Study Session 10  Extreme Weather Events

Introduction

You often hear on the radio and TV or in the newspapers that extreme weather events such as floods, storms and typhoons have affected hundreds of people and damaged buildings, water supplies and sanitation facilities. Extreme weather events are expected to increase in the future because of climate change. Knowing what extreme weather events occur in Ethiopia can help WASH workers plan and prepare to reduce the impacts.

In this study session you will look at what is meant by the term ‘extreme weather’ and learn about three types of extreme weather event that occur in Ethiopia: floods, droughts and heatwaves, and also about wildfires, which are not themselves weather events but are associated with very dry weather. Our focus in this study session is on the impact of these events on the environment and on WASH services. The impacts on human health, agriculture and the economy in Ethiopia are discussed in Study Session 11.

Learning Outcomes for Study Session 10

When you have studied this session, you should be able to:

10.1 Define and use correctly all of the key words printed in bold. (SAQ 10.1)

10.2 Describe the main types of extreme weather events in Ethiopia and how they affect the environment. (SAQs 10.1, 10.2 and 10.4)

10.3 Explain how natural climate cycles and human activities can increase the risk of extreme weather events in Ethiopia. (SAQs 10.2 and 10.3)

10.4 Describe how extreme weather events can affect WASH in Ethiopia, including in urban areas. (SAQs 10.3 and 10.4)

10.1  What is extreme weather?

You know from your own experience that the weather varies from day to day, month to month and year to year. Most of the time, these fluctuations occur within a normal range. Some periods are hotter, colder or wetter than others, but these variations are not unusual. Extreme weather events are periods of weather outside the normal range of weather conditions. For example, floods that happen because of excessively high rainfall, or droughts, or heatwaves and wildfires resulting from a period of unusually high temperature, are extreme weather events.

We expect certain weather in different regions of Ethiopia – hot and dry in the lowland areas, but cooler and wetter in the highlands. We expect some areas to flood and some areas to have drought from time to time. But if the weather conditions are extreme, then we have unexpected conditions to deal with. Study Session 9 concluded that low-income countries like Ethiopia generally lack the personnel, equipment, infrastructure and finances to deal with the effects of climate change and increasingly frequent extreme weather events.

Globally, there are many types of extreme weather events, but we will focus on floods, droughts, heatwaves and wildfires because they are the most likely to affect Ethiopia.

10.2  Floods

Floods are extreme weather events that have had major effects in Ethiopia at different times and in different locations. In recent decades, major floods outside the normal pattern of flooding have occurred in Ethiopia with increasing frequency (EM-DAT, n.d.). They have been responsible for many deaths of people and livestock, and caused damage to homes (Figure 10.1), livelihoods and infrastructure in many parts of the country (MoWR/NMA, 2007). Table 10.1 shows the costs of major flood events in 2005 and 2006, which were the worst in recent years in terms of deaths and economic damage in Ethiopia.

Figure 10.1  Homes damaged by the 2006 flood in Gambela town, Ethiopia.

There are two main types of floods – flash floods and river floods – both of which affect water supply and sanitation.

10.2.1  Flash floods and their causes

Flash floods are floods that happen as a result of intense rainfall in a localised area and they usually drain away quite quickly (Few, 2006). If a large amount of rain falls onto the land in a short time and it cannot soak into (infiltrate) the soil, the water runs downhill across the land surface. This heavy flow of surface run-off can cause a flash flood.

There are many factors that increase the risk of flash floods in Ethiopia, including changes in land use and poor soil permeability (Abaya et al., 2009). As you read in Study Session 6, when forests and grasslands are removed for the construction of roads and buildings, permeable soil is replacedby hard surfaces such as concrete. This reduces the infiltration of water into the ground and increases run-off,making flooding more likely. The proportion of Ethiopia’s land area that is covered by forests has decreased significantly in recent decades, as Study Session 1 demonstrated (see Figure 1.3).

Failures of dams and reservoirs can also lead to flash floods. Many micro-dams have been constructed in Ethiopia for irrigation, water supply and generating hydroelectric power. Dam failure can occur if they are not properly constructed, or heavy rainfall may cause ‘overtopping’ (water flowing over the top of the dam when it is full).

Flash flooding has happened many times, in many parts of Ethiopia. This causes significant harm to human life and property because it happens so unexpectedly and local people are unprepared (Greenough et al., 2001). For example, the flash flood on 5 August 2006 in Dire Dawa caused 256 deaths and displaced 9956 people (Early Warning Department, Federal Disaster Prevention and Preparedness Agency, 2007).

10.2.2  River floods and their causes

River floods occur when the water level rises and water spills over the top of the river banks. The overflow runs into nearby low-lying areas, where it collects as flood water (Douben, 2006). River floods in Ethiopia generally occur because of intense heavy rain at high altitudes, which results in water flowing down into lowland rivers, which then burst their banks. Unlike flash floods, river floods tend to build up slowly, but they remain for much longer periods. Figure 10.2 shows river floods in Dire Dawa and Gambela.

Figure 10.2  Floods in (a) DireDawa and (b) Gambela in 2006, resulting from the overflow of the Dechatu and Gambela rivers respectively.

Figure 10.3  Flood-prone areas in Ethiopia. Areas shaded in the darkest colour are at the greatest risk of flooding. (EDRI/GGGI, 2015)

The impacts of river floods depend on many factors, such as the presence of early warning systems (Bonacci and Ljubenkov, 2008). There is no effective early warning system in place in most flood-prone areas of Ethiopia, but rural communities can reduce the impact, for example by moving livestock to higher ground at the start of the flood season. But this precaution is only effective for the normal intensity and frequency of floods – it cannot deal with unusually extreme flooding – and people in urban communities are usually unable to take any action to avoid flood damage.

The severity of flooding is increased by the absence of vegetation, intensive farming methods and deforestation, all of which increase soil erosion. Bare soil is more easily washed away by heavy rain than soil that is held together by the roots of trees and other plants. Soil erosion is the main cause of increased amounts of sediment in many Ethiopian reservoirs. As soil is washed off the land into the reservoir, sediment builds up behind the dam and it can significantly reduce the reservoir capacity, leaving the dam less able to withstand a major flood.

10.2.3  The impact of floods on WASH in Ethiopia

Floods often cause major damage to basic facilities such as water supplies, sanitation, waste disposal systems and other essential services. This poses a serious challenge to public health. Excessive rain and flooding can create conditions that increase the spread of faecal-oral diseases because flood waters flush pathogens and pollutants into water supplies from flooded latrines and places used for open defecation.

As well as polluting water sources, floods also can damage shallow wells, boreholes fitted with windmills, and protected springs, and they can wash away water pipes (Ethiopia Red Cross/Red Crescent, 2005). The result is that people are unable to access safe drinking water unless temporary water supplies can be provided (Figure 10.4).

Figure 10.4  Children fetch water from a water point constructed after flooding by the Lutheran World Federations.

10.3  Drought

Drought is not a new word to many Ethiopians. Drought is the absence of rain for an extended period, often for a season or more. Climate change is associated with the significant reduction in rainfall and increase in droughts that is already apparent in some parts of Ethiopia. Droughts have caused loss of human life, livestock and property, as well as migration of people (MoWR/NMA, 2007).

More than 85% of the population of Ethiopia are farmers. Most of the agriculture in the country is small scale and therefore highly dependent on rainfall and traditional technologies. Drought affects agriculture by damaging crops and decreasing crop yield (Figure 10.5), which causes food shortages not only in rural areas but also in towns and cities. In the worst periods of drought there may be widespread famine, when the extreme shortage of food results in many deaths. The drought that occurred in 1984, leading to a famine that killed more than one million people, is still fresh in the memories of many Ethiopians.

Figure 10.5  Crop failure due to drought in Ethiopia.

10.3.1  How many Ethiopians are affected by drought?

More than 57 million people across Ethiopia have been affected by droughts since 1980 (MoWR/NMA, 2007). Table 10.2 shows the frequency and impacts of droughts between 1964 and 2003.

Even though the population of Ethiopia has increased over the period from 1964 to 2003 (which could partly explain the increase in numbers affected), the later droughts covered larger areas of the country and were more severe. Currently more than 10 million people live in the drought-prone areas of Ethiopia shown in Figure 10.6.

Figure 10.6  Drought probability map of Ethiopia. (Adapted from MoWR/NMA, 2007)

10.3.2  The causes of drought in Ethiopia

Global warming and alterations in rainfall patterns are believed to be the underlying cause of the trend towards more frequent and more severe droughts in Ethiopia (MoWR/NMA, 2007).

There are many other interlinked factors that cause droughts in Ethiopia. Between 1950 and 2014, the population grew from 18.1 million to 96.5 million people, so there has been a rapidly increasing demand for water to meet their needs (Figure 10.7). The rising standard of living, economic growth and industrial development all increase water demand because they require more water for additional uses. Particularly in urban areas, the demand for piped water and flush toilets has increased because households aspire to achieve higher standards of hygiene and sanitation.

Figure 10.7  Queuing for water near Moyale in Oromia Region, one of the worst-affected areas in the 2011 drought.

Population pressure also leads to high deforestation for agricultural expansion and to meet the growing demand for wood (Figure 10.8) to burn as fuel and also for building fences and houses.

Figure 10.8  Collecting wood for use in construction and for fuel contributes to deforestation.

In summary, climate change leading to global warming and reduced rainfall, coupled with population pressure, deforestation and change in land use are all major factors in the increasing risk of drought in Ethiopia.

10.3.3  Impacts of drought on WASH in Ethiopia

As well as causing shortages of food and surface water, droughts have a significant effect on the availability of safe water resources. Drought causes water scarcity, so people are more likely to use unsafe water sources such as polluted rivers, streams and lakes. During times of water scarcity, people may save whatever water they can find for drinking and cooking, and stop using it for hygiene activities such as handwashing after defecation (Kovats et al., 2003). Drought can also increase the concentration of pathogenic organisms in rivers and lakes because the lower volume of water cannot dilute the contaminants to below the infectious dose (Kovats et al., 2003). We will discuss the impacts on human health in Study Session 11.

10.4  Heatwaves

Heatwaves are prolonged periods of unusually hot weather, which may or may not be accompanied by high humidity. The World Meteorological Organization definition of a heatwave is ‘when the daily maximum temperature on more than five consecutive days exceeds the average maximum temperature by 5 °C. The perception of a heatwave varies geographically because it is measured relative to the average temperature in that area. For example, weather that is experienced as normal heat in summertime in Gambela town would be considered a heatwave in Addis Ababa city, where the average summer temperature is much cooler.

Heatwaves are a big challenge in low-income countries like Ethiopia, because energy resources for cooling and air conditioning are often lacking. Heatwaves can cause adverse health effects and even death when severe dehydration of the body results from excessive sweating. It is very important to drink plenty of water during a heatwave to replace lost fluids. When heatwaves occur in areas of Ethiopia with water shortages, people cannot get enough water to drink or to cool themselves, so provision of an adequate and safe water supply is important to reduce the impacts on human health.

10.5  Wildfires

Nowadays wildfires are becoming increasingly common in the world because of frequent heatwaves and hot, dry conditions resulting from climate change. A forest fire is called a wildfire when it spreads very rapidly over a large area and is extremely difficult to bring under control (Figure 10.9). In many countries, including Ethiopia, the United States, Russia and Australia, wildfires are common during the dry season and especially in severe droughts. More than 200,000 hectares of forest are lost every year in Ethiopia because of fires (Kovats et al., 2003). Climate change is expected to increase the intensity and frequency of droughts in many parts of Ethiopia, increasing the risk of more severe and frequent forest fires.

Figure 10.9  Aerial view of burning vegetation in Bale region, Ethiopia.

Wildfires are dangerous because they spread so quickly, destroying large areas of forest, damaging buildings and infrastructure, and killing any people, livestock and wildlife that cannot escape. Wildfires also have effects on human health through the emission of pollutants such as ash, toxic gases, dusts and debris into the atmosphere. Respiratory problems like asthma andbronchitis are made much worse if the air quality is contaminated with these products of burning vegetation.

Wildfires can also severely affect water quality. When the debris and ash are washed away by rain, they enter water sources such as rivers, streams and wells. The water can become cloudy with ash, taste or smell smoky or earthy, and contain toxic chemicals from burnt wood, which in turn can have adverse health effects if used for drinking (Waskom et al., 2013).

10.6  El Niño and La Niña

We conclude this study session by mentioning two natural climate cycles that can affect the location and frequency of extreme weather events around the world, including in Ethiopia. The rise in sea temperature that we described in Study Session 9 has widespread effects on ocean currents, particularly in the Pacific Ocean (National Weather Service, 2006). When the Pacific Ocean is unusually warm, it generates a climate cycle known as El Niño (‘little boy’ in Spanish); when the ocean temperature is unusually cool, the climate cycle is called La Niña (‘little girl’). El Niño and La Niña have opposite effects on the climate. Even though both of these ocean currents occur far away from Ethiopia, they influence the route and speed of major airstreams and alter the pattern of rainfall around the world, so that some regions are wetter than average and others are drier (Waskom et al., 2013).

The effects of El Niño and La Niña in Ethiopia depend on which of our two rainy seasons they occur in. The belg season is from February to March and the kirmit season is from June to September. If El Niño occurs during belg, it can cause above-normal rainfall, whereas if La Niña occurs during belg, it causes below-normal rainfall (FAO, 2014). In contrast, if El Niño occurs during kirmit, it decreases the seasonal rainfall, whereas La Niña during kirmit increases rainfall above the normal level (National Weather Service, 2006).

In the next study session, you will look in more detail at the impacts of climate change and extreme weather events on health, environments, agriculture, water resources and the Ethiopian economy.

Summary of Study Session 10

In Study Session 10, you have learned that:

1. Extreme weather is weather that departs from the normal range of climate conditions.
2. Floods, droughts, heatwaves and wildfires are the most common extreme weather events in Ethiopia.
3. Flash floods develop rapidly and are due to the run-off of intense rainfall collecting in a localised area, usually for a short time. River floods occur when the water level rises and spills over the river banks; the build-up is generally slower than in a flash flood, but the extent is greater and the duration is longer.
4. Floods cause major damage to basic facilities such as water supplies, sanitation and waste disposal systems; they contaminate water sources by flushing pathogens, soil and toxins into rivers, lakes, ponds and wells.
5. Drought is the absence of rain for extended periods, often for a season or more. The frequency of droughts has increased over time in Ethiopia.
6. There are many contributing factors to floods and droughts in Ethiopia, including population pressure, deforestation, climate change and the occurrence of natural climate cycles due to El Niño and La Niña currents in the Pacific Ocean.
7. Drought has a significant effect on water resources and WASH; it causes water scarcity which in turn may lead people to use unsafe water sources.
8. A heatwave occurs when the daily maximum temperature on more than five consecutive days exceeds the average maximum temperature by 5 °C.
9. Climate change is expected to increase the intensity and frequency of drought in many parts of Ethiopia, in turn causing more severe and frequent heatwaves and wildfires.
10. When debris and ash from the wildfires enter the atmosphere, they can cause respiratory problems; when they are washed into water sources by rain they can significantly reduce water quality.

Self-Assessment Questions (SAQs) for Study Session 10

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.