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. |