CLASSIFYING NATURAL STREAMSACCORDING TO THEIR

MORPHOLOGICAL STATUS

CASE STUDYWADI WATIR IN SINAI- EGYPT

BY

Dr. Gamal Kotb

Overview

• Problem Definition

• Objectives

• Methodology

• Application

• Conclusions & Recommendations

Problem Definition

» Flash Flood Hazards

» Stream Reaches Stability

» Shortage of Stream Flow Data

Objectives

» Provide a measure tool to the decision maker, designers, and planners:-

-to choose the suitable streams of catchment for Hydraulic Structure construction;-to check the stability of the stream reaches;-to overcome the underlying causes of hydraulic structure damage;- to formulate feasible design of the hydraulic structure.

» Classify some studied streams in Sinai according to their erosion propensity.

Study Area

Field Investigations and Measurements

-Examining the proposed hydraulic structures sites;

-Sampling soil along the streams and analyzing the samples;

-Examining the geotechnical conditionsof the proposed sites;

-Examining the topographical conditionsBy executing a survey to the streams.

The Main CharacteristicsOf The Studied Streams

Stream Width( m)

Average Depth (m)

Slope D50,(mm)

Q50, (m3/sec)

Catchment's Area (km2 )

Zalaga 150 2 0.009 5 271 982

Swana 120 2 0.028 4.5 123 234

Shebaiha 90 1 0.030 3 33 70

Qudera 220 2 0.009 6.25 79 250

El Hegny 160 1 0.020 4 35 32

Sortoba 280 2 0.010 5.5 77 175

Sheira 250 2 0.020 3.8 105 215

El Shafallah 80 1 0.020 6.5 30 48

Abu El Thalam 190 1 0.020 6 59 69

El Meretba 90 1 0.005 4.5 41 56

Stream Power Approach

- Stream Power expresses the rate of Energy Expenditure in a stream reach under certainflow condition.

- According to Rhoads, (1987)

)(W/m S,u r gρ )(ωPower StreamMean 2=

- According to Nanson & Croke, (1992)

Mean Stream

Power, (W/m2)

Energy Expenditure

Classification

< 10 Low

10 - 300 Medium

>300 High

Application on Studied Streams

Mean Stream Power for Bankfull and 50-Year Discharge Conditions

0.00

500.00

1000.00

1500.00

2000.00

2500.00

3000.00

3500.00

4000.00

4500.00

5000.00

W1. Zalaga W2. Swana W3.Shebaiha

W6.Qadera

W5. ElHegny

W7.Sortoba

W8. Shaira E1. ElShafallah

E2. Abu ElThalam

E3. ElMeretba

Mea

n St

ream

Pow

er W

/m2

50 yr Dis.Cond. Bankfull Dis.Cond. Lower Limit Upper Limit

Application on Studied Streams

Mean Stream Power for Bankfull and 50-Year Discharge Conditions

Discharge m3/s Mean Stream Power W/m2

Bankfull Discharge 50-yr Discharge Bankfull Discharge 50-yr Discharge.

Zalaga 1505.94 217.00 886.40 127.73

Swana 2124.98 123.00 4864.09 281.55

Shebaiha 519.62 33.00 1699.14 107.91

Qadera 2208.71 79.00 886.40 31.70

El Hegny 754.25 35.00 924.90 42.92

Sortoba 2963.15 77.00 1038.16 26.98

Sheira 3741.54 105.00 2936.36 82.40

El Shafallah 377.12 30.00 924.90 73.58

Abu El Thalam 895.67 59.00 924.90 60.93

El Meretba 212.13 41.00 115.61 22.35

Stream

Proposed Dimensionless Approach

a) Dimensionless Mean Stream Power

SDgs

D 5.1505.1

1000

⎟⎠⎞

⎜⎝⎛

=ρ

ωω

b) Dimensionless Energy Limits

SDSDgs

5.150

5.1505.1

3.89

1000

10Limit Lower =

⎟⎠⎞

⎜⎝⎛

=ρ

SDSDgs

5.150

5.1505.1

116.73

1000

300Limit Upper =

⎟⎠⎞

⎜⎝⎛

=ρ

Dimensionless Stream Power Analysis of the Studied Streams

a) Stream Classification

0

0.5

1

1.5

2

0 1000 2000 3000 4000 5000 6000 7000 8000Dimentionless Mean Stream Power

Heig

ht (

m)

W1. Zalaga W2. Swana W3. Shebaiha W6. Qadera W5. El HegnyW7. Sortoba W8. Shaira E1. El Shafallah E2. Abu El Thalam E3. El Meretba

b) 50-Yr Flood Classification

Wadi Zalaga

00.5

11.5

22.5

0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00 3500.00 4000.00

Dimensionless Mean Stream Power Discharge (W/m2)

avg.

dept

h (m

)

D.M.stm Pr 50 yrs Dim. Mean St Pr Energy L.L W/m2 Energy U.L W/m2

Wadi Qadera

0

0.5

1

1.5

2

2.5

0.00 500.00 1000.00 1500.00 2000.00 2500.00 3000.00

Dimensionless Mean Stream Power Discharge (W /m2)

avg.

dept

h (m

)

D.M.stm Pr 50 yrs Dim. Mean St Pr Energy L.L W/m2 Energy U.L W/m2

Conclusions» A dimensionless mean stream power approach is proposed.

» Bank full discharge condition is not pertinent to be used while classifying the erosion propensity of streams

» Stability classification of the streams differed while applying the mean stream power and the proposed dimensionless approach.

» There is no extreme erosion problems are expected under 50-yr flood conditions by using both approaches.

» Wadi Shebiaha seems to have the highest instability tendency among the studied streams owing to its small median grain size and relatively high slope

» Wadi Qadera seems to have the lowest instability tendency among the studied streams owing to its large median grain size and relatively low slope.

Recommendations

» Careful studies of flood discharge must be made to beable to predict the changes in channel morphology especially when flood is flashy.» Check the applicability and problems predictive capability of the proposed dimensionless stream power.

» Study the suitability, efficiency and performanceof the existing hydraulic structures before and aftertheir construction by applying the dimensionless mean stream power approach.

» Use of the proposed approach in the planning and designing phases of watershed management and development projects.

» This approach should be applied to set a code for natural stream classification and define the suitable typeof hydraulic structures to be constructed.