Flash Floods Causative Criteria

Wadi Surr

Wadi Zawhi

Class

Susceptibility Class Ranges and Ratings

Susceptibility Class Score

Class

Susceptibility Class Ranges and Ratings

Susceptibility Class Score

Weight (%)

Topographic Wetness Index (TWI)

−7.49 - −4.91

Very Low

1

−7.37 - −4.76

Very Low

1

4

−4.9 - −2.95

Low

2

−4.75 - −2.95

Low

2

−2.94 - −0.37

Moderate

3

−2.94 - −0.56

Moderate

3

−0.36 - 3.25

High

4

−0.55 - 2.84

High

4

3.26 - 18.84

Very High

5

2.85 - 11.08

Very High

5

Elevation (Meters)

0 - 291

Very High

5

−2 - 269

Very High

5

9

292 - 542

High

4

270 - 565

High

4

543 - 851

Moderate

3

566 - 961

Moderate

3

852 - 1280

Low

2

962 - 1402

Low

2

1281 - 2291

Very Low

1

1403 - 2211

Very Low

1

Slope (Degree)

0 - 6.25

Very High

5

0 - 4.9

Very High

5

15

6.26 - 13.85

High

4

4.91 - 12.47

High

4

13.86 - 21.67

Moderate

3

12.48 - 22.93

Moderate

3

21.68 - 30.15

Low

2

22.94 - 34.51

Low

2

30.16 - 56.96

Very Low

1

34.52 - 56.78

Very Low

1

Stream Power Index (SPI)

0 - 0.5

Very Low

1

0 - 0.1

Very Low

1

13

0.51 - 2.06

Low

2

0.11 - 0.36

Low

2

2.07 - 4.45

Moderate

3

0.37 - 0.76

Moderate

3

4.46 - 8.89

High

4

0.77 - 1.34

High

4

8.9 - 14.17

Very High

5

1.35 - 2.47

Very High

5

Terrain Roughness Index (TRI)

0.11 - 0.34

Very Low

1

0.11 - 0.31

Very Low

1

3

0.35 - 0.42

Low

2

0.32 - 0.41

Low

2

0.43 - 0.49

Moderate

3

0.42 - 0.48

Moderate

3

0.5 - 0.57

High

4

0.49 - 0.56

High

4

0.58 - 0.83

Very High

5

0.57 - 0.8

Very High

5

Normalized Difference Vegetation Index (NDVI)

−0.06 - 0.01

Very High

5

−0.07 - −0.01

Very High

5

7

0.02 - 0.03

High

4

0 - 0.02

High

4

0.04 - 0.06

Moderate

3

0.03 - 0.04

Moderate

3

0.07 - 0.1

Low

2

0.05 - 0.06

Low

2

0.11 - 0.31

Very Low

1

0.07 - 0.14

Very Low

1

Sediment Transport Index (STI)

0 - 97

Very Low

1

0 - 73

Very Low

1

3

98 - 420

Low

2

74 - 277

Low

2

421 - 992

Moderate

3

278 - 673

Moderate

3

993 - 1789

High

4

674 - 1201

High

4

1790 - 2749

Very High

5

1202 - 1683

Very High

5

Stream Order

1st

Very Low

1

1st

Very Low

1

23

2nd

Low

2

2nd

Low

2

3rd

Moderate

3

3rd

Moderate

3

4th

High

4

4th

High

4

5th

Very High

5

5th

Very High

5

Flow Accumulation (Pixels)

0 - 2776

Very Low

1

0 - 1370

Very Low

1

13

2777 - 9590

Low

2

1371 - 5022

Low

2

9591 - 27,257

Moderate

3

5023 - 12,897

Moderate

3

27,258 - 52,999

High

4

12,898 - 18,831

High

4

53,000 - 64,356

Very High

5

18,832 - 29,103

Very High

5

Geological Formation

Quaternary Sand, Gravel, and Silt Deposits

Not Suitable

1

Quaternary Sand, Gravel, and Silt Deposits

Not Suitable

1

10

Atiyah Monzogranite, Alkali-Feldspar Granite

Less Suitable

2

Marabat Suite, Atiyah Monzogranite

Less Suitable

2

Conglomerate, Siltstone and Silicic Volcaniclastic Rocks

Moderate

3

Alkali-Feldspar Granite

Moderate

3

Andesitic lavas, Porphyritic Amphibolite and Pyroclastic Rocks

Suitable

4

Pyroclastic Rocks

Suitable

4

Igneous Intrusive Rocks

High Suitable

5

Total

100