Risks of natural hazards and their consequence on environment.

Natural disasters are variations and extreme events which cause damage and destruction to human life safety, economic development, the living environment and resources. A natural hazard is a complex system with interactions between natural hazard-inducing factors (natural mutation factors) and the socio-economic system (the person property-environment-resource composite system) under certain conditions. Every ten years the death tolls reach 1 million and more millions of people are rendered homeless. Destruction to the global economy caused by natural disasters was to USD40 billion in the 1960s, USD70 billion in the 1970s and up to USD120 billion in the 1980s . Natural hazards regularly strike major cities in the world leading to numerous fatalities and billions of dollars of property and infrastructure damage each year. Recent examples include hurricane sandy which hit New York City and surrounding area in 2012, hurricane Harvey which caused severe flooding in Houston in 2017, each resulting in more than 100 deaths and Asian tsunami hit the coastal areas of the Indian Ocean bordering with Somalia. Climate scientists suggest that as global greenhouse gas emissions increase so too will the number and severity of natural disasters (IPCC 2012). Furthermore, as more economic activity clusters along ocean coasts, a greater share of population is now at risk of exposure to natural hazards (changnon et.al 2000:Rappaport & Sachs, 2013: pielke et al., 2008).