Friday, May 29, 2015

Midterm 2

Afghanistan is considered as a country prone to a number of natural disasters: earthquakes, flooding, drought, landslides, and avalanches.  Earthquakes are relatively frequent, being more frequent in the north and northeast, and often trigger landslides. Afghanistan is geologically located in the active part of the world where two tectonic plates, the Iranian Plate and the Eurasian Plate, meet. The Indian plate (northward-moving) is colliding with the southern part of the Eurasian plate at a rate of about 1.7 inches per year. Both the Iranian Plate and the Eurasian Plate consists of continental crust, which can neither sink nor be destroyed. Since Afghanistan is sitting on a collision plate boundary, it has created some of the world's highest mountains and causes slips on major faults that generate large and often devastating earthquakes. Every few years, a powerful earthquake takes place in Afghanistan and causes significant damage and fatalities in the war torn country where there is poor transport and communications. Modern seismograph networks show that earthquake activity is widespread throughout much of the eastern part of the country. In addition to the damage caused by strong shaking, earthquakes can trigger destructive landslides, especially in mountainous terrain, which is very common in much of northeastern Afghanistan. Earthquakes also cause damage from liquefaction, where water-saturated soil becomes unstable and liquefies, and from ground subsidence, where shaking causes shifting and settlement of the ground surface. 


As Afghanistan’s infrastructure is rebuilt and modernized and its natural resources developed, critical facilities and major construction projects need to be located and designed to take into account the potential adverse effects of natural hazards such as earthquakes. A lot of the earthquakes that take place in Afghanistan may not be massive but the lack of warning system, building codes, and preventive measures increase the number of casualties. Buildings/houses are built without any codes and a lot of times, in the rural regions, a lot of the locals build their own houses using mostly mud. Earthquakes don’t necessarily kill a lot of people but the high death tolls usually come from unsuitable building constructions.  Proper design of such facilities and structures will help ensure that Afghanistan’s new and reconstructed infrastructure is durable enough to survive the impact of major earthquakes, which will inevitably occur.
Researchers with the USGS Earthquake Hazards Project compiled extensive data on the location, size, and frequency of past earthquakes in Afghanistan, and examined satellite and aerial imagery to identify the locations of potentially active faults. This information was then used to create preliminary earthquake hazard maps that show the strength of probable ground motion caused by earthquakes at specific localities and nationwide. The level of ground motion is expressed as a percent of the acceleration due to the force of gravity (% g), which is a parameter that engineers often use as a guide in designing structures such as hospitals, dams, pipelines, and power transmission lines.




Every year, thousands of people die in Afghanistan from various natural disasters, but earthquake results massive destruction of building and human losses in the Easter region of the country such as Takhar and Badakhshan. Also, houses are usually made of mud by locals, and therefore, even minor quake results vast fatalities and destruction. Also, houses are poorly built in the mountain skirts of Hindu Kush where any minor earthquake could cause a vast destruction and casualties. In order to prevent Eastern area from injuries, construction of homes should be strictly limited and people should be informed about the hazards of active faults since they are not aware of the danger. Moreover, building codes in this area should require structures that framed in wood, steel, or have appropriately reinforced concrete, but construction of masonry walls made of bricks, concrete blocks, stone, and mud should be prohibited. Load bearing masonry walls of any kind are likely to shake apart and collapse during an earthquake, dropping heavy roofs on people indoors. House can be built to withstand severe earthquakes well enough to minimize the risk to people inside. Even if a properly frames buildings is severely damaged, it’s unlikely to collapse. Reinforced concrete often breaks in large earthquakes, leaving the formerly enclosed reinforcing steel free to buckle and fail.

Earthquakes are more frequent in the north and northeast and, therefore, the safest place where I would live would be in the southwest region of the country such as Kandahar, Helmand and Nimruz. 


Friday, May 1, 2015

Coastal Erosion in CA

 Societies worldwide are faced with new challenges in mitigating and adapting to the effects of climate change. One of the major environmental effects of global temperature increases will be a continued increase in the rate of sea level rise. Higher temperatures cause sea level rise through the melting of ice on land (eustatic increases) and through the thermal expansion of water (steric increases) (Cayan et al, 2008).
One of the direct physical outcomes of sea level rise is coastal inundation. While inundation will be more pronounced on low-lying, heavily urbanized coastlines, it will still affect the Monterey Bay area. In both Monterey and Santa Cruz Counties, urbanized areas directly adjacent to estuaries and the coast will be threatened by higher high tides. While the rise may not be a direct threat to infrastructure, businesses, or residences, it may overwhelm agricultural land, degrade wetland ecosystem services, and will raise the base level to allow for more devastating storm events. Wetlands that worked as flood barriers and groundwater filters will have less functional area. Natural wetland retreat due to the increase in base level will be halted by adjacent urbanization and hard barriers (Pethick, 2001). Saltwater intrusion can damage upstream ecosystems and water availability (EPA, 2008).


Some of the Monterey Bay’s major natural assets are its long sandy beaches, which act as natural buffers to coastal flooding and are important attractions for the dominant tourism industry. The littoral cells operating within the bay are highly active, but are not at equilibrium. The southern stretch of the beach, near Seaside, already has the highest average erosion rate in California (AMBAG, 2008). In addition, the dunes that work as a continued source of sediment and as a flood buffer during storm surge events have been eroding along the entire southern Monterey Bay coastline at up to six feet per year since 1970 (Hapke et al, 2006). Erosion rates are expected to increase due to rising mean sea level. Zhang et al (2004) found that the erosion rate on Atlantic Coast beaches is about two orders of magnitude greater than the rate of sea level rise.
Beach nourishment has been highlighted recently as a solution to coastal erosion; proponents of this alternative maintain that increasing beach width by physically adding sand to a beach buffers wave energy and slows retreat rates. Federal, state and local government agencies are pursuing this method as a way to protect property from erosion damage, but the costs are generally very high and the net, long-term benefits of beach nourishment will vary greatly depending on local conditions (Leonard et al. 1990). By far the most popular option to manage shoreline retreat in California has been the construction of coastal protection structures (also referred to as coastal armoring). Approximately 10% of California’s coastline is currently armored (Griggs in press-a). The complexity and significance of coastal armoring in California are evidenced by numerous scientific studies, involvement of non-profit organizations, such as the Sierra Club and the Surfrider Foundation, and media coverage of the issue, such as KQED’s Coastal Clash documentary (http://www.kqed.org/w/coastalclash/home.html). The costs of armoring can be significant; millions of federal, state and private dollars have been expended annually on shore 3 protection, which can cost anywhere from $1800 to $7600 per linear foot of coast (Griggs in press-a).