Interpretation of land use/land cover dynamics with the application of geospatial techniques in sarbari khad watershed of Himachal Pradesh, India

Land Use/Land Cover (LULC) changes represent anthropogenic transformation of natural landscape. These changes are an important tool in developing strategies for the management of natural resources as well as monitoring environmental changes. LULC mapping and monitoring is required to understand the causes and consequences of over exploitation of natural resources such as land, soil, forest and water. By assessing the uses and misuses of resources and identifying the reasons for misuses, the measures for sustainable development of resources in the fragile Himalayan watersheds can be identified and implemented. The main objective of the present study is to assess the land use/land cover changes in the Sarbari Khad watershed of Kullu Valley. The Sarbari Khad watershed is part of Beas River basin. The changes in LULC have been detected by using remote sensing and GIS (Geographical Information System) techniques for a period of twenty-one years (2000–2021). The satellite images of the National European Space Agency Sentinal-2 of November, 2021 and LandSat-7 image of November 2000 were processed with the help of ERDAS Imagine (2015) and Arc View (3.2a) software. This study reveals that substantial amount of deforestation and snow cover retreat has occurred during this period of two decades due to anthropogenic activities such as expansion of agriculture, especially horticulture, tourism and infrastructure development.


Introduction
The LULC (Land Use and Land Cover) changes are vital component in planned strategies for sustainable development. They are key to natural resource management and monitoring. Land cover represents the biophysical condition of a watershed like natural vegetation, snow cover etc. On the other hand, land use represents anthropogenic modifications of land to fulfill the socio-economic needs and wants of people like settlements, agricultural land uses, transport infrastructure and other build-up areas. Thus, LULC are two basic concepts for understanding the natural landscape and its use by humankind (Manonmani et al., 2010). The LULC changes have emerged as Abstract Land Use/Land Cover (LULC) changes represent anthropogenic transformation of natural landscape. These changes are an important tool in developing strategies for the management of natural resources as well as monitoring environmental changes. LULC mapping and monitoring is required to understand the causes and consequences of over exploitation of natural resources such as land, soil, forest and water. By assessing the uses and misuses of resources and identifying the reasons for misuses, the measures for sustainable development of resources in the fragile Himalayan watersheds can be identified and implemented. The main objective of the present study is to assess the land use/land cover changes in the Sarbari Khad watershed of Kullu Valley. The Sarbari Khad watershed is part of Beas River basin. The changes in LULC have been detected by using remote sensing and GIS (Geographical Information major challenges as they are mostly unplanned and their consequences are reflected in the form of ecological problems like deforestation, soil erosion, landslides, reduction in biodiversity, changes in hydrological processes, land degradation and enhanced food insecurities. The complex interactions of natural land capabilities and cultural backgrounds together determine the land use and land cover situation of a particular watershed. The LULC changes in Himalayan region are consequences of accelerating population and economic growth. Although in short-term economically these changes may be beneficial but long-term stability and sustainability of ecosystems is of prime concern, especially in fragile watersheds of Himalayan region (Government of India (GOI), 2010; Jodha, 2000;Price, 1997;Sati, 2006;ICIMOD, 2010). Therefore, to prevent and minimize the adverse impacts of LULC changes and for sustainability of the watersheds as ecosystems, LULC changes analysis is essential. These days geospatial technologies (Remote Sensing and GIS) play an important role in data acquisition as well as processing for the detection of LULC changes. These techniques efficiently help in LULC analysis in spatio-temporal context.
The researchers in their studies on LULC change analysis have focused mainly on establishing links among aspects such as population pressure, economic diversification, technological advancement and biophysical characteristics of watersheds. Population explosion and goal of maximization of profit are the key drivers of these changes. Lack of land use policies and poor implementation of policies have resulted into faulty land use practices. Thus, understanding and identification of the drivers of LULC changes is a matter of great significance. This type of research not only helps in understanding the consequences of LULC changes and but also in formulating land management policies for the sustainability of the watersheds as ecosystems as well as socio-economic units. Land use/cover is largely determined by physical conditions such as altitude, slope, geological structure and cultural aspects such as level of technology, socio-economic and institutional set-up (Rai et al., 1994;Singh & Panchal, 2015). The LULC changes work as an important tool in monitoring changes in the cultural and natural landscapes and in developing strategies for sustainable management of resources (Singh & Dev, 2011;Turner, 2001;Turner & Meyer, 1994). The present study is focused on the analysis of LULC changes between 2000 and 2021 in the Sarbari Khad watershed of Kullu District, Himachal Pradesh, India with the help of geospatial technologies. The multi temporal and multi spectral images of the LANDSAT 7 (November 2000) and Sentinal 2 (November 2021) have been processed with the help of GIS software and required ground verifications. The objectives of the present study are following-(i) to identify or detect LULC changes in the Sarbari Khad watershed in last two decades ; (ii) mapping of LULC changes; and (iii) to interpret and analyse the LULC changes.

Review of literature
In last three decades, a large number of research works have been conducted to understand LULC changes, its drivers and impact on natural and cultural landscapes. In such studies scholars have efficiently used geospatial techniques to analyse land use/land cover dynamics. Gardner (2002) examined the linkages between deforestation and hazards in the Kullu District of Himachal Pradesh. He pointed out that the Himalayan region is prone to hazards like floods, landslides, soil erosion and debris flow. The study concluded that population growth and economic development, particularly since 1990, have enhanced vulnerability to hazards. Sharma et al., (2007) in their research work on land use dynamics of the Chabri watershed of Himachal Himalaya pointed out that the fast pace of economic, technological and institutional changes has adversely affected the resource base. They concluded that agriculture, horticulture and forestry are the main stay of Himalayan watershed economies. The main finding of research was related to changes in cropping pattern, from foodgrains to floriculture. They suggested that off-farm employment, intensive farming and scientific management of forest cover are key for sustainable development. Shah and Sharma (2015) studied the land use change in Solan Forest Division of Himachal Pradesh to assess species-specific spatial changes. They highlighted the role of remote sensing in understanding the human activities and ecological conditions in diverse landscapes of Himachal Pradesh. The study revealed increase in area under monoculture horticulture cash crops at the cost of decrease in diverse forest cover. Thakur et al., (2018) on the basis of multi-temporal satellite data analysis detected the changes in LULC for 26 years  in middle Himalayas of Himachal Pradesh. The study pointed out that increase in the agricultural, horticultural and other anthropogenic activities are at the cost of decline in forest cover and grassland. Rapid urbanisation as a consequence of tourism and depletion and retreat of snow cover due to climate change were pointed out in research findings. The study also underlined the significance of remote sensing and GIS in LULC changes detection and sustainable development of resources. Vishwa et al., (2013) in their study on Land use/ cover change and its implications for Kullu district of Himachal Pradesh, India concluded that between 1972 and 2005 significant land use/ cover changes have occurred. These changes are manifested mainly in decreasing permanent snow cover, forest degradation (in terms of forest cover density). They noticed land use changes in terms of expansion and intensification of horticulture and expansion of settlements and other built-up areas. They also linked these LULC changes with enhanced vulnerability of area to natural disasters. Kaushik et al., (2018) in their study of the Bhaga Basin glacier of Himachal Pradesh concluded that due to climate change the small glaciers at lower elevations are receding at a much faster rate. Further, they pointed out that if the present trend of glacier retreat continues, a long-term loss of fresh water storage is predicted to be dramatic. Vaidya et al., (2018) in their study assessed land use land cover changes in Kullu Valley of Himachal Pradesh on the basis of geospatial analysis of data from 1989 to 2016. The findings of their study indicated that the built-up area and area under orchards has increased significantly in the study area. The shift in cropping pattern was from traditional food crops to cultivation of vegetables and fruit crops. They concluded that increased economic returns and climate change are the probable drivers for the LULC changes in the valley. Negi and Irfan (2022) in their research work on land use/cover mapping and change detection in Upper Kullu valley, Himachal Pradesh used remote sensing technique for analysis. They concluded that in recent decades (1991 to 2020) the study area experienced significant land use/cover changes due to urbanisation, commercial agriculture and tourism. They recorded decline in area under snow cover and forest cover and increase in barren land, horticulture land and built-up area.
Thus, the review of literature reflects that LULC changes trends and consequent ecological problems have intensified in this part of Himalayan region, especially in the last three decades. These studies and keen personal interest of research scholars in addressing the emerging ecological problems due to LULC changes in the Sarbari Khad watershed and to suggest watershed specific solutions are the reasons for selection of this watershed as study area. The review of literature indicates that anthropogenic interventions have increased the ecological sensitivity of watersheds of the Himachal Himalayan region.

The area of study
The Sarbari Khad watershed of the Beas River Basin has been selected as the study area. The fast pace of ecological degradation due to enhanced population and livestock pressure has attracted the attention for detailed research work in this part of Himalayas. The land use and land cover changes due to anthropogenic interventions have increased the ecological sensitivity of this fragile watershed. The expansion of infrastructural facilities has increased vulnerability to soil erosion and landslides.
The watershed occupies an area of 930.30 Km 2 . The Sarbari Khad Watershed covers western part of the Kullu district. This watershed comprises of 13 villages in the Kullu and Nagar revenue blocks. They are Pichhbhar, Bath, Bastori, Bhalyani, Dughilag, DunkhriGahar, Gahar, Gramang, Majhat, Mashna, Peej, Phallan and Pichhli. The watershed also includes some parts of Kullu town. Total population of the watershed is 15247 people (DCHB, 2011). The main economic activity of the people here is agriculture (Gardner et al., 2015). Tourism is also an important economic activity in the study area (Gardner et al., 2015;Kumar et al., 2022).As a natural region Pir Panjal Range and Beas River bound it. The altitude varies from 1200 to 4000 m above mean sea level and it increases from south to north. The land cover of the area broadly includes snow cover, barren land, pastures and forested valley. The climate ranges from sub-tropical to alpine. The mean annual temperature in the region ranges from mild in summers and cold in winters. The watershed in located in the area receiving heavy precipitation. Precipitation occurs in this area throughout the year. The summer season receives rainfall from monsoon and the winter rainfall and snowfall occur owing to western disturbances and storms Fig. 1

Materials and method
The analysis is based mainly on secondary sources of data. The land use / land cover map derived from the National European Space Agency satellite images of Sentinal-2 of November, 2021 and LandSat-7 image of November 2000 (Table 1). The multi-temporal satellite imageries pertain to November when the area is cloud free and snow cover is minimum. The resolution of the images is 10 and 30 m respectively. This spatial resolution images do not provide scope for micro level analysis; therefore, the analysis is limited to broad classes only. The analysis was done using digital image processing software ERDAS IMAGINE 2015. For the interpretation process, Survey of India topo sheets was referenced and used. The study area boundary derived from the Survey of India topographical map and digitized in GIS environment using ArcGIS 10.8 software. The satellite images were stacked in different bands to produce a false color composite (FCC) and extracted the study area by sub-setting the image and enhancing the spectral differences of different objects. The satellite images of this area have some limitations and they lead to incorrect classification especially due to steep slopes and associated shadow areas. To reduce these errors Normalized Difference Vegetation Index (NDVI) method was applied. The FCC image was classified into seven land use categories, which extend over a

Change detection technique
After downloading the satellite imageries, the images were improved spectrally and radiometrically during the pre-processing period using ERDAS Imagine 2015. After that those improved images were used for supervised classification using the maximum likelihood classifier (MCL) technique, with signatures gathered using the spectral response pattern of each land cover class as a reference. The density slicing technique was also used to capture the threshold pixel of a few classes. In next step both the classified land use/land cover images were overlapped to determine pixel-based changes in the mainland cover classes. Then, both images were also compared in arc map using the raster calculator. After converting the raster LULC images into the vector, changes in Land use/Land-cover classes were evaluated utilizing vector data analysis techniques such as union, intersect, and symmetrical difference. In the following part this research methodology to detection of land use and land cover dynamics is elaborated in a broader perspective.

Land use and land cover classification technique
The satellite images were processed appropriately and classified for LULC change detection. The maximum likelihood technique for supervised classification was used in the present study as it is the most popular approach for analyzing remote sensing image data According to Jensen (2005) it requires a collection of firsthand observations, aerial image interpretation, map assessment, and field survey to recognize and locate land cover types that are pre-defined. It is based on the notion that the allocation of pixel values in each class is roughly characterized by a normal distribution whose parameters are digital values in each of the image's spectral bands. In general, most of a class's training pixels possess identical properties and are thus grouped in an extended cluster across space. The number of training pixels with the same value reduces as the distance from the cluster's center grows. When categorizing unknown pixels, the Maximum likelihood classifier algorithm (MLCA) considers the grouping's variability and covariance, as well as the spectral response outline. Land utilization and land cover maps for the years 2000 and 2021 were created using these techniques for seven classes depicted in Fig. 2. After making categorization, a post-processing procedure was employed.
Post-classification techniques enhance the outcome and support us in the verification of our findings.
To complete the post-processing stage, the current effort included class recoding and accuracy assessment was prepared. The recode option assigns a new class value number to any or all classes, resulting in the creation of a new thematic raster layer with the new class numbers. The accuracy assessment helps us to compare specific pixels in the thematic raster layer to known-class reference pixels. This is a method for comparing the classification to ground truth data that is well-organized.

Analysis and discussion
The LULC statistics show that in the Sarbari Khad watershed forest cover and agricultural land uses dominate ( Another significant change is increase in area under agriculture. In these two decades agriculture extension has taken place over about 457 hectare area of the watershed. With the process of socio-economic developments, the connectivity of watershed with outside world has increased. Over the period of time area under cultivation and settlements increased to satisfy ever growing demands for food and shelter. The economic advantages of horticulture especially apple orchards intensified the process of deforestation The watershed is attractive place for tourists. Over the period of time due to increased connectivity by roads, expansion of hotels and other infrastructural facilities the burden of tourists on local resources has increased exponentially. The population growth and tourist requirements have resulted into increase in area under the category of buildup area and settlements. The expansion of buildup area, especially road network, has increased the landslide hazard vulnerability in the watershed. All these anthropogenic interventions are reflected in the form of land use/ land cover changes (Table 2).
It is noteworthy in the LULC changes that the area under snow cover has declined during these last two decades . This change is not directly linked to local factors. Many studies have reported similar findings for this Himachal Himalayan region and some of them are already pointed out in the review of literature. About over 246 hectare area retreat of snow cover occurred from 2000 to 2021 in the watershed. The study by Negi and Irfan (2022) has also detected decline in area under snow cover in the Kullu valley region of Himachal Pradesh. This change is mainly a consequence of process of global warming or climate change. The consequences of this land cover change are to be faced by the locals in the form of long-term water insecurity and increased soil erosion, avalanches and risks of Glacial Lake Outburst Floods (GLOF).
The LULC changes analysis shows that in the 2000 (Fig. 2) about 3.39 per cent and 13.98 per cent of the area was under snow cover and barren/ rocky surfaces, respectively. The snow cover has reduced by 40.07 percent in 21 years whereas the rocky/barren land also reduced marginally (3.21 per cent) during this time (Fig. 3). These changes were also noted during the field work while doing interviews and field visits in the area. This transformation is mainly due to increase in area under agriculture land and infrastructure. It is noteworthy that the area under agricultural land use and settlements increased 9.38 per cent and 49.68 per cent respectively during the last two decades. The changes are due to the development of horticulture and expansion of orchards in this area. Change in settlement area is immense due to the development of tourism industry, expansion of local infrastructure and construction of hydro power project (Tucker., 1982). Therefore, the built-up area has increased and got scattered in various parts of the watershed (Fig. 4).
The pressure of human activities on available natural resources can also be anticipated by the rapid increase in number of hotels. This indicates the amount of pressure on local land resources. Beside this, the hydro-power projects have also become operational in this area over the period of time. These changes of past and intensifying anthropogenic interventions of present indicate that in future also the dynamics of LULC will go on to increase the vulnerability of fragile ecosystem of this watershed. Therefore, proper land use planning according to  land capability classes is required to achieve the goal of sustainable development. In this study focus was on macro and meso level changes in LULC changes in the watershed. The future studies should focus on micro changes, such as, to understand impact of climate change not only on snow cover retreat but also on biodiversity of the watershed. A multi-disciplinary team of researchers can contribute in suggesting site-specific solutions for integrated resource management in the watershed. This LULC dynamics is due to anthropogenic activities such as expansion of agriculture, especially horticulture, settlements and infrastructure. The most important ingredients of this LULC dynamics are the expansion of horticulture and tourism activities (Singh & Dev., 2011;Chakraborty et al., 2009). These changes have intensified the ecological imbalances in this fragile watershed of the western Himalayas (Chandel & Brar., 2010b, 2011a, 2011bChandel & Brar., 2010a).

Conclusion
Land Use/Land Cover changes are common processes caused by anthropogenic and natural factors. Accelerating population and goal of economic growth are the major drivers of these changes in the Sarbari Khad watershed, in the last two decades. The Himalayan watersheds are very fragile and LULC changes have intensified the challenge of their stability and sustainability. The demand for land for settlements, agriculture and developmental activities such as construction of roads, dams and power projects, tourism and associated infrastructure have led to changes in LULC and the associated short-terms gains have reduced the long-term carrying capacities of the Himalayan watersheds. The present study like many other research works of the Kullu Valley region confirms that the area under forest cover has declined and the quality in terms of density and diversity of natural vegetation has also degraded especially in last two decades. The area under cultivation has increased and cropping pattern has shifted from traditional foodgrains to cash crops and horticulture. Area under built-up and settlements categories has also increased mainly to fulfill the demand of rising population and economic activities such as tourism and infrastructural developments. The study highlights that the area under snow cover has significantly declined in last two decades mainly due to climate change which involves global interlinkages instead of local interferences. These LULC changes should be addressed by designing and implementing appropriate resource management policies. This study also proves that integration of GIS and remote sensing technologies with traditional data base is an effective tool for change detection and ultimately for providing data base for sustainable watershed management.

Declarations
Conflict of interest All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.
Ethical approval This research did not contain any studies involving animal and human participants, nor did not take place on any private or protected area. No specific permissions were required for corresponding locations.