The crossing of cyclonic storms also causes severe rainfall in coastal zone, storm surges along coastline and very severe rainfall on mainland The crossing of cyclonic storms, therefore, leads to a variety of damages to: human population and settlements, agriculture and livestock, infrastructure and industries

Primary Impacts Secondary and Tertiary Impacts

Motivation The occurrence of cyclonic storms is not peculiar to Indian sub-continent, but common to several tropical countries, which are under the risk of storms and several other damages The damages on account of natural disasters, particularly cyclonic storms, has become an important area of concern to international agencies like the World Bank India has a good database of storm occurrences and crossings, but the information on the impacts i.e., damages, is still scattered, not complete and not well maintained. Event studies exist but few cross-sectional studies Given the rising importance of increasing damages associated with cyclonic storm events, this study made an attempt to characterize them in terms of storm characteristics.

Methodology Empirical study of the records of cyclonic storm events and damages/impacts Formulating relationships between storm characteristics and damage categories Correlation and Parametric regression analysis Statistical testing and Comparison with similar studies Implications (including limitations)

Formulation Damages due to the Cyclonic storms (D) are: (i) inversely related to Storm Pressure (P) (ii) directly related to Wind Speed (V) Or, simply expressed, Ds = f(Ps) and Ds = f(Vs) Upon examination of data, we modify it to Log (Ds) = f(Ps) and Log (Ds) = f(Vs) For testing, the mathematical forms are Log (Ds) = +(Ps)+  and Log (Ds) = +Vs +  With respect to s, we expect –ve sign associated with P and +ve sign associated with V

Establishment Examination of correlation among variables Simple bi-variate relationships through statistical regressions using data sets by estimating the coefficients (s) and their signs Examining the relationships in terms of statistical significance of parameter coefficients, goodness of fit of relation i.e., R square Comparing the explanability of the relationship with such experiments in the US

Results - Correlation Analysis Log (Deaths) Log (Crop area) Log (Losses) Log (Houses) Surface Pressure -0.57805 -0.02632 -0.4123 -0.66494 Wind Speed 0.576931 0.004396 0.234018 0.583475

Results - Regression Analysis Dependent Variables Log (Deaths) Log (Crop area) Log (Losses) Log (Houses) Independent Variables Constant 25.767 5.7878 27.652 33.138 Surface Pressure -0.0243*** -0.0008 -0.0246* -0.0292*** Goodness of Fit (R2) 0.3341 0.0007 0.17 0.4421 No. of observations (n) 38 13 19 21 1.0068 4.9693 2.5555 3.0888 Wind Speed 0.016*** 0.0001 0.0163 0.025*** 0.3328 2e-05 0.0548 0.3404 41 14 22 *** Statistically significant at more than 99% confidence level * Statistically significant at 90% confidence level

Comparison When compared to the similar functional relationships in the US e.g., Pethak and Atkinson (1987), it appears that the association between storm characteristics and two of the major impacts, mortality and damages (fixed property like houses), is more explainable in case of India but the strength of relationship is almost same. The association appears to be very poor in case of the US as evident from the explainability of the model fit (R2 values) shown in table 4, which are much lower than those corresponding in Indian context

Caveats The study concerned with direct impacts alone, but indirect impacts may also be significant and larger Other intervening variables (most local), such as land use, soil properties, type of crop and damage sustained, may determine the impact than storm characteristics alone The method is not useful for comparison across the time periods due to natural growth in many of the parameters like population, houses, livestock, agricultural crop area/production Normalisation of damages and such advanced methods may make the damages comparable but are plagued by data gaps of concerning variables The relationships also need to be extended to include other variables to make the models more robust and useful in the decision making with respect to management interventions/ strategies

Implications Nevertheless, the results point to the fact that most damage categories are related to the cyclonic storm characteristics This assumes importance as India has been experiencing some very severe storms, like some other parts of the world, albeit with lesser frequency Also, with rising intensity of storms, which is now attributable to global warming, the damages would also rise in future if warming lead to stronger storms The number of intense storms crossing the coasts has also been a worrying concern, but such effects appear to be variable with regions e.g., In India there was a decline in number in the last decade but they increase in the US Besides the risk arising from storm events, the vulnerability of human and natural systems, particularly on the coasts, might also rise, if current human population and human activities concentrate on coast and are exacerbated if there are severe local problems