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Satellite surveillance for disaster mitigation

 

V.S. Arya, B.S. Chaudhary, A.Beniwal, T.P. Babu and R.S. Hooda
Haryana State Remote Sensing Application Centre,
Hisar – 125 004, Haryana, India

Abstract
In India floods have become an unfailing annual national event causing rate havoc and extensive losses to agricultural statistics at an early stage is one of the essential requirement for effective management of flood problem and also to make the base-line information for taking preventive measures in future. Haryana witnessed severe floods during September 1995. The present study deals with mapping management of floods in Rohtak district, Haryana (India). Fifty five percent of the total geographical area of the district was inundated by floods covering three hundred villages. Heavy down pour in shorter duration, non maintenance and breaching of drain no8 and presence of localized depressions were the main causes of floods in the district. Desilting and deweeding of drain no.8, proper maintenance of embankments and construction of ring bunds around major settlements were suggested as the management practices for mitigating floods.

Introduction
In India, floods have an unfailing annual national even causing great havoc and extensive losses to agricultural crops, human life and property. The total flood affected area in 1987 was about 11.4 million hectare as compared to only 6 million hectare in 1981 (Rao, 89). Flood mapping through satellite remote sensing has been successfully carried out in India (Rammoorthy 1989, Hooda et. Al. 1995 Chaudhary et. Al. 1996) and abroad (Florezano, 1989 and Brouwer, 1996). Haryana which is one of the most agrarian State in India, has suffered from floods during the year 1995. However, during the last 40 years, efforts are being made by Central and State Governments to reduce the floods damages by taking appropriate measures. For planning the flood control and related works, reliable and timely information about flooded areas, river behavior and configuration prior to floods, during and after the floods is required. Such information is very difficult to acquire through conventional surveys. Advent of satellite remote sensing technology has helped in

solving the problem of mapping, monitoring and management of flood prone areas. Keeping this in view, the present study was carried out to map the extent of floods in Rohtak district, Haryana using remote sensing technology and to suggest management practices for mitigating flood.

Study Area
The study area that included entire Rotak district lies between 28o21′ to 29o06’N latitudes and 76o13′ to 76o58′ E longitudes. It covers a total geographical area of 3580 sq. kms. Rohtak district forms the outer of the bowel shaped topography of the Haryana state and therefore prone to floods despite low rainfalls.

Hot summer, cool winter and merge rainfall are the main climatic characteristics of Rohtak district. The average annual rainfall in the district is 457.6 mm. It generally increases towards north east About 74% of the annual rainfall is received during the rainfall is received during the monsoon season. On an average there is 24 rainy days in a year in the district.

Data Base and Methodology
The data used are given as under :

  1. IRS IB LISS II Diapositive of September 16 and 18, 1995 and LANDSAT TM diapostive bulk scene of September 24, 1995 of the area.
  2. Survey of Inda topgraphical maps on 1:50,000 scale.
  3. Other ancillary data.

Base maps were prepared on 1:50,000 scale with the help of survey of India toposheets. Visual Interpretation techniques were employed by taking into consideration various image interpretation elements such as color, tone, texture, size, shape, shadow, pattern and association. The information regarding flood affected areas from film positive had been transferred on to the base maps using PROCOM-2. Doubtful areas were verified during field visits. The area were verified during field visits. The area under each category was calculated using dot-grid method.

Results and Discussion
The flood affected areas were delineated based up on the sharp contrast between water spread and adjacent areas. Following two categories of flood affected areas were identified (Fig. 1).


Figure 1
  1. Standing water
  2. Receded Water/Wet Areas

The standing water areas appeared as dark blue to light blue depending upon the depth of water, wheras, the receded water/wet areas appeared as dark grary to light gray in tone. The vusual interpretation of the satellite imageries showed that about 196957.47 hactare area was inundated, which covers 55.01% of the total geographical area of the total geographical area of the district. The area of the district. The area under standing water comes to 60924.85 hectare i.e. 17.02% and receded water/wet area comes to 136032.62 hectare i.e. 37.99 percent of the total geographical area as on Date of satellite pass.

 

 

 

Causes of Floods

  1. Heavy Downpour
    A careful look on the rainfall data for the past three flood affected years i.e. 198,1993, 1995 indicated that the highest rainfall was received during rainfall was received during 1995 (Fig. 2). The rainfall during 1995 was concentrated in the end of August and first week of September. The rain fall observed during 28th, 29th and 30th August was 67.5, 72.0 and 62.0 mm and during 2nd, 3rd and 4th September was 86,115 and 135mm respectively (Fig. 3). Hence, this heavy rainfall within very short time caused floods in the area.


    Figure 2 Annual rainfall, Rohtak district

    Figure 3 Monthly Rainfall during 1995 Rohtak District
  2. Non-maintenance and Breaching of Drain No. 8.
    The drain No. 8 covers whole of the Rohtak district. The salutation and growth of vegetation in the bed of the drain blocked the rain water which caused breaching of the drain. This became the main reason of floods in the district.
  3. Presence of Localised Depressions

    Few localised depression in the district got flooded due to heavy precipitation. These are the low lying areas which get water logged during the monsoon season and have no proper drainage.

Flood Management
On the basis of extensive study on extent and causes of floods in the district, it is possible to suggest appropriate measure based on avove findings. But the floods can not be totally controlled it is not possible to provide protection against all magnitudes of floods. The repetition of catastrophe that had occur in the study areas can be minimized by taking various structural or non-structural measured (Ramamoorthy, 1989).

  1. Desolation and Deweeding of Dran No. 8
    The drain no-8 which was bult to drain out the excess water from the district into the Yamuna river should be desalted down to its original depth and the vegetative growth should be removed so that its actual water carrying capacity may be restored.
  2. Proper Maintenance of Embankments
    Weak points on the rivers banks should be identified and an effective technique should be adopted to re-enforce soft zones, Geotextiles not only effectively control soil erosion but also facilitate drainage and stabilize river banks. The vegetation cover can be carpeted to reduced breaching and soil erosion.
  3. Construction of Ring Bunds
    All the major settlements should be identified in the flood affected areas and should be surrounded by ring bunds to protect from floods. This will save human life, their cattle stocks and property to a large extent.

Conclusion
The study demonstrates the capability of satellite data for mapping and management of flood inundated areas. Moreover, the provides clues for effective management of such areas. Till now structural methods have been adopted for planning of flood affected area but with the advent of satellite based information system, including all weather satellites, priority may be given to non-structural methods such as disaster preparedness, relief and rehabilitation.

References

  • Chaudhary, B.S.; Arya, V.S.; Beniwal, Ashok; Babu, T.P. and Ruhal, D.S. 1996. Space Application for disaster management: Floods in Hisar, Sept., 1995. Presented in Seminar on Environmental Management – Challenges and Strategies, Hisar (India).
  • De Brouwer, J.A.M. 1994. Flood study in the meghna Dhonagoda polder, Bangladesh. Proc. 15th Asian conference Remote Sensing Vol. II pp C-7-1 to C-7-6.
  • Florezano, T.G. 1989. Flood management using Remote Sensing data. The Brazilian experienced. Space and flood management. I.A.F. 40th congress, Malaga spain, pp 31-46.
  • Hood, R.S.; Hooda, I.S. and Arora, B.K. 1995. Remote sensing based monitoring and management of floods in parts of Harya using satellite data. Proc. Intl. Conf. On Remote Sensing and GIS, Hydrabad, India. Pp. 221-225.