impact of geographical phenomena, Study Guides, Projects, Research of Geography

Download impact of geographical phenomena and more Study Guides, Projects, Research Geography in PDF only on Docsity! A Presentation By TYRESE BOBB & KIRAN RAMPERSAD Subject: Caribbean Studies Form: Upper Six The Impact of Geographical Phenomena Topic: Floods TYPES OF FLOODS  Riverine flooding. This usually occurs when a river overflows its banks. It is usually due to the volume of water within a body of water, such as a river or lake, exceeding its capacity and overflowing its banks. It can also occur when the velocity of the river is so high that it flows right out of the river channel, usually at bends.  Coastal flooding. The sea can overflow or overtop flood defenses such as sea walls, perhaps due to a heavy storm (storm surge), a high tide, a tsunami or a combination thereof. TYPES OF FLOODS/CON’TD  Flash flooding. This is a flood that rises and falls rapidly with little or no advance warning. Flash floods usually result from intense rainfall over a relatively small area.  Estuarine floods are induced either by a costal flood whereby flood water is driven into the estuary or the incident of coastal and slow rise flooding.  Urban flooding This occurs as a result of land development. Permeable soil layers are being replaced by impermeable paved surfaces, through which water cannot infiltrate. This leads to greater runoff being generated, which can make rivers out of roadways and ponds out of car parks. CAUSES OF FLOODS Types of Precipitation Events  Prolonged rainfall. When rain falls for a prolonged period of time, the soil can become saturated. When water is unable to infiltrate into the saturated soil, it is forced to flow over the soil, thus increasing surface runoff. Rivers that are unable to accommodate excess rain water overflow their banks onto neighbouring flood plains.  Intense/Heavy rainfall. When rain falls heavily; the rain drops hit the ground with a force. This can cause the rain drops to bounce off the soil instead of infiltrating into the soil. The water from the rain is then forced to flow over the surface instead, thus increasing the surface runoff. CAUSES OF FLOODS Influence of Human Activity  Deforestation. The lack of vegetation encourages water to flow over the surface rather than infiltrate into the soil thus increasing surface runoff.  Poor land use practices. Slash and burn agriculture, over-cultivation and over-grazing eventually cause the soil to become infertile and unable to sustain vegetative growth. Consequently, the lack of green cover encourages water to flow over the surface rather than infiltrate into the soil thus increasing surface runoff. CAUSES OF FLOODS Influence of Human Activity  Urbanization leads to the replacement of permeable soil with that of an impervious layer of pitch and concrete, through which water cannot infiltrate. This results in increased surface runoff which leads to flash flooding.  Improper waste disposal. Oftentimes, garbage that is not properly disposed enters into drainage systems and clogs drains. This obstructs the free flow of the water that enters into these drains causing water to back up during rainfall flooding the surrounding area. A build up of garbage can also obstruct the natural flow of water in rivers and streams. CAUSES OF FLOODS Influence of Human Activity/CONT’D  Quarrying is the clearing of land for the removal of aggregates (mainly sand and gravel) which is to be utilized in the construction industry. The action of quarrying leaves land bare and devoid of any trees and shrubs hence increasing surface runoff produced. CAUSES OF FLOODS Sea Level Changes  “Relative sea level change” refers to the height of the ocean relative to the land at a particular location. As relative sea level rises due to climate change one of the most noticeable consequences is an increase in coastal flooding. Flooding typically occurs during seasonal high tides and storms that push water toward the shore. In recent years, however, coastal cities are increasingly flooding on days with less extreme tides or little wind, even on sunny days. Floods are happening more often as rising sea level reduces the gap between average sea level and the height of the land.  This type of tidal flooding is expected to increase in depth, frequency, and extent in the United States during this century. CAUSES OF FLOODS Drainage Basin Characteristics • Drainage basin - the area of land drained by a river. • Catchment area - the area within the drainage basin. • Watershed - the edge of highland surrounding a drainage basin which marks the boundary between two drainage basins. • Source - the beginning or start of a river. • Confluence - the point at which two rivers or streams join. • Tributary - a stream or smaller river which joins a larger stream or river. • Mouth - the point where the river comes to the end, usually when entering a sea. CAUSES OF FLOODS A Diagram Showing the Drainage Basin Characteristics The Effects of Flood  L. Fontes de Meira and W. Phillips. “An economic analysis of flooding in the Caribbean: the case of Jamaica and Trinidad and Tobago” , Studies and Perspectives series-ECLAC subregional headquarters for the Caribbean, No. 78 (LC/TS.2019/55-LC/CAR/TS.2019/1), Santiago, Economic Commission for Latin American and the Caribbean (ECLAC), 2019; spoke of the potential effects in Trinidad and Tobago-Flooding in Tunapuna/Piarco and Chaguanas, a case study of St. Helena, Kelly Village and Charlieville. The Effects of Flood/Cont’d  Approximately 295,000 persons live in these two boroughs and are susceptible to primary or secondary impacts from yearly flooding events. In the Tunapuna /Piarco region, most of the popoulation was significantly affected by the 2018 flooding event. According to the Tunapuna/Piarco Regional Corporation (TPRC), the number of families displaced by the flood was around 2,600, not including those that did not report to the RC office.  Based on information collected from the Disaster Management Unit of the TPRC, events of this type are recurrent, as the area experiences on average 3 to 4 major flood events every rainy season. The recession of the floodwaters is typically slow in the lower areas and the problem can be aggravated by tidal factors with water being retained for up to 6 days. The borough of Chaguanas was relatively less impacted by the most recent flood event, but a similar pattern of flooding has been reported in the area. The Effects of Flood/Cont’d Effects of the Social Sectors  Families in the households affected by the 2018 October flooding received a “minor repairs and reconstruction grant” from the National Commission for Self Help. The assistance was provided in the form of a purchase order for up to a maximum amount of TTD 10,000.00 allowing people to buy building materials to replace damaged components of the house. Effects of the Social Sectors/Cont’d  As indicated in interviews with local schools and the Regional Corporations in both areas, the 2018 flooding event resulted in schools in the areas most affected being closed for an average of two days. Additionally, some schools were used as shelters for displaced families with larger closure periods10 . A visit to the St. Helena Hindu School affected by the 2018 floods, reported that the compound was under 3 feet of water for around 2 days, the most impacted the school has been in over 20 years.  School documentation, materials and furniture were severely damaged. The building structure was also affected causing minor damage to walls, doors and floors (figure 2). This particular school remained closed for one week and no extended teaching time was expected to recover the number of hour/classes lost. In an unofficial inquiry with school management, the damage resulting from the event was estimated at 15,000 TTD. Effects of the Social Sector/Cont’d  Based on this information, the potential hours of class lost by students over a one-year period were calculated considering the following assumptions:  (i) 3 major flood events occuring every rainy season;  (ii) school activities in the area are paralyzed for an average of 2 days for each event;  (iii) a school normal day has an average of 6 hours.  Based on the population residing in the area and the percentage of population attending an educational institution in the borough as per the 2011 census, the following losses were calculated: 36 hours of school per year for each student and an overall loss of 72,256.67 hours of class in Kelly Village/St Helena and 67,292 hours in Charlieville. On this basis, a total of nearly 140 thousand hours of school hours were lost yearly. Effects of the Infrastructure  Note that in this event there were no damage reported for infrastructure assets such as telecommunication, power, transportation, and water and sewerage. Losses were however identified in the power and water sector associated with damage in housing sector. With this percentage of affected housing, considering the average national electricity consumption (for 1-400kWh, 401-1000kWh, over 1000kWh) at current prices and assuming that the same percentage of houses are affected for a period of two weeks, the loss in terms of revenues forgone by electric power utilities during the period of disruption were observed for each area as: Kelly Village – TTD 54,199; St. Helena – TTD 66,630; Charlieville – TTD 90,306. Effects of the Economic Sectors/Cont’d  In the flooding event of 2018, two major business establishments in the area - the Kentucky Fried Chicken restaurant, and the American Stores – were closed for a period of two days. Moreover, both lanes of the Uriah Butler Highway, the main connection with larger urban centers in the country, became underwater with the traffic blocked for light vehicles, for a period of two days.  Considering the average income for small and medium sized businesses in the areas, as reported in the economic profile of the regional corporation, a decrease in business activities, even if for a short period, could have significant impacts on households. Moreover, given that a few settlements in Tunapuna/Piarco are dormitory communities, many of the residents engaged in employment outside of the area of residence were affected by road disruptions. The Effects of Flood Cont’d  H.Martin,M.Ellis and C.Delpesh. “Risk Perception in a Multi-Hazard Environment: A Case Study of Maraval, Trinidad, spoke of the worst disaster experienced by the community. 60.5% of the respondents had past experiences with a disaster, while 39.5% had no prior experience. Of those who experienced disasters,75.0% experienced flooding, 33.3% experienced landslides, 8.3% experienced storms and 22.2% experienced earthquakes.  When asked to identify the natural disaster posing the greatest threat, 30.3% indicated that floods posed the greatest threat, 28.6% indicated landslides, 9.2% indicated storms and 5% indicated earthquakes. This sense of dread is being associated with frequency and past experience as the area is known to be frequently affected by floods and landslides. Ways to Mitigate the Effects of Floods  C. Benjamin (2019), Institutional Capacity to Manage the Risk of Flood Disaster: A Case Study of the Tunapuna/Piarco Regional Corporation in Trinidad and Tobago, discussed the following ways to mitigate the effects of floods. They are as follows:  The disaster management coordinator should be responsible for coordinating early warning, shelter and evacuation.  The use of loud hailers or door-to-door visits to warn residents of an impending disaster event.  The disaster management coordinator is responsible for managing the corporation’s emergency operations centre during a disaster. Ways to Mitigate the Effects of Floods/Cont’d  L. Fontes de Meira and W. Phillips. “An economic analysis of flooding in the Caribbean: the case of Jamaica and Trinidad and Tobago” , Studies and Perspectives series-ECLAC subregional headquarters for the Caribbean, No. 78 (LC/TS.2019/55-LC/CAR/TS.2019/1), Santiago, Economic Commission for Latin American and the Caribbean (ECLAC), 2019, discussed flood mitigation measures in their case study in the following ways:  The plan to implement a TTD1 million flood hazard alarm system with water sensors in the most relevant streams in the area.  Maintenance and retention ponds Ways to Mitigate the Effects of Floods/Cont’d  The purchasing of two (2) mini excavators to clear water courses at an initial approximate cost of TTD 500.000.  A planned allocation of TTD 35 million for the implementation of projects under the National Programme for the upgrade of Drainage Channels.  An investment of TTD 9 million will also be made for the commencement of projects under the Major River Cleaning Programme (Ministry of Planning and Development, 2017). Conclusion  In this presentation we would have addressed the topic on floods, which is an impact of geographical phenomena on the environment and all things and humans that resides on it. In our presentation we would have defined the term floods, and described the types of floods such as riverine, coastal, flash and estuarine. A thorough explanation on the types of precipitation events, influence of human activity, sea level changes and the drainage basin characteristics were done. The presentation also included the consequences and effects of floods. Last but not least ways to mitigate the effects of floods were discussed.