Internal Processes And External Forcing

The essay seeks to discuss the comparative role of, by use of examples the internal processes and external forcing on the environment and therefore propose conditions, actions and responses to address environmental changes. As examples floods and volcanic eruptions will be looked into.

Floods

Floods are defined as too much water that is usually not likely to be in a certain area, and that area is usually dry. It generally develops over a period of time sometimes due to heavy rains over a short period. Floods are natural events that could have great effects on people and the environment (C A Dosewell III, 2003). Floods are said to be among the most devastating natural disasters in the world, claiming more lives and causing more property damage than any other natural phenomena. They are becoming too frequent and are a threat to sustainable development causing consequences all over the world. “Climate change resulting from global warming is attributed to anthropogenic influences, leading to many consequences, one of which is flooding” (Magami I. M. , 2014).

Causes natural

It has been identified that floods are caused by a variety of climatic and nonclimatic processes that result in different types of floods. Floods may come about due to heavy rainfall that is sometimes sudden and lasting for a short period or sometimes rainfall that continues for days or even months. Tsunamis are described as high, large waves that typically are caused by undersea earthquakes, volcanic eruptions or massive explosions, these waves then cause sea water level to rise and overflow into buildings that are close to the sea and even beyond. Flood can also be caused by a rise through the melting of snowfall. In areas where the preceding winter’s snow pack is deep, a sudden change to warm temperatures in the spring can result in abnormally rapid melting and runoff of the snowmelt (Magami I. M. , 2014).

Human (UNESCO, 2018)

Defines the Anthropocene as the impacts of increased accumulation of greenhouse gases on climate and biodiversity and also the irreversible damage caused by over consumption of natural resources. (C A Dosewell III, 2003) states that there is evidence that human activities are increasing the potential for floods. Population pressure and urbanization are one of the most influencing human instances that increase the risks of flooding. Too much population on a small piece of land can make it difficult to deal with the drainage management (Oladele, 2015). The rate of urbanization is seen as a contributing factor to flooding to a location for instance, a relatively small amount of rainfall can trigger flash flooding in a heavily urbanized region (C A Dosewell III, 2003). In agreement (Magami I. M. , 2014) says that urbanization can increase as much as two to six times water runoff over what would normally occur on natural terrain. Thus, unplanned urbanization is a flood risk. Urban floods can cause high economic damage to businesses and homes. Poorly planned, managed or constructed reservoirs also pose a risk to floods. Bursts water from main pipes and Dam failures that may be due to poor maintenance and management also can lead to flooding.

There can be even accidental floods that may be caused also by damage of tunnels or pipes in cities by workmen while attending to other projects. Sometimes people put themselves in difficult situation and in risks of being affected by flood, this can be through their stubbornness and negligence of warnings from the hydrological systems data. Development of flood-prone areas for habitation and recreation has been increasing, with a corresponding increase in the risks to life and property (C A Dosewell III, 2003). People also cut down trees which could be helping them against their properties being swept away and destroyed hence they increase the risks of being affected by floods. ” Vegetation works together with the soil to store rainfall, so when that vegetation is cleared, rainfall runoff can increase substantially. Rather than being absorbed by the soil and its natural vegetation, in areas where that vegetation has been cleared (either for construction or for agriculture), heavy rainfall is more likely to runoff and pour into streams and rivers, increasing the potential threat from flash floods and river floods” (C A Dosewell III, 2003) There is also a lack of flood control measures as people are not able to identify the necessary ways that will help control floods, such as building and clearing trenches so that when there is flood there will be water flow routes (Magami I. M. , 2014).

Types

Different types of floods have been identified by many authors. (C A Dosewell III, 2003) has described the flash floods as those flood events where the rise in water is either during or within a few hours of the rainfall, they are said to occur within small catchments, where the response time of the drainage basin is short. In contrast to flash flood river floods are said to unfold over days or months since they occur in large basins involving ‘main stem’ river. Usually they are a result of many individual rainfall episodes spread out over many days. Besides rainfall the river flood potential can be caused by concurrent snow melt. I addition (Magami I. M. , 2014) noted that flash floods give a minimal time of warning with rapid and significance rise of water level due to intense heavy rains. They also stated that flash floods can also occur due to a dam or levee failure. River floods are caused when water runoff gets collected in rivers or streams eventually reaching limits and overflowing into banks. (Magami I. M. , 2014) went on to explain other types of floods such as the coastal floods which occur when ocean water is pushed inland. Coastal flooding can be caused by hurricanes and tropical storms that cause large waves that lead to rise in sea level then causes overflow into the beaches. Earthquake also displaces large amounts of water causing waves called tsunamis to rush inland.

Cases in botswana

Botswana has also had its fair share of experiencing floods, it has been affected by floods since long ago and is still experiencing this tragic event. Due to heavy rainfalls, flooding occurs mostly in the North-West, North-East, and parts of Central district of Botswana. Between 16-23 Jan 2013, it was discussed that heavy rains caused extensive flooding in the Central District of Botswana. At least 842 families (4,210 persons) were affected. The torrential rains destroyed homes, roads, flooded dams, fields and destroyed livestock and livelihoods (Oladele, 2015). Floods have been experienced in Botswana at the Okavango in 2009 which was exceeded during the 2010 annual flood when villagers were displaced. Flash floods have struck the Ngamiland district at the beginning part of the Okavango delta. In June 2009 heavy rains flooded seven villages in central Botswana and over 4000 inhabitants were displaced (Kgosietsile Maripe, 2016). With the most recent floods, between 18 and 23 February 2017, Botswana was hit by the tropical depression, ex-Dineo which caused significant flooding across the country (International Federation of Red Cross & Red Cresent Societies, 2017).

Effects

Negative

Climate change has brought about a great change in rainfall pattern thus increasing flood risks in many cities. Water logging also generates difficult challenges for hydrologist because of the strong intensity of the natural disaster. Floods are a threat to human beings in many different ways including loss of lives and personal property, among others. Their effects on the environment can also include damage to infrastructure (roads, buildings, dams and bridges) and damage to vegetation (crop fields and natural vegetation) (STATISTICS BOTSWANA, 2016). Many farmlands both arable and agro-forestry may be swept away, this therefore leading to sudden food shortage resulting from loss of entire harvest, spoiling of grains when submerged in water along with loss of animal fodder.

Some animals may lose their lives to flooding due to drowning, catching cold or even not getting food as they would have been wiped away by the flood. Many bridges can collapse with electric poles being destroyed while schools and other properties get submerged (Magami I. M. , 2014) The economy can also be severely affected by flooding. Loss of stock, investment, data and productivity and disruption to utilities and transport infrastructure can have knock-on effects to a wider area. Tourism, farming and livestock can equally be affected. Disrupts normal drainage systems posing health hazards. These include contamination of water supplies (water pollution). , clean drinking water therefore becomes scarce with consequent unhygienic conditions and Spread of water-borne diseases.

There will also be disruption in transport as most vehicles will be damaged, roads will be left in bad state and people may fear that their cars will be affected by bad roads therefore will avoid using them and as a result there will be reduced transport accessibility (Magami I. M. , 2014). Positive Even though flooding is a disaster to human it may prove to be of important to the environment because when left in its natural state it has been said that the benefit of floods outweigh their adverse effects to the environment, it is also part of the natural processes shaping the Earth. Floodplains along rivers and streams are among the most fertile regions known that is the reason people are still being found living along flood prone areas, it is a source of their livelihood they plough along these flood prone areas.

Actions

There has to be collaboration and coordination by all countries to come up with ways measures that could work towards reducing human impact on the environment and therefore climate change, such as sustainable development and livelihood goals. Governments could improve and ensure proper management and maintenance of drainage systems and water flow channels. There should be a review of reports made by previous researches (especially of recent) on Floods Risk Management (FRM), Integrated Flood Management (IFM), Flood Control measures, causes of flood, consequences of floods, Flood Mitigation, Flood Evacuation Methods, whether those reports were made by NGOs, Water Ministries, Environmental Agencies, Research Institutes or even individual researchers. Government can then look into the possibilities of implementing the necessary measures among them (Magami I. M. , 2014).

Volcanic eruptions

Volcanoes are huge underground eruptions that emerge on the earth surface. Large, explosive volcanic eruptions have been known to affect climate significantly. According to (Allegra N. LeGrande and Kevin J. Anchukaitis, 2015) volcanic eruptions are identified as some of the most climatically important and societally disruptive short-term events in human history. When these volcanoes erupt they emit gas and ashes to the environment which bring about change into the environment and climate as well. The ash, dust and smoke produced by the from the volcanic eruptions partially block the transmission of solar radiation to the Earth surface for long periods, months or even years, and cause a cooling of temperatures. In describing the gases emitted by volcanoes (Alan Robock, 2000) states that large eruptions emit ash, dust, gases such as sulfurous gases (e. g. SO2, H2S), halogens (e. g. HCl and HBr), and water vapor into the Earth's atmosphere. Sulfurous emissions principally interact with the climate by converting into sulfate aerosols that reduce incoming solar radiation, this then warms the stratosphere and alters ozone creation, reducing global mean surface temperature, and overwhelming the hydrological cycle. Volcanic eruptions are said to cause large inter-annual to decadal-scale changes in climate. It has been identified that the cooling effect caused crops to shrivel and therefore produced famine. It is stated that Benjamin franklin suggested that Lakagiger eruption in Iceland in 1783 may have caused the summer to be cold in Europe in the same year and the following one.

Volcanic eruptions affect societal systems as well, agriculture and infrastructure can be intensely disturbed by these severe short-term geological and climate events, even at places quite distant from the eruptions themselves. Volcanic aerosol consists mainly of concentrated sulfuric acid (75% H2SO4 ), although the bulk of the erupted volcanic material consists of large ash particles which fall out rapidly, leaving the sulfur bearing gases to form the more enduring volcanic aerosol. It is this longer lasting aerosol that causes cooling of the global surface temperature (solar albedo effect), and warming of the lower stratosphere (greenhouse effect) (Allegra N. LeGrande and Kevin J. Anchukaitis, 2015). According to (Alan Robock, 2000) The most obvious and well-known effect of volcanic eruptions is on solar radiation. It is said that the “sulfate aerosol particles are about the same size as visible light, with a typical effective radius of 0. 5 mm, but have a single scatter albedo of 1, that is they strongly interact with solar radiation by scattering.

Some of the light is backscattered, reflecting sunlight back to space, increasing the net planetary albedo and reducing the amount of solar energy that reaches the Earth’s surface. This backscattering is said to be the dominant radiative effect at the surface and therefore results in a net cooling there”. Much of the solar radiation is forward scattered, thus resulting in enhanced downward diffuse radiation that somewhat compensates for a large reduction in the direct solar beam. The volcanic aerosols also serve as surfaces for heterogeneous chemical reactions that destroy stratospheric ozone, which lowers ultraviolet absorption and reduces the radiative heating in the lower stratosphere, but the net effect is still heating. The illustration below show volcanic inputs to the atmosphere and their effects. Volcanic soils also referred to as andisoils are known for their high levels of fertility. Land that is around volcanoes throughout the world is often heavily cultivated due to their fertility in order to reap the benefits from the natural fertilizing effects of terrestrial volcanic deposits (Lebon, 2009).

Conclution

Even though we tend to look adversely at the negative impacts of the internal processes and the external forcings there are also the positive effects. These processes are part of nature and in every event that takes place it is the earth reshaping itself, humans may be the ones who interfere with nature by their developments on the environment. This is mainly the reason people are always found living in disaster prone area, which is so that they can get the benefits provided by those areas. But with the internal processes such as the volcanic eruption there is really no contribution human can do to improve the situation as it is purely natural and human are not influential on them.