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Unit 5. Drainage Basin Geometry




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Exercises (A)

1. Learn new words:

quantitative – количественный law – закон

investigation – исследование, изучение to obtain – получать

geometric properties – геометрические basin order – порядок

свойства речного бассейна

fluvial morphometry – речная bifurcation ratio – бифур-

морфометрия кационное отношение

drainage basin – водосборный бассейн drainage density – густота

to propose – предлагать речной сети

tributary – приток to decrease – уменьшать

first order stream – река первого ряда

head of river – исток реки

examination – исследование

 

1. Translate the following word combinations:

the relationships between the various components of river systems; to

facilitate comparisons between basins; in recent years; the quantitative investigation of the geometric properties of rivers; to be called fluvial morphometry; for any drainage basin; a hierarchy of stream orders; to be originally proposed by; the amended systems of Shreve or Strahler; streams without tributaries; at the head of river systems; two first order streams; to make a third order stream; to be named from the highest order stream in the basin; the examination of a large number of systems; to be counted within each order; with increasing order in a regular manner; the law of stream numbers; similar straight-line plots; against the total stream lengths; law of stream lengths; an expression relating the number of streams; law of basin areas; in the next order; various geometric properties; downstream changes; to be regular and determinable; from the analysis of drainage basins; to be found on resistant rocks in the Appalachians; a measure of the texture of the drainage net.

Text (A)

Read the text «Drainage Basin Geometry»:



In order to understand more fully the relationships between the various components of river systems, and to facilitate comparisons between basins, geomorphologists in recent years have placed considerable emphasis on the quantitative investigation of the geometric properties of rivers and their basins. This type of analysis is called fluvial morphometry. For any drainage basin a hierarchy of stream orders can be applied. Although the idea was originally proposed by R. E. Horton, the amended systems of Shreve or Strahler are the ones generally used. Streams without tributaries at the head of river systems are designated first-order streams. Two first order streams join to make a third order stream, and so on. If a lower order unites with a higher order stream, the order of the latter remains unchanged. The basin order is named from the highest order stream in the basin.

The examination of a large number of systems has shown that if the number of streams is counted within each order, then that number decreases with increasing order in a regular manner. This is known as the law of stream numbers (Horton, 1945). Similar straight-line plots can be obtained if a stream order is plotted against the total stream lengths, per order (law of stream lenghts) (Horton, 1945) and against the total area drained by each order (law of basin areas) (Schumm, 1956). The bifurcation ratio is an expression relating the number of streams in a given order to the number in the next order. These various geometric properties show that in many river basins downstream changes are regular and determinable. The laws described above are known collectively as the laws of drainage composition.

Other useful indices that can be derived from the analysis of drainage basins include an index of drainage density (Horton, 1932), expressed as the total channel length divided by the total area of the basin. In the United States, wide ranges of density value occur: the lowest 2 to 2.5 km per square kilometer are found on resistant rocks in the Appalachians; values in excess of 200 are reported from badlands. Stream frequency is the number of channels per unit area: like drainage density, it is a measure of the texture of the drainage net.

Exercises (B)

1. Establish compliance between parts of sentences:

1. for any drainage basin 1. if a stream order is plotted

a hierarchy of stream orders against the total stream lengths

2. streams without tributaries per order

at the head of river systems 2. are regular and

3.the examination of a large number of determinable

systems has shown that if the number 3. are designated first-order

of streams is counted within each order streams

4. similar straight-line plots 4. can be applied

can be obtained 5. then that number decreases

5. the bifurcation ratio is an expression with increasing order in regular

relating the number of streams manner

6. these various geometric properties 6. in a given order to the number

show that in many river basins in the next order

downstream changes

 

 

Text (B)

Read the text «Speciality of drainage basin» using a dictionary:

A drainage basin is an extent or an area of land where surface water from rain, melting snow, or iceconverges to a single point at a lower elevation, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean. For example, a tributary stream of a brook that joins a small river is tributary of a larger river, which is thus part of a series of successively smaller area but higher elevation drainage basins. Similarly, the Missouri and American rivers are each part of their own drainage basins and that of the Mississippi River.

Other terms that are used to describe drainage basins are catchment, catchment area, catchment basin, drainage area, river basin, and water basin. In North America, the term watershed is commonly used to mean a drainage basin, though in other English-speaking countries, it is used only in its original sense, to mean a drainage divide, the one meaning an area, the other its high elevation perimeter of that area. Drainage basins drain into other drainage basins in a hierarchical pattern, with smaller sub-drainage basinscombining into larger drainage basins.

In closed ("endorheic") drainage basins the water converges to a single point inside the basin, known as asink, which may be a permanent lake, dry lake, or a point where surface water is lost underground. The drainage basin includes both the streams and rivers that convey the water as well as the land surfaces from which water drains into those channels, and is separated from adjacent basins by a drainage divide.

The drainage basin acts as a funnel by collecting all the water within the area covered by the basin and channelling it to a single point. Each drainage basin is separated topographically from adjacent basins by a perimeter, the drainage divide making up a succession of higher geographical features (such as aridge, hill or mountains) forming a barrier.

Drainage basins are similar but not identical to hydrologic units, which are drainage areas delineated so as to nest into a multi-level hierarchical drainage system. Hydrologic units are designed to allow multiple inlets, outlets, or sinks. In a strict sense, all drainage basins are hydrologic units but not all hydrologic units are drainage basins.

Unit 6. «Lakes»

Exercises (A)

1. Learn new words:

source – источник pond – пруд

feel into – питать glacial origin – ледниковое

stream – поток, течение происхождение

spring – родник destruction – разрушение

arid – сухой, засушливый to dam up – запруживать

saline – соленый humid – сырой

Dea Sea – Мертвое море depth – глубина

volcanic activity – вулканическая to prevent – предотвращать

активность runoff – сток

permanent – постоянный

ephemeral – переходящий

way – путь, способ

faulting – ошибочный прорыв,

разрыв в слове

crust – кора

crater – кратер

 

 

1. Translate the following word combinations:

а sizeable inland body; the source of the water; to fall into the lake; as rain or snow; by streams and springs; lakes without outlets; in arid regions; to be saline; result from weathering and volcanic activity; the concentration of salts; due to evaporation; some saline lakes; can be permanent or ephemeral; in cold regions; may be perennially frozen; faulting and gentle upwarping of the Earth's crust; to be responsible for some of the greatest lakes; upwarping formed Lake Victoria in Africa; the Caspian and Aral seas in Asia; to be formed by volcanic activity; to occupy craters and calderas; landslides form lakes by damming up valleys; especially in mountainous regions; lakes of glacial origin; to be far morenumerous than all other types;

to be located in glacially-formed bedrock basins; from the irregular deposition of till; ponds and small lakes; to extend below the water table; in many different ways; to occupy abandoned channels on floodplains; short-lived geological features; in humid regions; deposition of detrital sediments and of organic matter; to fill the basin; in arid regions; the exposition of chemical precipitates and sediments; to reduces the size of the lake.

.

Text (A)

Read the text «Lake»

Lake is а sizeable inland body of standing water. The source of the water is precipitation that falls into the lake as rain or snow, or is fed into it by streams and springs. Lakes without outlets are usually found in arid regions and tend to be saline; some, such as Great Salt I.ake and the Dead Sea, are more salty than an ocean. The salts in most saline lakes result from weathering and volcanic activity; they were carried into the lakes by water and wind, usually when the lakes were larger. The concentration of salts is due to evaporation. Some saline lakes, like the Caspian and Агаl seas, are landlocked arms of the ocean. Lakes can be permanent or ephemeral, and those in cold regions may be perennially frozen.

Lakes are formed in many ways. Faulting and gentle upwarping of the Earth's crust are responsible for some of the greatest lakes. Faulting produced those of the African Rift Уа11еу and of south-western United States. Upwarping formed Lake Victoria in Africa, and the Caspian and Aral seas in Asia. Lakes are also formed by volcanic activity, they occupy craters and calderas (as in Crater Lake, Oregon) and occur where lava flows and volcanoes obstruct drainage. Landslides form lakes by damming up valleys, especially in mountainous regions. А lake 70 km long and over 200 m deep was formed in 1840 when а landslide blocked the Indus River, Kashmir.

Lakes of glacial origin are far morenumerous than all other types put together. Some are dammed by ice, as in Greenland and in other regions now glaciated. Many are located in glacially-formed bedrock basins. Others result from the irregular deposition of till. Ponds and small lakes occur where kettle holes extend below the water table, as on Саре Cod, Mass. Rivers form lakes in many different ways, as, for example, the oxbow lakes that occupy abandoned channels on floodplains or the lakes found on deltas.

Lakes are short-lived geological features: their destruction commences as soon as they are formed. In humid regions the outlet stream lowers the barrier, and the deposition of detrital sediments and of organic matter helps fill the basin. In arid regions the Exposition of chemical precipitates and sediments borne by wind and stremas help fill the basin, and evaporation reduces the size of the lake.

 

Exercises (B)

1. Establish compliance between parts of sentences:

1. lake is а sizeable inland body 1. and the deposition of detrital

2. lakes are formed sediments and of organic matter

3. faulting and gentle upwarping helps fill the basin.

of the Earth's crust 2. as soon as they are formed

4. lakes of glacial origin 3 . of standing water

are far morenumerous than 4. are responsible for some

5. lakes are short-lived geological of the greatest lakes

features, their destruction commences 5. in many ways

6. in humid regions the outlet stream 6. all other types put together

lowers the barrier

 

Text (B)

Read the text «Distribution of lakes» using a dictionary:

The majority of lakes on Earth are fresh water, and most lie in the Northern Hemisphere at higher latitudes. Canada, with aderanged drainage system has an estimated 31,752 lakes larger than 3 square kilometres (1.2 sq mi) and an unknown total number of lakes, but is estimated to be at least 2 million. Finland has 187,888 lakes 500 square metres (5,400 sq ft) or larger, of which 56,000 are large (10,000 square metres (110,000 sq ft) or larger). Most lakes have at least one natural outflow in the form of a river or stream, which maintain a lake's average level by allowing the drainage of excess water. Some lakes do not have a natural outflow and lose water solely by evaporation or underground seepage or both. They are termed endorheic lakes.

Many lakes are artificial and are constructed for hydro-electric power generation, aesthetic purposes, recreational purposes, industrial use, agricultural use or domestic water supply.

Evidence of extraterrestrial lakes exists; "definitive evidence of lakes filled with methane" was announced by NASA as returned by the Cassini Probe observing the moon Titan, which orbits the planet Saturn.

Globally, lakes are greatly outnumbered by ponds: of an estimated 304 million standing water bodies worldwide, 91% are 1 hectare (2.5 acres) or less in area (see definition of ponds). Small lakes are also much more numerous than large lakes: in terms of area, one-third of the world's standing water is represented by lakes and ponds of 10 hectares (25 acres) or less. However, large lakes account for much of the area of standing water with 122 large lakes of 1,000 square kilometres (390 sq mi, 100,000 ha, 247,000 acres) or more representing about 29% of the total global area of standing inland water.

 

Exercises (B)

1. Сomplete the following sentences using suitable words and word-combinations given below:

artificial;stream;greatly; numerous; evaporation;drainage;at higher latitudes; ponds; fresh water; domestic; worldwide.

1. The majority of lakes on Earth are ………………., and most lie in the Northern Hemisphere ……………………... 2. Most lakes have at least one natural outflow in the form of a river or………………., which maintain a lake's average level by allowing the ………………of excess water. 3. Some lakes do not have a natural outflow and lose water solely by ………………..or underground seepage or both. 4.Many lakes are …………………and are constructed for hydro-electric power generation, aesthetic purposes, recreational purposes,industrial use, agricultural use or …………………water supply. 5. Globally, lakes are ……………outnumbered by ponds: of an estimated 304 million standing water bodies…………….., 91% are 1 hectare (2.5 acres) or less in area (see definition of ponds). 6. Small lakes are also much more ……………….than large lakes: in terms of area, one-third of the world's standing water is represented by lakes and …………………….of 10 hectares (25 acres) or less.

Unit 7 Flood

Exercises (A)

1. Learn new words:

bank берег according to – в соотвествии с чем-либо

to overflow – разливаться interval – промежуток, интервал

disaster– бедствие, несчастье recurrence interval – промежуток

fllod – наводнение, половодье, промежуток

разлив curve – кривая, диаграмма

beneficial result – положительный to measure – измерять

результат relatively – относительно

sediment – осадок level – уровень

to renew – обновлять, water surface – поверхность воды

восстанавливать to be expressed in быть

to fertilize – удобрять выраженым в чем-либо

to sink – просачиваться

soil – почва

to predict – предсказывать

magnitude – размер

frequency – частота

 

2. Translate the following word combinations:

the overbank discharge of а stream; on an average of every 1,2 years; as а disaster by man; on river floodplains; natural event; beneficial results; to deposit on the floodplain ; to renew and fertilize; to sink into the soil; to recharge the groundwater; а relatively high flow; to be measured by either gage height or discharge rate; indicate levels of the water surface; at measuring stations; the stream channel; in an average section; overflow of adjacent land; the usual channel boundaries; to reach flood stage; relative magnitudes of flood peaks; to be expressed in various terms; to include height above low water; height above flood stage; the direct or indirect result of precipitation; though the runoff; may be delayed or modified by the processes of freezing and thawing; flash flood; rapid increase of discharge in а river; to be marked by а precipitous rise in water level; to form а wall of water moving downstream; to be common in arid or in semiarid regions; to generate excessive runoff in an otherwise dry channel; may occur in humid regions; to concentrate the amount of runoff during an intense storm; to minimize the disastrous effects of floods; to predict their magnitude and frequency; by listing flood; to discharge according to magnitude; from this data; the time interval; can be expected; to be called the recurrence interval; each flood discharge.

Text (A)

Read the text «Flood»:

Flood is the overbank discharge of а stream. Most streams overflow their banks on an average of every 1,2 years. Although looked on as а disaster by man because he builds homes and industries on river floodplains, а flood is а natural event that often has beneficial results. The water carries sediment, which it deposits on the floodplain to renew and fertilize it; the water sinks into the soil to recharge the groundwater. А flood is а relatively high flow as measured by either gage height or discharge rate. Gage readings indicate levels of the water surface at measuring stations. Whenever the stream channel in an average section is overtaxed, causing overflow of adjacent land definitely outside the usual channel boundaries, the stream is said to have reached flood stage. Relative magnitudes of flood peaks may be expressed in various terms, including either height above low water, height above flood stage, or the corresponding rate of discharge.

Flood flows are normally the direct or indirect result of precipitation, even though the runoff may be delayed or modified by the processes of freezing and thawing, surface inequalities or indentations, interception on vegetal cover or through infiltration, -underground flow, and temporary storage in or release from reservoirs through either natural or artificial means of detention and regulation.

Flash flood is а sudden, rapid increase of discharge in а river. А flash flood is marked by а precipitous rise in water level that forms а wall of water moving downstream. Flash floods are common in arid or in semiarid regions, where an intense local гainstorm often generates excessive runoff in an otherwise dry channel. Flash floods may occur in humid regions if conditions in the watershed are such as to suddenly concentrate the amount of runoff during an intense storm.

One way to minimize the disastrous effects of floods is to predict their magnitude and frequency. А flood frequency analysis is made by listing flood discharges according to magnitude.

From this data the time interval at which such discharges can be expected is calculated. It is called the recurrence interval. Each flood discharge is then plotted against its recurrence interval, and the points form the frequency curve. These curves are used by engineers in building bridges and roads.

Exercises (B)

1. Establish compliance between parts of sentences:

1. flood is the overbank discharge 1. is to predict their magnitude

2. most streams overflow and frequency

their banks 2. even though the runoff may be

3. flood flows are normally the direct delayed or modified by the

or indirect result of precipitation the processes of freezing

4. a flood is а relatively high flow and thawing

5. flash flood is а sudden, rapid increase 3. on an average of every 1,2 years

6. one way to minimize the disastrous 4. of а stream

effects of floods 5. as measured by either gage

height or discharge rate

6. of discharge in а river

 

Text (B)

Read the text «Urban flooding» using a dictionary:

Urban flooding is the inundation of land or property in a built environment, particularly in more densely populated areas, caused by rainfall overwhelming the capacity of drainage systems, such as storm sewers. Although sometimes triggered by events such as flash flooding or snowmelt, urban flooding is a condition, characterized by its repetitive and systemic impacts on communities, that can happen regardless of whether or not affected communities are located within formally designated floodplains or near any body of water. There are several ways in which stormwater enters properties: backup through sewer pipes, toilets and sinks into buildings; seepage through building walls and floors; the accumulation of water on property and in public rights-of-way; and the overflow from water bodies such as rivers and lakes.

The flood flow in urbanized areas constitutes a hazard to both the population and infrastructure. Some recent catastrophes include the inundations of Nîmes (France) in 1998 and Vaison-la-Romaine (France) in 1992, the flooding of New Orleans(USA) in 2005, and the flooding in Rockhampton, Bundaberg, Brisbane during the 2010–2011 summer in Queensland(Australia). Flood flows in urban environments have been studied relatively recently despite many centuries of flood events. Some researchers have mentioned the storage effect in urban areas. Several studies have looked into the flow patterns and redistribution in streets during storm events and the implication on flood modelling. Some recent research has considered the criteria for safe evacuation of individuals in flooded areas.

However, some recent field measurements during the 2010–2011 Queensland floods showed that any criterion solely based upon the flow velocity, water depth or specific momentum cannot account for the hazards caused by velocity and water depth fluctuations. These considerations ignore further the risks associated with large debris entrained by the flow motion.

Exercises (B)

1. Сomplete the following sentences using suitable words and word-combinations given below:

considerations; hazard; flash flooding; flow velocity; storm sewers; communities; flood events; densely populated areas; accumulation; water depth.

1. Urban flooding is the inundation of land or property in a built environment, particularly in more.............................., caused by rainfall overwhelming the capacity of drainage systems, such as ....................... 2. Although sometimes triggered by events such as ......................... or snowmelt, urban flooding is a condition, characterized by its repetitive and systemic impacts on.........................., that can happen regardless of whether or not affected communities are located within formally designated floodplains or near any body of water. 3. There are several ways in which stormwater enters properties: backup through sewer pipes, toilets and sinks into buildings; seepage through building walls and floors; the ......................of water on property and in public rights-of-way; and the overflow from water bodies such as rivers and lakes. 4. The flood flow in urbanized areas constitutes a ......................to both the population and infrastructure. 5. Flood flows in urban environments have been studied relatively recently despite many centuries of....................... 6. However, some recent field measurements during the 2010–2011 Queensland floods showed that any criterion solely based upon the.........................., water depth or specific momentum cannot account for the hazards caused by velocity and .....................fluctuations. 7. These ............................ignore further the risks associated with large debris entrained by the flow motion.

 

 




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