SLUSI
Land Degradation Mapping (LDM) Survey
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Methodology

The methodology for land degradation mapping using remote sensing techniques developed by the organization is based on the expertise in the field of soil survey and remote sensing acquired since inception. Multi-date False Colour Composite (FCC) generated out of IRS LISS II sensor has been used for interpretation purposes. Standard procedure of image interpretation techniques covering the steps i.e., recognition, identification, analysis and inferences have been followed for mapping purposes.

Legend Development

Legend development is a state of art in land resource mapping to depict the various land information on map in a comprehensive manner.  According to the conceptualization of mapping, various kinds of degraded lands have been symbolized alphanumerically. For example water erosion has been symbolized as “We” whereas degradation due to water logging has been denoted as “Wl”.   The kind of degraded lands have further been segregated based on degree of severity and have been denoted by suffixing a numerical 1 to7.  A land suffering from water erosion “We” could therefore be further segregated based on degree of severity.  For example water erosion with severe and very severe sheet, rill and few gullies could be denoted as “We1” and “We2” respectively. Similarly, deep ravines having depth greater than 3 m could be symbolized as “We6”.To identify and delineate the occurrence of various kinds of the degraded lands under major landscape is essential for proper planning of any developmental activities.  Keeping this in view, the whole country has been divided into four major landscape classes as per universal terminology (Anon, 1993). The landscape classes viz.; plain land, undulating land, rolling land and hilly/mountainous land based on slope ranges has been considered in the construction of mapping unit.  Small English alphabet denoting the landscape class has been used as suffix in the mapping unit.  For example, plain land with very severe water induced soil erosion is depicted on map as “We2a”.   In order to make the legend more users friendly and to understand the degradation process under different land uses, the mapping unit has been further expanded with a numeral as suffix indicating the major land use classes.  Major land use namely, agriculture, forest, plantation and other land uses have been used as suffix in formulating the mapping unit. The agriculture land situated in a gently slopping plain suffering from severe sheet erosion can be symbolized as ‘We1a1’ on map. The details of the legend are given in the appendix.  The legend thus developed by AISLUS has been subsequently modified based on the experience gathered during mapping.  The legend was discussed at national level with the various organizations dealing with land resource mapping and subsequently modified based on the experience gathered in the process of mapping.

Legend for Land Degradation Mapping

        Kind of Land Degradation

S. No.

Kind of Land Degradation

Symbol

1.

Water Erosion

We

2.

Wind Activity

Wa

3.

Waterlogging

W1

4.

Salt Affliction

Sa

5.

Shifting Cultivation (Jhum Cultivation)

Sc

6.

Mine dumps

Mn

7.

Rock quarry

Rq

8.

Area affected by Industrial Effluents

Ie

9.

City Waste/Garbage dumps

Cw

10.

Landslide/ Land slip

Ls

11.

Brick Kiln affected area

Bk

12.

Mud Flat

Mf

13.

Salt Flat/Salt Pan

Sf/Sp

14.

Rockout Crop / Rocky Waste/ Stony Waste

Rw

15.

Glacial  Moraine

Gm


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  Degree of Severity of Degradation
       

S. No.

Kind Degradation

 Severity

Symbol

1.

Water Erosion (We)

Severe (Sheet, rill and few gullies)

1

 

 

Very severe (gullied land open scrub thin vegetation)

2

Very Severe (gullied land medium to thick vegetation)

3

Shallow ravines (Depth < 3m) Open scrub/Thin vegetation

4

Shallow ravines (Depth < 3 m) Medium to thick vegetation

5

Deep ravines  (Depth  > 3 m)  Open scrub and thin vegetation

6

Deep ravines (Depth > 3 m) Thick to medium vegetation

7

2.

Wind Activity (Wa)

Severe (active plain and dune)

1

 

 

Very severe (active and shifting dunes and sand casting)

2

 

 

Coastal sand casting

3

3.

Waterlogging (W1)

Seasonal (affecting one crop; 4-6 months submergence)

1

 

 

Permanent (affecting two crops; more than 6 months submergence)

2

 

 

Inland Marshes

3

4.

Salt Affliction (Sa)

Moderately Saline

1

 

 

Strongly Saline

2

Moderately Saline Alkali

3

Strongly Saline Alkali

4

Moderately  Alkali

5

Strongly Alkali

6

5.

Shifting Cultivation (Sc)

Current Jhum land

1

 

 

Abandoned Jhum land

2

6.

Mine dumps (Mn)

 

1

7.

Rock Quarry (Rq)

 

1

8.

Area affected by Industrial Effluents (Ie)

 

1

9.

City Waste/ Garbage dumps (Cw)

 

1

10.

Land  Slide/Slips (Ls)

 

1

11.

Area affected by Brick Kiln (Bk)

 

1

12.

Mud Flat (Mf)

 

1

13.

Salt Pan/Salt Flat (Sp/ Sf)

 

1

14.

Rockout Crop/ Rocky Waste/ Stony Waste (Rw)

 

1

15.

Glacial Moraine (Gm)

 

1

 Major Landscape Classes and Percent Slope Range

S. No.

Class

Landscape Description

Range in percent slope

Symbol

1.

Plain lands

Level toGently sloping

0-5

a

2.

Undulating lands

Gently to Moderately slopping Undulating

3-10

b

3.

Rolling land

Rolling

10-15

c

4.

Hilly/Mountain

Hills, Mountains

> 15

d

 

 

 

 

 

 

 

 

 

 

             Major Land Use Classes

S. No.

Land Use Class

Remarks

Symbol

1.

Agriculture

All types of agriculture excepting orchards/fruit crops, plantation, etc.

1

2.

Forest

All types of forest i.e. P.F., R.F. and other forests shown on toposheets

2

3.

Plantation

All types of plantation crops, fruit crops, tea, coffee, rubber and orchards etc.

3

4.

Others (including open scrub, pasture lands, etc.)

All other lands under scrub.

4

 

 

 

 

 

 

 

      Chemical Characteristics of Salt-affected Soils

Type of Salt affected soil

pH

EC (dS/ m)

ESP

Predominant anions / cations

Saline Soils

< 8.5

> 4.0

< 15

Chlorides, sulphates some times nitrites of sodium/small amount of bicarbonates

Saline-alkali

> 8.5

> 4.0

> 15

Carbonates and bicarbonates of sodium

Alkali Soils

> 8.5

< 4.0

> 15

Carbonates and bicarbonates of sodium

 

 

 

 

 

 

Source: United State Salinity Laboratory Staff (1969); Diagnosis and Improvement of Saline and Alkali Soils. Agriculture Handbook No. 60

Key to Degree of Salinity and / or Alkalinity

Degree of Salinity and / or Alkalinity

Salinity EC(dS/m)

Alkalinity

pH

ESP

Slight

4  -  8

8.5  -  9.0

< 15

Moderate

8  -  30

9.0  -  9.8

15  - 40

Strong

> 30

> 9.8

> 40

 

 

 

 

 

 

 

 

 

 

 

Note: Change in land use as per image over that of shown on toposheet is to be indicated in parenthesis.

Example: Plantation as per image and agriculture as per toposheet to be symbolized by 1/3 as major land use.

Orchards, social forestry plantation tea, coffee etc. are included under “Plantation” land use and to be symbolized as “3”

Status of Mapping: SLUSI has so far covered 65 districts spread over in different agro-climatic regions of the country. Spatial distribution of various kinds of degraded lands with extent in a district is available in the report which is helpful for macro-level planning. It is an in-house programme of the organization which has been taken in a limited scale due to over burden with other ongoing activities. The mapping needs to be pacified with a mission approach. Department of Agriculture and Cooperation and Department of Space took the initiative of launching of National Mission for Soil and Land Degradation Mapping (Venkataratnam and Das, 2002) which will help to accomplish the task of land degradation mapping within stipulated time.

Reclamation of Degraded Lands: The land degradation mapping on 1:50,000 scale using remotely sensed data provides the first hand information about the extent and spatial distribution of degraded lands in a district that allows macro level planning for development of the degraded lands. But reclamation of any kind of degraded land is a location specific issue that requires to be dealt at micro level.

Land reclamation aims at improving the soil productivity and restoring fragile eco-system which is essentially the interplay between soil conservation and degradation processes as illustrated below.

Detailed database on soils and other associated information is thus essential for soil and land reclamation purposes.

District Information System for Degraded Lands:

            The Database with spatial distribution of various soil and land attributes is a pre-requisite for development of strategic planning of any land development programme.  The district-wise data base on degraded lands will not only help for rehabilitation planning of degraded lands but will be the vital base for monitoring purposes.  The existing database of any land attributes could be updated using remote sensing technique that will facilitate in identifying the changes being taken place due to dynamic processes that are operating on land.

The voluminous database thus generated often creates problem in handling for compilation and analytical purposes manually resulting delay to support the decision making process.  The technological advancement in the field of management of spatial data in the form of Geographic Information System revolutionized not only the management of voluminous data in a systematic manner but it allows manipulation, analysis and retrieval of map and statistical information in desired format accurately and quickly. 

The information system on degraded land in the country should be developed using remote sensing and Geographic Information System towards strategic development of degraded lands and monitoring the status in a periodic time scale.  Such kind of information system will be a valuable tool for management of degraded lands and national auditing as well.

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