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IAPRS & SIS, Vol.34, Part 7, "Resource and Environmental Monitoring", Hyderabad, India, 2002
EROSION HAZARD ASSESSMENT AND CONSERVATION PLANNING IN PART OF
NORTH-EAST HIMALAYA (INDIA) USING REMOTE SENSING AND GIS
Suresh Kumar? , Sazo, C?., Renthlei, V*., Jamir, R?. and Pande, L.M*
“Indian Institute of Remote Sensing, 4- Kalidas Road, Post Box. No. 135, Dehradun — 248001 (India)
E-mail: Suresh_kumar@iirs.gov.in, Phone: +91-135-745526
" Department of Horticulture, Government of Nagaland (India)
* Department of Horticulture , Government of Meghalaya (India)
^Soil & Water Conservation Department, Government of Nagaland (India)
KEY WORDS: Soil erosion hazard, USLE, Watershed prioritization, Silt yield index, N-E Himalaya
ABSTRACT:
The Universal Soil Loss Equation (USLE) and Silt Yield Index (SYI) models were employed to predict soil erosion hazards and
sediment yield to prioritize sub-watershed for conservation planning of the Umkhen watershed in the Meghalaya state in North-East
Himalayan region in India. The watershed was divided into 29 sub-watersheds. Extensive field survey was carried out to collect soil
samples in each physiographic / land use units and ground truth for land use / land cover. The land use / land cover map was
prepared from visual analysis of IRS LISS III & PAN merged satellite imagery at scale of 1:25,000, whereas digital elevation model
(DEM) was generated from topographic map to derive terrain attributes. The various thematic layer pertaining to the models were
generated in raster based GIS software and integrated to assess soil loss and sediment yield. Erosion hazard analysis reveals that
33.83 percent of the watershed predicted to have very severe erosion hazard whereas 22.95, 19.91 and 13.95 percent area have
severe, moderate and slight erosion hazards, respectively. Land capability was interpreted from soil, land use and terrain type to
suggest suitable conservation measures.
1. INTRODUCTION
Soils are vital natural resource that not only insures the food
and fiber needs of the people, but also insures the economic
prosperity in agrarian economy. Slash and burn agriculture
(shifting) is dominant food production system in north-east
Himalaya of India. The system is ecologically stable under
cycle of 25-30 years, but it has reduces to 1-3 years due to
increase in population pressure. In some of the area, Jhum
cycle has crossed the critical limits resulting complete
denudation of forest known as bun agriculture. Due to the
reduction of fallow cycle and deforestation for shifting
cultivation, the resilience of ecosystem has broken down and
resulted significant loss in soil productivity and rampant
increase in soil erosion under various landuse system.
Soil erosion due to water is main cause of land degradation in
the region. N-E Himalayan region comprises mainly of
mountain ranges with narrow valleys. The soils are increasingly
eroded due to improper utilization of natural resources,
unscrupulous deforestation and shifting cultivation. Moreover,
the hilly nature of the terrain having average annual rainfall of
2232 mm is very conducive to soil erosion. Soil erosion hazard
most commonly quantified using annual soil loss rates
(Herweg, 1996). The Universal Soil Loss Equation (USLE),
though an emperical multiplicative approach is still widely used
model for prediction of soil erosion. Soil loss due to water
erosion is a complex process of erosivity of rainfall and
erodibility of soil as described by USLE (Wischmeir and Smith,
1978). Singh (1978) studied soil erosion in shifting areas
reported, soil loss varying from 2.1 to 201 t halve.
Cultivation of tuber crops on raised beds laid out along slope
have been found to result soil loss to the tune of 40-50 t ha™
yr! ( Singh and Singh, 1981). The feasibility of prioritization
of watershed on the basis of sediment yield index have been
proposed by All India Soil and Land Use Survey (AIS & LUS,
1991) for conservation planning (Sidhu et al. 1998).
USLE and SYI models were used in the present study to assess
erosion hazards and to prioritize the Umkhen watershed for
conservation planning as it was possible to generate thematic
(factor) layers and their integration using remote sensing and
GIS techniques.
2. DESCRIPTION OF THE STUDY AREA
The watershed lies in the East Khasi Hills district of Meghalaya
covers 167.57 sq. km. between latitudes of 25? 30' 0" to 25? 38'
0" N and longitudes of 91°50” 0” to 92° 10' 0" E. Altitude
ranges from 860m to 1860m. The area represents the typical
sub-tropical northeastern region. The mean summer and mean
winter temperature is 23°C and 3°C, respectively. The average
annual rainfall of the area is 2087 mm with more than 80%
occur during the period from April to October.
Geologically, the area comprises of (i) Shillong group of rocks
— quartzite, phyllite, conglomerate; (ii) arehan gneiss complex,
and (iii) granite rocks and tertiary sediments consisting mainly
of sandstone, limestone, siltstone, shale and pebbles, clays,
conglomerates. The soil belongs to mostly Ultisols, followed by
Inceptisols, Entisols and Alfisol orders. Continuous high
intensity denudation by bun and shiftiing cultivation causes
different erosional phases of soils. The soil materials removed
continuously by erosion and deposited on the lower slopes.
Thus, reducing soil depth on the slopes.
The watershed has rural population of 33,501 covering 31
villages. Agriculture is the mainstay of the people. Around
26.64% of the watershed is under agriculture. The main crops
grown are paddy (uplan and lowland), maize and vegetables.
Cultivation is done on valley fields as well as on the sloping hill
lands. Bun is modified system of shifting cultivation. Under
the bun system , raised bed of variable size prepared along the
hilly slope are used for cultivation of vegetable crops viz.
