Post Tsunami Impact Assessment on the Coastal Hamlets in Nagapattinam using IRS P6 Data

Abstract

Nagapattinam coastal zone in Tamil Nadu is the worst affected region due to the December 2004 Tsunami. The seawater intrusion was traced from 300 meter to 3 kilometers affecting majority of the coastal communities in this district. The reports indicate that among the affected, 87 per cent of them are from fishermen community. The tsunami affected 38 revenue villages and 73 coastal habitations. Among the confirmed death, the Nagapattinam coast alone records 6065 deaths; this is 76 percent of the state’s total. The tsunami waves fattened 51 fishing hamlets and affected the permanent and temporary constructions, boats and catamarans, fish landing and auction centers and destroyed marine machines and freezer plants. Large-scale damages were reported due to the coastal sand inundations and seawater intrusions. The present study is to assess the post-tsunami impact on coastal hamlets selecting three highly devastated coastal hamlets of Nambiyarkuppam, Akkaraipettai and Keechankuppam. To study the post-tsunami impact, IRS P6 data were used.

Introduction

Tamil Nadu was the worst affected state in India during tsunami in December 2004, with a death toll of about 8000 people. All thirteen coastal districts of the state and the Union Territories of Pondicherry and Karaikal were affected and the worst losses occurred in Nagapattinam district where more than 6,000 people were killed. An estimated 85 percent of people affected by the tsunami in Tamil Nadu are believed to be from the fishing community. Tamil Nadu has 591 fishing villages and 362 fish landing centres, which are mostly small and cater to the needs of small mechanized fishing crafts and traditional boats. The fisheries sector has suffered major damage in terms of lives, boats, and gear and to the infrastructure such as harbours and fish landing centres. Fishing activity in Kancheepuram, Cuddalore, Thiruvallur and Nagapattinam has not still recovered fully. Tamil Nadu's fishing community is a significant contributor to the state economy with marine fish landings estimated around 380,000 tonnes per annum. About 58,000 tonnes of seafood valued at about 480 million U.S. dollars is exported annually from the seafood processing units located in the state.

Problem

The impact of the Tsunami waves was unknown to Indians until the morning of the 26th of December. Nagapattinam was the worst hit with the death toll of 6065 people, and several others are missing. Even after ten months, time the coastal village of Akkraipettai in Nagapattinam still looks like a ‘noman’s land’ as its causeways to the mainland were washed away. The December tsunami had washed away almost all the temporary structures in Akkaraipettai and Keechankuppam the fishing hamlets on the Nagapattinam beach. The permanent constructions were destroyed partly and recovery is possible only when heavy financial help is made available. Temporary bridges are being constructed using debris on site to begin the fish trade.

Objective

The present research has been carried out with an aim to study the impact of tsunami over the three adjacent coastal villages of Nambiyarkuppam, Akkaraipettai, and Keechankuppan using IRS P6 digital data. This micro-level analysis of impact assessment will help the field workers and the administrations to work out the recovery strategies. The present study assesses the damages caused to the physical and cultural features in Nagapattinam coast zone and also to study the impact at micro level by selecting the worst affected three coastal hamlets of Nambiyarkuppam, Akkaraipettai and Keechankuppam through the image analysis of remote sensing digital data. The study records the damages caused in terms of seawater intrusion, low lying area, sand inundation levels and in the Nagapattinam coast zone.

Methodology

To analyze the impact of tsunami along the Nagapattinam coast, three worst affected fishing villages of Nambiyarkuppam, Keechankuppam and Akkaraipettai were selected. The IRS P6 digital data were procured from the NRSA for the pre (18-12-2004) and post (6-1-2005) tsunami periods and subjected to various digital image analyses to assess the damages caused to the physical and cultural features for the Nagapattinam District as a whole at micro-level. For digital image processing analysis supervised classification of spectral angle mapper of Envi 4.1 was used to derive the results. The selected villages are just within 100 m away from the coast. The general analysis performed to the entire Nagapattinam coast shows a large scale damage of physical landscape have been changed from pre to post tsunami periods. Specific analysis is made, selecting three areas in the study area, Zone A (Nambiyarkuppam), Zone B (Keechankuppam) and Zone C (Kallar and parts of Akkaraipettai).

Image Analysis

The image analysis, comparing the pre and post tsunami, gives the extent of sea water intrusion levels, sand inundation levels, coastal huts and settlement damages and dumping of boats and fishing materials. The general image classification indicates the shifting of sands in the coastal surf zone due to the impact of turbulent and violent waves in different direction.

Table – 1 Pre and Post Tsunami Conditions along Nagapattinam Coast
Features	Pre-Tsunami Area in Sq.m	Post-Tsunami Area in Sq.m	Difference
Settlements	388231	715716	327485
Costal Huts	1367923	1320982	-46941
Vegetation	1407685	715163	692522
Wet Land	669327	327484	-341843
Sand spread	550593	699148	148555
River Water	314782	797449	482667
Inland Water	156286	75106	-81180
Sea Water	688655	592564	-96091

Table 1 and Plate 1 show the general conditions of the pre and post-tsunami along Nagapattinam coast. Coastal situations are classified as the coastal huts, settlements with thatched sheds/ metal sheets, vegetation cover along the coast, wet land conditions, sand inundation levels, sea water intrusion levels, widening of river mouth and inland water areas, to notice the damages due to tsunami waves. The settlements along the coast were reduced and the debris of the settlements were thrown out by the violent waves and got deposited over the existing settlement regions a little away from the coast. Similarly the coastal huts, the temporary shelter for the fishermen communities were severely affected, and they were also carried away along with boats and shattered debris above the existing settlements that downloaded the debris thus carried away. From the Table 1, it is noted that area under settlement increased after tsunami; it may be becuase during the post tsunami period the debris of settlement and the coastal huts were added with the existing settlements. Nearly 50 per cent of the vegetation cover has been wiped away. Half of the wetland has been reduced and covered with sand particles washed by the turbulent waves. Coastal sand has been pushed back and a clear demarcation of sand inundation layers is present. Inland water areas as well as replacement of seawater in the river feature are also visible in the processed image. Sea water intrusion is significant particularly wherever there is river feature and the level of intrusion is very high which is shown in the image.

In Nagapattinam, the severely affected areas are Nambiyarkuppam (Zone A), Akkaraipettai, Keechankuppam and parts of Nagapattinam (Zone B) and Kallar (Zone C). They were specifically subjected to digital image analysis because of its vulnerability in the context of tsunami. A field investigation on 28th December 2004 substantiates the results of the digital image analysis, and it is presented in Table 2 to 4.

Table – 2 Pre and Post Tsunami Conditions in Nambiyarkuppam
Features	Pre-Tsunami Area in Sq.m	Post-Tsunami Area in Sq.m	Difference
Settlements	45284	151316	-106032
Costal Huts	340738	562190	-221452
Vegetation	704671	199914	504757
Wet Land	141376	57434	83942
Sand	49702	146898	-97196
River Water	65165	340738	-275573
Inland Water	88912	11045	77867
Sea Water	112659	57434	55225

In Nambiyarkuppam the debris of settlement caused by tsunami waves increased the area of settlements by more than 100,000 sq. m. The coastal huts swept by the surging waves got strewn across an area of about 220,000 sq. m. Vegetation cover in this part has been reduced to nearly 70 per cent. The wet land areas got reduced by about 40 per cent. Sand spread was increased in area by about three times that of prior to tsunami. The river mouth (Plate 1) got widened during tsunami, and this facilitated large quantity of sea sand to travel far inside the land along the river water ways, and this also resulted in wide spread sea water intrusion.

Table 3 Pre and Post Tsunami Conditions:Akkaraipettai and Keechankuppan
Features	Pre-Tsunami Area in Sq.m	Post-Tsunami Area in Sq.m	Difference
Settlements	4970	51359	46389
Costal Huts	493711	404799	-88912
Vegetation	368903	284961	-83942
Wet Land	333006	159048	-173958
Sand	194392	215929	21537
River Water	142480	284961	142481
Inland Water	38105	34791	-3314
Sea Water	195496	174511	-20985

In Plate 2, Zone B parts of Nagapattinam town and two major fishing hamlets of Akkaraipettai and Keechankuppam and the connecting bridge between Nagapattinam and Akkaraipettai are found located. Near the connecting bridge fish landing center is housed and the entire area was disfigured. The boats were twisted by the violent tsunami and transported to long distances and deposited on the roads and the railway tracks near the railway station of Nagapattinam. The tsunami hit the Nagapattinam coast at about 8.30 am on Sunday, the 26th December 2004 when the fishermen were just arriving from the sea and transacting their catch with traders, who were waiting in the Akkaraipettai fish landing center. The tsunami swept the men and materials and deserted the whole area in a few minutes. The image analysis indicates that the entire hamlet was shattered and its permanent and temporary settlement debris got scattered all over, upto 1 km from the coast. Ares occupied by the coastal huts got reduced by about 50,000 sq. m. The vegetation cover got declined to about 234,000 sq. m. But the sand spread was increased. The tsunami broadened the river mount and coastal sands were carried for long distance upstream. Sea water intrusion is seen all along the river mouth zones and to a distance of about 2.5 km upstream.

Table 4 Pre and Post Tsunami Conditions : Parts of Akkaraipettai and Kallar
Features	Pre-Tsunami Area in Sq.m	Post-Tsunami Area in Sq.m	Difference
Settlements	0	17672	-17672
Costal Huts	222556	172854	49702
Vegetation	346813	234154	112659
Wet Land	230288	161809	68479
Sand	131987	135301	-3314
River Water	97196	209855	-112659
Inland Water	23194	23194	0
Sea Water	50807	93330	-42523

Zone-C includes parts of Akkaripettai and up to Kallar. Large volumes of coastal sands were carried by the tsunami waves along Kallar River and got deposited along riverbeds and also in the wetland areas of the pre-tsunami periods. In this zone too, a majority of the coastal huts were uprooted by the turbulent waves and strewn in the leeward side. Vegetation cover has been reduced from 0.34 to 0.23 sq. km in area. This area did not contain any settlement zones during the pre-tsunami time period. The seawater intrusion was noticed all along the Kallar river, and area affected in this way got increased from 0.09 to 0.20 sq. km in area.