River flow

ARKAN IBRAHIM 2015 | GAZIANTEP

RIVER FLOW BY:- ARKIAN IBRAHIM

A Report About

SUBMITTED TO: -

Y. Doc.Dr.Mazen KAVVAS

RIVER FLOW 11/09/2015

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


ARKAN IBRAHIM 2

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.


ARKAN IBRAHIM 3

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


ARKAN IBRAHIM 4

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


ARKAN IBRAHIM 5

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.


ARKAN IBRAHIM 6

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.


ARKAN IBRAHIM 7

-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


ARKAN IBRAHIM 8

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


ARKAN IBRAHIM 9

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.


ARKAN IBRAHIM 10

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.


ARKAN IBRAHIM 11

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.


ARKAN IBRAHIM 12

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


ARKAN IBRAHIM 13

(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


ARKAN IBRAHIM 14

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?


ARKAN IBRAHIM 15

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


ARKAN IBRAHIM 16

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.


ARKAN IBRAHIM 17

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.


ARKAN IBRAHIM 18

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.


ARKAN IBRAHIM 19

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

http://www.geologycafe.com/class/chapter11.html

River flow

Engineering

Transcript of River flow