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ARKAN IBRAHIM 2015 | GAZIANTEP
RIVER FLOW BY:- ARKIAN IBRAHIM
A Report About
SUBMITTED TO: -
Y. Doc.Dr.Mazen KAVVAS
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ARKAN IBRAHIM 1
Table of Contents Rivers (introduction) ................................................................................................................................ 2
Hydrological characteristics ..................................................................................................................... 3
Basin ....................................................................................................................................................... 5
Factors affecting runoff of the river ......................................................................................................... 6
Parts of a river system ............................................................................................................................. 8
Types of drainage networks and drainage patterns ............................................................................... 11
Sedimentations ..................................................................................................................................... 14
River stage ............................................................................................................................................ 16
References ............................................................................................................................................ 17
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Rivers Introduction: - a large natural stream of water flowing in a channel to the sea, a lake, or another river.
Rivers are the most important freshwater resource for man. Social, economic and political development.
Major river water uses can be summarized as follows: • sources of drinking water supply, • irrigation of agricultural lands, • industrial and municipal water supplies, • industrial and municipal waste disposal, • navigation, • fishing, boating and body-contact recreation, • aesthetic value.
Upstream use of water must only be undertaken in such a way that it does not affect water quantity, or water quality, for downstream users. Use of river water is, therefore, the subject of major political negotiations at all levels. Consequently, river water managers require high quality scientific information on the quantity and quality of the waters under their control. Provision of this information requires a network of river monitoring stations in order: • to establish short- and long-term fluctuations in water quantity in relation to basin characteristics and climate, • to determine the water quality criteria required to optimize and maintain water uses, and • to determine seasonal, short- and long-term trends in water quantity and quality in relation to demographic changes, water use changes and management interventions for the purpose of water quality protection.
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Figure 1: River Flow
Characteristics Upper Course Middle Course Lower Course
Slope
Width
Depth
Straightness
Load
Main work
Valley width
Type of load
usually steep
narrow
shallow
winding
little
large/small angular
erosion transportation
quite steep
quite wide
quite deep
meandering
some
medium/small rounded
Transportation
gentle
wide
deep
big meanders
lots
small+ rounded
transportation deposition
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Hydrological characteristics: -
1. River classification: -
The characteristics of the river, or rivers, within the total basin system are
related to a number of features. These features include the size, form and
geological characteristics of the basin and the climatic conditions which
determine the quantities of water to be drained by the river network.
Rivers can be classified according to the type of flow regime and magnitude
of discharge.
The flow regime may be subject to considerable modification by natural
impoundments, lakes, dams, or water storage. Flow characteristics may
also be changed by canalization, or requirements for water uses, such as
withdrawal for irrigation or other water supply needs, or by changes in
flood characteristics due to modifications of the soil infiltration as a result
of agriculture and urbanization.
The classification of rivers according to their discharge is generally more
satisfactory but has not, to date, been completely defined and accepted.
However, there are certain specified discharge rates which are widely used
to characterize river discharges and their annual variations. These include
the average peak discharges, the monthly or annual average discharge and
the average low discharge. A size classification based on discharge,
drainage area and river width is given in Table 1 The distinctions are
arbitrary and no indication of the annual variability in discharge is given.
River discharge, particularly in arid and sub-tropical regions, may range
from zero in the dry season to high discharge rates in large rivers during the
rainy season. Figure 2 A. The relationship between stream orders and hydrological
characteristics using a hypothetical example for a stream of order 8: (1)
Watershed area (A); (2) Length of river stretch (L); (3) Number of tributaries (n); (4)
Slope (m m-1); B. Stream order distribution within a watershed
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Table 1 Classification of rivers based on discharge characteristics and the drainage
area and river width
1 Depending on local conditions
2.Velocity and discharge: -
Hydrological characteristics are determined by velocity and discharge also.
The velocity (sometimes referred to as flow) The discharge of a river is the
single most important measurement that can be made because:
• it provides a direct measure of water quantity ,
• it allows for the calculation of loads of specific water quality variables,
• it characterizes the origins of many water quality variables by the
relationship between concentrations and discharge ,and
• it provides the basis for understanding river basin processes and is
essential for interpreting and understanding water quality.
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Basin: -
A drainage basin is a region drained by a principle stream extending from
upland headwater regions down to where the stream merges with another body
of water (a larger stream or river, lake, or ocean).
Fig. 3. Profile of a river drainage. The stream gradient for most rivers decreases
downstream.
Factors affecting runoff of the river: -
The discharge and its annual, as well as long-term, fluctuations are
primarily influenced by the characteristics of the drainage basin.
- Climatic, meteorological, topographical and hydrological factors play a
major role in the generation of river discharge.
-Small watersheds usually result in low median discharges with extremely
large ratios of peak and low discharge.
-Larger watersheds produce more uniform discharges. Large rivers with a
relatively uniform discharge regime during the year show a rather constant
ratio of average peak and low discharge
The principal factor causing large fluctuations in discharge is climate, which
determines the distribution of rainfall over the year.
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-The composition and structure of the sub-soil are also important factors.
Large differences can be observed between porous rocks, clays, marshy
soils and fissured rocks. Such geological conditions of the drainage basin
might cause variations in the discharge rates by a factor of two and in a few
cases even more.
-Vegetation also exerts an influence on the generation of river discharge
because it largely determines the quantity of surface run-off. Fluctuations
in discharge can be dampened by vegetation cover. In areas with little or no
vegetation, rainfall results in immediate surface run-off.
Figure 4 Theoretical hydrographs of a rain storm event of the same intensity in
two basins of equal size but with different infiltration rates: A. High infiltration rate
e.g. sandy soil, forest area; B. Low infiltration rate e.g. base crystalline rock,
urbanized basin. The increase in base flow is different in each case
-Discharge may also be controlled by factors other than storm conditions.
In all cold latitudes and mountainous regions, the effects of freezing and
thawing in glaciers are particularly important. Low discharge occurs during
glacial freezing in the winter and high discharge occurs during the summer
ice melt between May and October. The variations between winter low
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discharge and summer high discharge are less pronounced downstream.
This is due to the increasing influence of storm related run-off and snow
melt.
Parts of a river(basin) system: -
Every river is part of a larger system—a watershed, which is the land drained by a
river and its tributaries. This diagram shows some common characteristics of a
river system. Every river is different, however, so not all rivers may look exactly
like this illustration.
The river source, also called the headwaters, is the beginning of a river. Often
located in mountains, the source may be fed by an underground spring, or by
runoff from rain, snowmelt, or
glacial melt.
A tributary is a smaller stream
or river that joins a larger or
main river.
The main river is the primary
channel and course of a river.
A fully-developed floodplain is
relatively flat land stretching
from either side of a river,
which may flood during heavy
rain or snowmelt. Built of
materials deposited by a river,
floodplain soil is often rich in
nutrients and ideal for growing food. Fig.5.Parts of a river system
A meander is a loop in a river channel. A meandering river winds back and forth,
rather than following a straight course.
Upstream is in the direction of or nearer to the source of a river
Wetlands are low-lying areas saturated with water for long enough periods to
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support vegetation adapted to wet conditions. Wetlands help maintain river
quality by filtering out pollutants and sediments, and regulating nutrient flow.
The river mouth is the place where a river flows into a larger body of water, such
as another river, a lake, or an ocean.
A watershed boundary, also called a drainage divide, marks the outer-most limit
of a watershed. A watershed is a tract of land drained by a river and its
tributaries. Anything that affects a watershed may eventually impact its
tributaries and river as well as the water body at the mouth of the river. People's
actions within a watershed can affect the overall quality of its rivers.
Downstream is in the direction for nearer to the mouth of a river.
Fig. 6. Waterfalls and rapids are common features in headwater regions. Upland stream and river valleys typical have a V-shape.
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Fig. 7. River features
A splay is a small fan-shaped or outspread alluvial deposit formed where an overloaded stream breaks through a levee (artificial or natural) and deposits its material (often coarse-grained) on the floodplain (Figure 8). Like meandering, the formation of splays contributes sediments to flood plains, particularly during times of flood. A delta is an accumulation of sediments at the mouth of a river that may consist of a network of distributary channels, wetlands, bars, tidal flats, natural levees and beaches that typically shift from on location to another. Delta shape is dependent of dominant current conditions where the mouth of the river: tide-, sea wave-, and storm-dominated.
A distributary is the opposite of a tributary. A distributary channel is a stream that branches off and flows away from a main stream channel. Distributaries are a common feature of river deltas where slowing water and interaction of ocean tides, waves, and currents influence the distribution of sediments along a coastline. Distributaries can form along floodplains near the mouths of streams entering larger rivers or lakes.
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Fig. 8. Splays and distributary channels on a river delta.
Types of drainage networks and drainage patterns: -
A drainage pattern is a pattern created by stream erosion over time that reveals characteristics of the kind of rocks and geologic structures in a landscape region drained by streams (Figure 9). Dendritic drainage patterns are randomly shaped systems that commonly form on heterogeneous bedrock, such as flat-lying sediments or sedimentary rocks where there is nothing to influence the flow of water.
Parallel drainage patterns develop on inclined surfaces such as gently dipping strata. Trellis drainage pattern are common in terrain with folded bedding (parallel series of anticlines and synclines). Rectangular drainage patterns are common in fractured and faulted hard bedrock (usually igneous and metamorphic rocks). Deranged drainage patterns occur in areas that geologic events have disrupted the landscape. Example of deranged drainages occur in recently glaciated landscapes and in active volcanic regions.
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Radial drainage patterns are associated with circular-shaped basins and domes
Fig. 9. Stream drainage patterns can reflect the structure and composition of
bedrock.
Meandering - the process creating winding river channels
A meander is a bend in a sinuous watercourse. Meandering is the process
when the faster-moving water in a river erodes the outer banks and widens
its valley, and the slower-moving water on the inner side of the bend
becomes a place where sediments are deposited (point bars). As a result,
rivers tend to constantly change their course over a floodplain over time
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(Figures 10 and 11).
An oxbow is a crescent lake on a stream floodplain formed when a
meandering stream channel is cut off and isolated by changes in a stream
channel.
Fig. 10. Stream channel flow results in meandering forming cut banks and point
bars (see Fig. 11below).
Fig. 11. Example of a meandering river channel with cutoff channels and oxbows.
in order to protect surface water resources and optimise their use, soil loss
must be controlled and minimised. This requires changes in land use and
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land management, which may also have an impact on water quality.
Control of the siltation rate in reservoirs requires that adequate data are
available at the design stage. This, in turn, demands an understanding of
sediment transport and appropriate methods for measuring sediment load
and movement.
Sedimentations: -
Sediment is the loose sand, clay, silt and other soil particles that settle at the
bottom of the river. Sediment transport is critical to understanding how rivers
work because it is the set of the processes that meditates between the flowing
water and the channel boundary. The flow of water in the river lead to the
transportation of the particles concurrently along the flow. Sediment loads are
transported at the streambed by sliding, rolling and bouncing. The particles that
are transported by the water in the river will be deposited and form the sediment
pattern on the river bed. The sediment pattern will differ based on the different
features of the river. The size distribution of the sediment also will be different.
Sediment Supply versus Stream Gradient
A river or stream is rarely in a state of equilibrium when it comes to erosion and
deposition processes. In general, upland regions receive the greatest amount of
precipitation, and are places where sediments are being generated. If tectonic
forces are causing the land to rise, stream gradients increase, and streams carve
deeper into their valleys, forming canyons (Figure 12).
Where streams lose their gradient, they slow down and sediments are deposited,
filling in their valleys. Braided streams are common in landscapes where stream
valleys are overloaded with sediment. Streams dropping their sediments are
filling their channels, causing the channels to constantly migrate across a
floodplain (Figure 13). Changes in climate can cause changes in the amount of
sediments contributed to a stream flood plain.
How rivers erode?
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HYDRAULIC ACTION The force of the water weakens and breaks up the
rocks
ABRASION The material carried in the river wears away the river bed
ATTRITION As the pebbles carried by the river crash into each other,they
become smaller and rounder
SOLUTION The water in the river dissolves the minerals in the rocks
How rivers transport?
Traction: Rolling stones along the river bed .( needs lots of energy)
Suspension: Clay sized particles are carried along by the river flow
Saltation: Sand sized particles bounce along the riverbed
Solution: Some minerals are dissolved by the river water.
river flow
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Fig. 12. Colorado River in the Grand Canyon, Arizona. Canyons form where stream
erosion dominates over deposition.
Fig. 13. Formation of stream terraces along a rejuvenated stream valley. Climate
changes, sea level changes, and tectonic uplift can cause streams to cut into their
floodplains producing abandoned stream terraces.
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River Stage: -
River systems represent the dynamic flow of drainage water, which is the final
product of surface run-off, infiltration to groundwater and groundwater
discharge. The general relationships between these and the nomenclature for a
river transect are summarized in Figure 14.
Figure 14 Generalized cross-section of a river showing the relationship between
physical features and the low and high water stages
Studying river stage is very important manner as it provides a continues
information about the amount of water flowing in a river with previous measured
river stages one will be able to predict the undesired upcoming event relevant
with a specific stage of water in the river which is very important for safety
especially from flood disasters. As river stage gives as information about the
region response according to different stages of water in the river.
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Conclusion: -
From the above information it can be understand that rivers are playing a major
role in the many aspects of our life which is also in a continues change in its
physical properties wither naturally or by human affects .it can also be figured
that to protect the quantity and quality of water in the river as it is a major source
for fresh water uses a good quality plan is important for managing water
resources.
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References: -
1- process of settling of suspended material by RAHAYU BINTI RAZALI
2- http://www.geologycafe.com/class/chapter11.html
3- Water Quality Monitoring - A Practical Guide to the Design and Implementation of Freshwater
Quality Studies and Monitoring Programs by Jamie Bartram and Richard Balance
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