Flash Floods

Flash flooding is flooding that was not expected. Flash floods are the most dangerous of all floods because of the element of surprise. Intense rainfall over a significant period of time can cause flash flooding. The speed with which a flash flood can occur makes it even more dangerous. Flash floods often occur in dry areas where the ground is baked hard. When torrential rains do come, water immediately fills arroyos, or dry stream beds, turning them into raging rivers. The torrent of water rushes through with enough force to wash away sections of concrete road.

Flash flood waters move very quickly and can move boulders, tear out trees, and destroy bridges and buildings. Sometimes a wall of water 10 to 20 ft (3 to 6 m) high carries a huge amount of debris. The worst flash floods are created when a dam or levee breaks and a huge amount of water suddenly pours downstream, destroying everything in its path. Inland flooding has been the number-one cause of deaths from hurricanes in the past 30 years. In 1999, Hurricane Floyd caused 56 deaths. Fifty of them were people who drowned due to inland flooding. Inland flooding occurs when a slow-moving storm is accompanied by heavy rains. Inland flooding is a threat to communities hundreds of miles from the coast. Over a third of the people who drown during an inland flood are in their cars. Some are trying to escape the flooding, while others are attempting to abandon the cars. Even a foot of water can cause a car to float, and if that water is rushing down a street, the car can be swept away.

All kinds of floods cause problems for people. The worst consequence of floods is loss of lives. Property damage is a major problem with flooding. Houses can be completely demolished or even carried away down a turbulent river. Even houses left standing after a flood usually have substantial water damage and some have structural damage as well. Also, when the water subsides, it leaves behind a thick, sticky coat of mud filled with debris. So even if there is no structural damage, cleaning up after a flood is a big job.

Floods can also spread disease. Water flowing through an area can pick up chemicals and waste products and move them to another place. Most diseases are more easily spread through water than through air. That is one reason it is so important for those in a flooded area to drink only bottled or boiled water. Besides damaging homes, floods can cause other problems to agricultural areas. Soil can be eroded and crops already in the fields can be ruined. Floods also damage reservoirs and rivers where they deposit the load of soil the water picked up from the fields.

Floods

OF ALL THE NATURAL hazards in the world, floods are the most widespread. Historically, floods have killed more people and caused more damage than any other type of natural disaster. A flood is defined as an overflowing of water on an area that is normally dry. There are several types of flooding, including river flooding, coastal flooding, urban flooding, inland flooding from hurricanes, and flash flooding. Each has its own causes and characteristics, but all can be deadly and floods can happen anywhere.

Throughout history, people have always built their towns and cities near water, both along the seacoast and along rivers further inland. The water serves many purposes. It is used for drinking, cooking, and bathing. Water in many places has been used as a source of power, to turn wheels that grind grain. Running water is similarly used to create hydroelectric power. Another reason for settling close to water is that it has always been an easy way to travel and to transport goods. The disadvantage of living near water is the possibility of flooding.

The amount of water on Earth is fairly constant all the time. Each day, some of the water on the Earth is lost into the atmosphere through the process of evaporation. Water in rivers, lakes, and oceans is always evaporating at a slow rate. Most water on the Earth is in the form of liquid, but at the poles we find water in its solid or ice form. Water in glaciers is also in the form of ice.

At some places, water is in the form of water vapor in the air. This is the water that has evaporated from the surface of a body of water. A water molecule remains in the atmosphere for approximately 9 or 10 days before it falls as rain or snow. This happens when the amount of water in a cloud becomes heavy enough to form drops of water, which then fall to Earth. Rain that goes into the bodies of water begins the cycle again. Some rain will soak into the ground, where it will spend some time as groundwater.

River flooding is one of the most common types of flooding. It occurs when rainfall throughout the year is unevenly distributed. Too much rain goes into the river at one time and the water exceeds the capacity of the channel. When that happens, the stream will overflow its banks. Another cause of river flooding is melting snow in the spring. In areas with hills or mountains, the snow in the higher elevations melts and the water runs down into the streams. If the snowfall was heavier than usual, floods may occur. Also, spring rains often occur at the same time as the snow is melting, contributing more water to the streams and rivers. The torrential rains that accompany a hurricane or other tropical storm can also cause flooding in rivers.When heavy rains fall on bare soil, it is churned into mud. This keeps the water from soaking into the ground, and most of it will flow across the surface of the ground, creating gullies leading to rivers and streams.

Coastal flooding occurs when ocean water is driven inland by winds from tropical storms or hurricanes. Sometimes escape routes are blocked by this high water and people cannot escape. Coastal flooding can also be caused by a tsunami, which is a sea wave sometimes referred to as a tidal wave. These huge waves are caused by volcanic activity or an earthquake. When urban flooding occurs, the streets in a town become swift rivers and basements fill with water. This is partly due to the fact that land that used to be fields or woodlands has been converted to roads and parking lots. The concrete or asphalt cannot absorb any rainfall and it runs off the surfaces of the parking lots and roads.

Floodplain

FLOODPLAINS HAVE been a focal point of settlement throughout history and of controversy in recent decades. Humans are drawn to floodplains to cultivate the fertile soils that compose them. Floodplains are some of the best lands for growing crops, but they come with a price. Sometimes, rivers exit their banks and inundate the flat lands and everything on them.

A floodplain is defined as a strip of relatively smooth land bordering a stream that overflows at time of high water. Floods build up the bordering plains with organic-rich sediments. While flooding is sometimes disastrous for humans, it is necessary in the development of floodplains. Rivers create floodplains over thousands of years through two processes, vertical and lateral accretion.

Vertical accretion is the deposition of sediments like sand, silt, and clay from floodwaters. As floodwater spreads out over a flood plain, it slows down and loses energy. As energy is lost, sediments held in suspension drop out and are deposited on the plain. The heaviest sediments, like sand, are the first to be deposited and accumulate near the river channel to form a natural levee. Lighter sediments, like clay, stay in suspension longer and are deposited further away from the river in areas called back marshes.

Lateral accretion is the deposition of sediments to the inside curve of river meanders. As water flows around a curve, the current is fastest on the outside and erodes sediments to create a cut bank. The current on the inside of the curve is of low energy and suspended materials drop out. In this way, point bars are created as the river moves laterally. Because of this, land on one side of the river may be much younger than that of the other.

Today, natural floodplain processes have been largely interrupted in the UNITED STATES. Large networks of artificial levees have been constructed to protect crops and property from flood damage along many of the country’s rivers. While flooding is decreased, so is the natural fertilization of soils. Thus, farmers have to apply artificial fertilizers to sustain crop yields, adding to pollution.

The effectiveness of flood control levees is now being questioned. While flooding has been decreased, it is becoming apparent that the severity of floods that do occur is being increased. As more levees are built, less floodplain area is available for rivers to spread over; this means that more water is confined between the levees.

When a levee is breached during times of high water, the result is massive local flooding rather than normal flooding over a broad expanse. Steps are now being taken to curb the flooding problem. Floodplain lands are being purchased and returned to their natural cycles. This effort relieves pressure between the remaining levees and lessens the necessity to continually increase the height of levees.

Finland

AS CITIZENS OF the northernmost country in Europe, the people of Finland have long experienced the effects of their nation’s absolute and relative location. Finland spans approximately 690 mi (1,104 km) from the 60th parallel in the south to the 70th parallel in the north with approximately one-third of the country falling above of the ARCTIC CIRCLE. While the climate of Finland is moderated by the effects of the Baltic Sea, it is nonetheless greatly determined by its high latitude. The mean annual temperature of its capital, Helsinki, is only 41 degrees F (5.3 degrees C) with an average July temperature of 62 degrees F (17 degrees C) and February temperature of 22 degrees F (-5.7 degrees C).

The physical geography of Finland has also been greatly shaped by its absolute location as a result of continental glaciation that once covered large portions of northern Europe. As the ice advanced and retreated across the landscape, it carved the southeastern portion of Finland into a patchwork of shallow lakes, giving Finland’s its nickname, Land of a Million Lakes. The movement of ice sheets was never constant, and in their retreat they remained stationary three times, depositing rock and sediment debris to form moraines and drumlins. Stream flow beneath the glaciers deposited additional material, thereby forming ESKERs that stretch from east to west across the country and are called the Salpauselkä ranges. With the retreat of the ice approximately 12,000 years ago, the land itself reemerged from the sea, freed from the immense weight of the glaciers. This process continues today, with the land area of Finland increasing by approximately 2.7 square mi (7 square km) annually.

The postglacial landscape combined with the high latitude provide the basis for a natural environment predominated by boreal forests in the south and lowlying scrub vegetation in the northern reaches of Lapland. As a natural resource, the forests of Finland play a significant role in the economy of the nation with the development of lumber and paper industries. With significant governmental intervention in the 20th century, the Finnish wood industries have worked to increase timber harvests while conserving forested land in the interest of recreation and other nonindustrial uses.

The forests have also been long associated with the development of Finnish culture. Although Finnish society first developed with agriculture, the forests continued to represent a store of wealth for the inhabitants with their abundant flora and fauna. The natural resources of Finland also caught the attention of growing European empires. With the expansions of the Vikings eastward toward RUSSIA, the people of Finland were eventually incorporated into the Kingdom of SWEDEN and converted from their preexisting pagan beliefs to Roman Catholicism. With the development of the Great Schism and eventual adoption of Orthodox Christianity in Russia, Finland became a religious and imperial battleground between East and West. For approximately 800 years, the majority of contemporary Finland remained within the domain of the Kingdom of Sweden, even converting to Christian Protestantism with the arrival of the Reformation. But after multiple wars and several tenuous periods of peace throughout those centuries, control of Finland was transferred to the Russian empire in 1809.

As an autonomous grand duchy under the control of the Russian tzar, Finnish governmental organization remained relatively unchanged and experienced, at least for a brief span of time, an unprecedented period of peace free from the wars that had plagued its people for centuries. With the demise of the Russian Empire in 1917, Finland sought its own independence and the Republic of Finland was declared. The transition to independence was not without conflict, however, and the people of Finland were embroiled within a civil war between the Reds and the Whites, both of which sought control of the new nation. Less than 20 years later, Finland was once again engaged in conflict, this time caught in the power struggle between GERMANY and the Soviet Union in World War II. The conclusion of the war ultimately resulted in the loss of eastern Finnish territory in the region of Karelia to the Soviet Union.

Hemisphere

THE WORD hemisphere means “half a sphere.” In geography, the term refers to half the Earth, and the enclosing boundary line of a hemisphere is a great circle. A space traveler viewing the Earth from a great distance will see only half the earth, a hemispheric perspective. This is true because the Earth is a sphere and only one side of the Earth can be seen in any one particular view.

Our only look at the entirety of the Earth’s surface is through world maps. The map view of the world is important for that reason despite the fact that every is a scaled-down replica of the Earth, 2) presents a generalized view of the Earth’s surface, and 3) is a distortion of the Earth’s surface to varying degrees.

There are an infinite number of possible hemispheric views of the Earth. When an observer looks directly at any particular point on the Earth’s surface, a hemisphere is defined. However, there are a number of hemispheres that have special importance for the discriminating viewer. For instance, if the equator is the great circle enclosing a hemisphere, the viewer will be seeing either the Northern Hemisphere or the Southern Hemisphere. In both cases, the center of the hemispheric view will be one of the poles. Viewing the Southern Hemisphere would show vast expanses of the southern oceans, interrupted by the southern extremes of South America and Africa, about half of AUSTRALIA, all of NEW ZEALAND, and a few scattered islands in the PACIFIC OCEAN. In the center of the view would be the geographical South Pole and the continent of ANTARCTICA, a true landmass covered by heavy sheets of ice.

For example, South Pole station sits on ice that measures 8,000 ft (2,438 m) in thickness. The presence of a preponderance of water in the Southern Hemisphere has a great impact of the climate in this region. Since large water bodies do not heat up and cool as quickly as comparably sized land areas, the annual changes in temperature are much lower.

The view of the Northern Hemisphere is distinctly different. At the center of the view is the geographical North Pole, a point that is impossible to permanently mark on the surface because of the constant movement of the ice on the Arctic Ocean. South of the pole are the northern regions of the great landmasses of the northern hemisphere. Particularly imposing in this regard is the longitudinal sweep of Eurasia extending over 180 degrees of longitude. RUSSIA alone boasts of having 11 time zones. The northernmost reaches of North America are also prominent in this view, its land area bracketed by the ATLANTIC and PACIFIC oceans. The climatic impact of the presence of large land areas in the Northern Hemisphere is profound. The variability in annual temperatures is extreme in this region. It is not uncommon for areas within the continents of Eurasia and North America to have average winter temperature near 0 degrees F (-17.7 degrees C) and summer averages in the 70 and 80 degrees F (21 to 26 degrees C) range, temperature ranges not found in the southern hemisphere.

Familiar to everyone are the Eastern and Western Hemispheres. The two are separated by a great circle comprising two longitude lines, both running from pole to pole in opposite directions. The longitude line designated 0 degrees passes through Greenwich, England, and serves as one of the dividers between the two hemispheres. Its counterpart passes through the Pacific Ocean 180 degrees from the prime meridian. Hence, it is identified as longitude 180 degrees. An observer standing at any location along either of these lines is on the boundary between the eastern and western hemispheres. The prime meridian is the conventional starting point for assigning degree values to longitude lines.

Wind Energy

As moving air, wind is a nondepleting source of renewable energy. Wind can be of devastating power. Storms and hurricanes are proof of strong winds having the power to uproot trees and destroy homes and other infrastructure. That wind power can be used as a source of energy has long been known to humanity. The utilization of wind energy is not a new technology; the generation of electricity from wind power took place many years ago. Electricity generation (energy conversion) from fossil fuels is largely contributing to greenhouse gas (GHG) emissions, primarily carbon dioxide (CO2), which have been identified as the main driver of global warming and climate change. Wind is a clean energy source with the potential to replace other polluting, electricitygeneration technologies.

How much energy the wind is carrying depends on several factors: the amount of wind energy flowing through a given area, or area swept by a turbine (A) during a fixed time; the time to pass the turbine (t); the wind’s velocity before the turbine (v); and its density (ρ). The wind’s kinetic energy (Ekin) is calculated using the formula: Ekin = ρ/2 A v3 t. The wind speed (v) is normally measured in meters per second (m/s) using an anemometer (wind speed meter). Practical wind power density (WPD) maps are established to provide the mean annual power available per sq. m of swept area of a turbine for different heights in watts per square meter (W/m2) and serve as a reference as to the best location to install and operate wind turbines.

Wind is produced by differences in air pressure, which are the result of the unequal heating of the Earth’s surface by the sun (which in turn heats the air above it). This unequal heating of the Earth’s surface is the result of the difference between outgoing and incoming radiation at high and low latitudes of the Earth, which rotates around a shifted axis. Heated air expands and decreases in density.

Following the second law of thermodynamics, the air then flows from areas of high pressure to areas of low pressure until the air pressure is balanced (and the entropy is maximized). The higher the pressure difference and gradient, the stronger the wind that seeks to balance the difference. Because the Earth is rotating, the angular momentum is conserved with the wind, which is shifted along a longitudinal direction resembling a circular movement (Coriolis effect). On a local scale, the geographic and topographic properties of the Earth’s surface largely influence how uniformly and consistently the wind is flowing.

Offshore and onshore winds are generated along the shores of large lakes and ocean beaches. Those winds blow very regularly as they are created by the different heat absorption and storage properties of the land and water surfaces. Likewise, mountain-valley breezes arise from the unequal heating properties of the mountain-valley topography. Surface wind speeds tend to be lower when the movement of air is obstructed by geographical features, vegetation, or buildings. Therefore, coastal and offshore sites are ideal locations for wind-turbine installations.

Solar Thermal Technologies

Solar thermal technologies convert incoming solar radiation into thermal energy for heating or cooling applications. A solar water-heating system is an example of solar thermal technology. Solar energy collectors, in the form of flat plates or evacuated tube collectors, convert solar energy into heat. Heat from the collectors is used to heat the water. In low geographic latitudes, residential hot water temperatures can reach 140 degrees F (60 degrees C) with such solar heating systems. In a similar vein, solar concentrating technologies, using parabolic dish or parabolic trough reflectors, can greatly increase the temperature of a small solar collection area. Heated fluid at much higher temperatures can be used for industrial process heating.

Concentrated solar power (CSP) systems are large-scale, solar thermal energy technologies. CSP systems use large arrays of lenses or mirrors and advanced solar tracking systems to focus a large area of sunlight onto a small area. This concentrated heat is used as the heat source for a conventional power plant to generate electricity.

Solar energy can also be used in the water treatment process. Solar distillation technologies use the thermal energy from sunlight to evaporate saline water. By condensing and collecting the evaporated water, brackish water can be made potable. Similarly, solar water disinfection (SODIS) is a solar energy technology for water pasteurization. By placing polyethylene terephthalate (PET) bottles filled with water in sunlight, the water temperature increases to the pasteurization temperature, thereby killing organic pathogens and resulting in safe drinking water.

Passive solar thermal energy technologies can also be used to offset a portion of the energy required for building heating, ventilation, air conditioning, and lighting systems. Proper building design can allow for solar heating of a thermal mass to store heat. This stored thermal energy is released slowly to regulate, maintain, and offset the building’s heating requirements. Similarly, proper shading techniques, such as the use of deciduous trees and building overhangs, can reduce a building’s heat gain and cooling load.

Passive solar ventilation systems or solar chimneys can be utilized to offset ventilation costs. As the chimney warms when exposed to solar radiation, the temperature of the air inside the chimney increases, creating an updraft that moves cooler air through the building.

Solar Energy Use

Currently, over 40 gigawatts (GW) of power are generated from solar PVs worldwide. Overall, the use of renewable solar energy technologies represents a small fraction of the total energy production worldwide. A primary obstacle to increased solar energy technology deployment is the high initial investment cost. Because of the high availability and relatively low cost of fossil fuel energy sources, the economic rewards for typical solar thermal energy technologies, such as domestic hot water heating, range from approximately 3 to 20 years depending upon the size of the installation and solar energy availability. 

Small scale, solar PV installations currently require from approximately 5 to more than 30 years for the economic gain to be realized. Such large initial capital expenditures and long repayment periods significantly reduce the incentives to implement this technology. As the cost of fossil fuels increases, government incentives for renewable energy technologies increase, and as the conversion efficiencies for solar energy technologies improve, such economic barriers to installation may decrease.