Development of Catchment wise Integrated Drainage System through Remote Sensing and GIS towards solving Waterlogging at Macro Level – A Pilot Area Study


Er. P.K. Bordoloi
Tocklai Experimental Station
Tea Research Association
Jorhat, Assam - 785008


Er. Dipankar Borah
Tocklai Experimental Station
Tea Research Association
Jorhat, Assam - 785008

Dr. A.K. Dutta
Tocklai Experimental Station
Tea Research Association
Jorhat, Assam - 785008

Abstract
Flooding and waterlogging in the tea plantation of the Brahmaputra plain, soil erosion and landslide on the hilly tea plantation of Darjeeling disctrict and hillocks in the Barak valley, spate flooding, gully formation and river erosion in the foothills plantation of the great Himalayan foothill and Terai areas have been a cause of concern for the tea industry of the North Eastern region of India. The industry in the region accounts for 55% of total Indian production of tea and about 250 million Kg in average per annum is being exported earning valuable foreign currency. Excessive summer monsoon rainfall in the region and the nature of terrain over tea is grown give rise to storm water management problem as stated above. GIS technique is being used on pilot area basis as a diagnostic tool for analysis of the problems. This paper discusses the application and util;ity of this tool in ameliorating storm water management problem faced by the tea plantation of North Eastern Region of India

Introduction
Water management is an important factor for augmenting productivity of a perennial crop like tea. Due to heavy rainfall in the monsoon months and subsequent soil moisture stress in the wintry rainless periods, tea bushes suffer from the twin menace of - (a) excess soil moisture in summer monsoon and (b) drought in the winter. Apart from these, geo-morphological changes in river basin results in rise of drainage base and thereby increasing the problem of water-logging. Most of the problems are area specific.

To identify and address the water management problems of tea growing areas of the North East, a pioneering effort was made through the present project by TRA under the 10th plan. Tea industry is a pioneer in the country in respect of agricultural land drainage. It is alive to the problem since the ‘50’s and has been unceasingly making efforts both in the research front and in the absorption of research results. Even though the efforts have been bearing fruits, never the less, much more is needed to be done to save the valuable crop from the harmful effect of waterlogging and to ensure sustained productivity as well as to protect the tea land from being flooded and eroded. Water follows catchment for movement and hence one cannot tackle the problems relating to water in isolation – and they entail the concept of watershed development. Watershed development in its term involves multidimensional issues and priorities. Therefore, for setting one groups priority as the foremost one needs to have a precise diagnostic tool to identify the problem in the entirety conforming to watershed concept in proper perspective. For that matter one need to have topographic information at catchment level inclusive of drainage network – the drainage density. The major objective is to find existing status of natural drainage network of the study area and the extent of drainage Impediment in catchment level. Remote sensing technique by virtue of its synoptic view, repetivety and cost effectiveness in viewing the inaccessible areas was utilized. GIS, a computer based model for storing and retrieving geographical data was used to build the database of the tea gardens. For this purpose, five pilot locations – Tingrai basin of Upper Assam, Madhura basin of Cachar, Nonoi basin of North Bank, Dooars region and Chota Rangit watershed of Darjeeling were identified to represent the excessive water disposal problems specific to the respective areas. At present, required information for three areas covering an extent of 1137 sq. km that included 75 tea gardens have been completed and works on other two areas are progressing fast.

Materials and Methods:
To identify and address the water management problems of tea growing areas of the North East, the present project was undertaken. The major objective was to find existing status of natural drainage network of the study area and Drainage Impediment in Catchment Level. For this purpose, five pilot locations – Tingrai basin of Upper Assam, Madhura basin of Cachar, Nonoi basin of North Bank, Dooars region and Chota Rangit watershed of Darjeeling were identified to represent the problem of excessive water disposal. LISS III sensor data of 23.5m resolution were used for all the study areas with Indian remote sensing RESOURCESAT satellite obtained from NRSA. In two areas MONO data of 5.8m resolution were used. Investigations on Tingrai basin of Upper Assam, Madhura basin of Cachar and Nonoi basin of North bank have been completed. Various maps such as Drainage, Slope, Soil erosion status, Geomorphological maps etc. were prepared for respective areas from satellite images and other lateral information, which were again verified on the ground. The methodology adopted were – a) data procurement, b) base map preparation, c) preliminary interpretation of RS data, d) ground verification and field information, e) final map preparation. Base maps showing major river courses and other important information like tea garden boundaries, roads & railway line etc. were prepared. Collateral information like Survey of India toposheets, geological information etc. were collected and field verification was carried out to match the results after visual and digital interpretation of satellite imagery. Finally, various theme based maps such as drainage, soil erosion were prepared along with detailed reports.

Results and Conclusion :

Tingrai basin, Upper Assam



During the firstt phase work on Tingrai basin of upper Assam was completed. Details of the work done undertaken including location map, Number of Tea Estates covered & their Geological information, including necessary information to drainage problems & their probable solutions were incorporated in the progress report up to December’2004. Some finer aspects that were not considered earlier were identified, were incorporated with the earlier report to prepare final comprehensive recommendation plan for tingrai basin. The salient features of the report are as follows
  1. The 4th order streams where eutrophication is highest should receive priority.
  2. Based on the relief of the land, extinct stream should be restored to the original width and be deepened to 2-2.5m depths to ensure easy flow of water thereby improving the drainability of the area.


Second phase of project that included part of Cachar area was completed and report was received in April 2005. The details are as follows :
  1. The area under investigation is situated on the north-eastern part of the Cachar district of Assam covering an area of about 312 sq. km between latitudes 24°50' and 25°00' North and longitudes 92°50' and 93°00 East which is a part of flood plain of Barak river system.
  2. The study area comprise 28 tea gardens.
  3. For the purpose of investigation, LISS III Geocoded data acquired on 7th February 2004 of IRS P6 were used.
  4. Base map was prepared from SOI toposheet and field investigation was done for 4 days and details of findings were transferred on to the map.
  5. The raw image was classified to generate Land use/ Land cover and Geo-morphological map.
  6. Since the area suffers from landslides and erosion, Slope map and Soil erosion status map was prepared in GIS environment. With the help of Contours extracted from Survey of India (SOI) map, 3 dimensional view of the terrain (DEM) was created. Slope map was also prepared from the specifications suggested by AISSLUP (All India Soil Survey and Land use planning). Soil erosion status map was generated on the basis of slope and Land use/ Land cover of the area.
  7. Results show that majority of the area is under forest (115.04 sq. km) while only 19.27 %( 60.11 sq km) is under Tea. Drainage map shows that river Madhura has sifted its course in many places. Effect of Erosion of that river on nearby tea gardens is clearly seen on the map. Slope map shows that most of the area falls under very gentle slope class that are more stable compared to others. Soil erosion status of majority of the areas is low.
  8. Area for rainwater harvesting was identified from the imagery. A detailed levelling survey will be required to plan for height of the proposed bund vis a vis water spread and volume of water that can be stored.
The results obtained for the completed study areas are as follows

Tingrai basin (Upper Assam): Covered 457 sq. km, which included 35 tea estates
  1. In Tingrai area, by superimposing the current satellite image with the Survey of India map of 1970, it was found that many drainage channels have become extinct or in the verge of extinction which have ultimately resulted in severe water logging.
  2. During ground truth verification it was found that the streams are narrow and silting has taken place along with growth of vegetation at the source which ultimately resulted in decrease of flow
  3. Man made problems has been causing woes to the region.
  4. Based on the above facts a comprehensive action plan for Tingrai area was submitted to the concerned authority to tackle the problem arising out of the situation.


    5. Madhura basin: Covered 312 sq. km, which included 28 tea estates.

  5. Valuable top soil is being eroded every year. Slope map was prepared which indicated that majority of the tea estates are located in moderate and gentle slope classes.
  6. The gardens lying in northern part are very much prone to soil erosion due to steep slopes.
  7. Three dimensional water harvesting models were prepared for tea estates to find out the water volume & spread.


    8. Nonoi basin: Covered 368 sq. km, which included 12 tea estates.

  8. The area being situated in foothills suffers from heavy lateral erosion due to steep gradient and abrasive materials. Deforestation coupled with the local irrigation channels (dongs) are the major cause of erosion .In monsoon when they are in full spate erodes the banks resulting in valuable loss of tea areas.
  9. In order to fight the menace of floods and erosion, an action plan is under preparation.
The action plan for Tingrai basin is already submitted and the rest are under preparation and the work is adhering to the schedule.