What are the factors that make the findings of the stream under study

different from the characteristic feature of an ideal stream

Discussion Topic:

Differences between stream under study and ideal stream (upper course)

Differences between stream under study and ideal stream

(upper course)

Stream under study Ideal stream

1.Discharge Relatively larger Very Small

2.Width Wider v-shaped river bed

Sharp V-shaped river bed

3.Depth Deeper than middle course

Shallow

4.Width-deep ratio

Larger smaller

Next

Differences between stream under study and ideal stream

(upper course)

Stream under study Ideal stream

5.Pebble roundness

Partly polished river load

Angular river load

6.Gradient Gentle Very steep

7.Velocity Relatively higher Low

Next

Differences between stream under study and ideal stream

(upper course)

Stream under study Ideal stream

8.Water flow

Less turbulent Turbulent with eddies

9.Special feature

No pot hole is found. Uneven river bed, due to abrasion, and forms pot holes.

Next

Sharp V-shape

Differences between stream

under study and ideal stream (middle course)

Differences between stream under study and ideal stream

(middle course)

Stream under study Ideal stream

1.Discharge Smaller than upper course

Medium

2.Width Relatively wider than upper course

Board V-shaped

3.Depth Less deep than upper course

Medium deep

Next

Differences between stream under study and ideal stream

(middle course)

Stream under study Ideal stream

4.Pebble roundness

Angular river load can be found

Polished river load

5.Gradient Very gentle Gentle but steeper than lower course

6.Velocity Lower than upper course

Medium

Next

Differences between stream under study and ideal stream

(middle course)

Stream under study Ideal stream

7.Water flow

More calm Less turbulent

8.Special feature

Erosion and deposition take place

Next

Erosion at outer bankDeposition at inner bank

Erosion at outer bank

Deposition at inner bank

Differences between stream under study and ideal stream (Lower course)

Differences between stream under study and ideal stream

(Lower course)Stream under study Ideal stream

1.Discharge Smaller than middle course (site 6)

Large

2.Width Narrower than site 5 Wide

3.Depth Less deep than middle course

Deep

4.Width-deep ratio

Site 6’s ratio is less than site 5’s.

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Differences between stream under study and ideal stream

(Lower course)Stream under study Ideal stream

5.Pebble roundness

River load deposited due to construction of dykes.

Polished and round river load

6.Hydraulic radius

Site 6’s radius is less than site 5’s.

Lower the course, higher the radius is.

7.Velocity Lower than upper course

Medium

Next

Differences between stream under study and ideal stream

(Lower course)Stream under study Ideal stream

8.Special feature

Dykes are built.

Next

Dykes narrowing the lower course.

Why the chosen stream is different from the ideal stream ??

Human Factor !!

Human Factor

The chosen stream sections in Pak Tam Chung

modified by human

-Bumping station

-Construction work

-Weit

-Holiday Village

-Catchwater

Human FactorDISCHARGE

-Upper course smaller discharge

Catchwater(引水道 ) built up, more discharge because of the water collection

Weir(水堰 ) block the water flow, it smaller the discharge

-Middle course greater discharge

The Holiday Village ‘s drainage system collect to the river, increase the discharge

Weir block the water flow, it smaller the discharge

-Lower course discharge decrease

The bumping station bump the water away