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Geoenvironmental Disasters

Table 6 Weights, classes and scores for map layers

From: Flood vulnerable zones in the rural blocks of Thiruvallur district, South India

S.No

Map Layer

Classes

Rank

Weightage (%)

1.

Rainfall in mm

360–463

1

19.44

463–567

2

567–670

3

670–774

4

774–877

5

2.

Drainage Density

1–120

5

15.18

121–170

4

171–220

3

221–280

2

281–480

1

3.

Elevation in M

< 50

5

12.14

50–150

4

151–180

3

181–250

2

> 250

1

4.

Slope

0–2

5

11.71

2–3

4

3–5

3

5–10

2

More than 10

1

5.

Geology

Alluvium

4

05.40

Biotite Hornblende Gneiss

2

Epidote Hornblende Gneiss

3

Granite

2

Laterite

3

Quartz Gravel

2

Conglomerate Sandstone

1

Shale Sandstone

2

6.

Geomorphology

Duricrust

3

04.73

Moderately Weathered Pediplain

4

Pediment

4

Buried Pediment Shallow

5

Structural Hills

1

Residual Hill

1

Denudational Hills

1

Ridge/ Dyke

2

Inselberg

1

Channel Bar

3

Paleao Deltaic Plain

4

Shallow Alluvial Plain

4

Shallow Flood Plain /Flood Plain

5

Valley Fill

2

7.

Land use and landcover

Barren rocky area

2

13.11

Deciduous

1

Dry crop

2

Fallow Land

4

Forest plantations

2

Forest

1

Gullied / Ravenous land

4

Land with scrub

3

Land without scrub

3

Plantation

2

Reservoir /Lake /Tank

5

River

5

Settlements

3

Salt affected

2

Sandy area

1

Scrub forest

1

Wet crop

2

8.

Lineaments & Intersection

Lineament

4

06.59

Lineament intersection zone

5

9.

Zones of Tectonic Subsidence

Land subsidence

3

07.43

10.

Soil

Alfisols

2

04.27

Entosols

4

Inceptisols

3

Vertisols

1

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