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In-depth assessment and analysis of the environmental effects of Tsunami and assistance Post-Tsunami support and damage assessment for understanding and future course of action
In-depth assessment and analysis of the environmental effects of Tsunami and assistance Post-Tsunami support and damage assessment for understanding and future course of action 4.1.2.1 Support through computerized identification of victims and reuniting separated family members Tsunami offered the rarest of opportunities to study and understand a natural clamity that affected the coastal ecosystem and the human activities along the east coast enormously. As a responsible national facility, our scientists were at the site not only for collecting valuable samples, specimens and do various measurements but also help the victims through information technology to find their kith and kins, separated by the sudden disaster. The specific activities and projects carried out are given below. Tsunami was an unexpected human tragedy, which required integrated support through this Centre. This Centre could rise to the occasion by organizing teams immediately after the news and sent them in its vehicle to visit the affected sites and aid in the identification of victims and reuniting separated family members. The team spent 10 days at Nagapattinam. A web based solution by name e-milan was developed which enabled the �Lost� and �Found� persons to be reunited by posting their photograph and other details on a centralized server that can be accessed from anywhere using a modem and a phone line. The Government and the public hugely appreciated this effort. 4.1.2.1. Tidal impact on water quality assessment and sediment characteristics in Tsunami affected Andaman Islands This study is based on the after effects of the December 26, 2004 Tsunami, which struck the Andaman and Nicobar Islands and Tamil Nadu in the mainland India among many other Indian States and nations. Rapid environmental assessment with respect to changes in tidal height, influence of changes in tidal height on water quality, distributional pattern of dissolved oxygen, turbidity, chlorophyll and profiles of temperature and salinity under the changed scenario was undertaken. The data were compared with previous study performed by the Institute of Ocean Management; Anna University in these affected areas to highlight the intensity of change if any, due to tsunami. A detailed physical survey in addition to monitoring the changes in surface water characteristics after the tsunami was made. Surface water samples (post-tsunami) were collected from both the mangrove and coral reef ecosystems of Andaman islands, during both dry and wet season from 9th -15th April, 2005 (dry period) and from 17th -23rd August, 2005 (wet season). Sampling was done both in the South and North Andaman Islands. In South Andaman surface water samples were collected from two different spatial transects. From each spatial transect 15 different samples were collected, one arm extending from Wandoor to Chidiatapu, towards Bay of Bengal and the other from Wright-Myo mangrove creek to towards the Andaman sea. Also tidal study was conducted for 24 hours and surface water samples were collected each hour in a small tidal creek at Wright Myo (11� 47� 27.7� N, 92� 42� 24.3� E) of 8km long and 50m wide that is flanked by dense mangrove vegetation dominated by Rhizophora sp., and also surrounded by hilly, terrestrial vegetation coverage. Similarly, in North Andaman sampling was collected in two different spatial transects i) extending from Mayabunder to Kalighat creek towards the Andaman Sea and ii) from Mayabunder to the North reef in the Bay of Bengal. Sampling was made for a full tidal cycle (24 hours) in the Kalighat creek (13� 07� 29.2� N, 92� 56� 48.1� E), which is 50m wide and almost 10km length. Like Wright Myo, the Kalighat creek is also quite thickly vegetated mangrove environment and is very sparsely populated. Spatial variation in tidal amplitude and water quality: Assessment of the surface water showed extensive, but uneven, damage to the natural resources that acted as the first line of defense from the tsunami, such as coral reefs, mangroves, sand dunes and other coastal ecosystems. Anecdotal evidence and satellite photography before and after the tsunami event seem to corroborate claims that coral reefs, mangrove forests and other coastal vegetation, as well as peat swamps, provided protection from the impacts of the tsunami. The damage to coastal ecosystems is highly variable, and the damage to coral reefs is mostly due to the sediment accumulation due to the turbulent churning of the sea. Coastlines have been eroded, with much of the sediment deposited on healthy reefs, agricultural land, creeks, or even creating new islands. Shallow soils were stripped from some low-lying atolls. The tsunami caused significant geomorphologic changes along the coastline, such as eroding sand beaches and enlarging water channels. Post-tsunami studies have confirmed extensive changes in coastal geomorphology for the Andaman Islands. In North Andaman, change in tidal amplitude was even more remarkable than in South Andaman. Post-tsunami data were compared with the existing records for pre-tsunami and found large variations as a result of the massive changes in geomorphology of the island. Some of the possible reasons include: � Changes in amplitude or phase of shelf internal tides, altering surface tides: This may occur because of warming at the surface or at depth, increasing or decreasing stratification. Reduced freshwater discharge may also decrease stratification � Changes in estuarine processes: Decreased bed friction (due to reduced river flow and sediment transport), channelization (reducing friction), and shoreline alteration (which usually reduces area and volume and funnels the tidal wave) may increase tidal amplitudes. Clearly, tectonic changes ave altered tides. Differences in water height based on our observations and predicted (tide table) levels Tidal variation of dissolved trace gases and nutrients The means and ranges of dissolved CH4 and N2O concentrations during January 2004 (pre-tsunami data) (dry season: mean CH4 491 � 133.04 nmol l-1, range 282-704 nmol l-1; mean N2O 9.0 � 2.34 nmol l-1, range 6.0-13.2 nmol l-1) varied significantly from those during April 2005 (post-tsunami; wet season: mean CH4 392 � 64.0 nmol l-1, range 198-585 nmol l-1; mean N2O 4.8 � 1.32 nmol l-1, range 2.7-6.9 nmol l-1 N2O), and we observed a discernable trend in CH4 or N2O after the tsunami in South Andaman. The waters of the mangroves in South Andaman have therefore shown a significant effect of the tsunami by diluting the concentration of CH4 and N2O after the event. Parameters January 2004 April 2005 / August 2005 Difference High tide Low tide High tide Low tide Water Height (cm) 150 80 265 -70(April 2005) +115 cm (August 2005) Salinity 30 20 34 28 17 01 +4.0 -2.0 -3.0 +19.0 DO (mg/l) 2.4 4.3 4.9 6.4 +2.5 +2.1 TSM 31.8 19.2 28.4 453 -3.4 +434 NH4(�M) 4.2 8.7 150 500 +144 +492 NO3 120 380 0.432 13.98 +260 +13.5 NO2 5 20 0.102 0.459 +15.0 +0.35 pCO2 (ppmy) 1868 6407 NA CH4Conc. (nM) 282 704 198 585 -83.6 -119 N2O (nM) 6 13.2 2.67 6.89 -4.33 -5.23 Comparison of CH4 emission in surface water of mangroves in April 2005 and August 2005 in South Andaman The waters surrounding the mangroves prior to the tsunami have been a strong source of CH4 and a weaker source of N2O to the atmosphere throughout the year. But after the event, there has been significant inundation of sulfate-rich waters thereby suppressing the CH4 emission to the armosphere. During January CH4 and N2O were more strongly correlated with tidal elevation (r2 = 0.84 and 0.94 respectively) than with salinity (r2 = 0.8 and 0.88). Furthermore the observed salinity range during the dry season (20-27) was smaller than during the wet season (0-28) suggesting dilution is only a secondary factor influencing the observed concentrations of dissolved CH4 and N2O. The pre-tsunami dry season (January 2004) data indicates that NH4+ accounted for a small fraction of the total inorganic nitrogen species in the surface water. After the December 26, 2004 event, the concentration NH4+ increased by an order of magnitude from 5�M to 500 �M indicting intense nitrification of the system. About 90% of dissolved inorganic nitrogen (DIN), was composed of NH4+ as observed in other mangrove environments [Nixon et al., 1984; Dittmar, 1999], and in our earlier studies for the same ecosystem. NH4+ in surface water of mangroves in April 2005 and August 2005 in South Andaman Concentration of Dissolved Oxygen in surface water of mangroves in April 2005 and August 2005 in South Andaman Concentration of Dissolved Oxygen in surface water of mangroves in April 2005 and August 2005 in South Andaman Surface water salinity of mangrove waters in April 2005 and August 2005 in South Andaman The observed change in DIN speciation after the tsunami is consistent with an increased flux of NO3- to mangrove waters from freshwater after the event. Alternatively, increased nitrification activity resulting from outwash has led to an observed increase in oxidized nitrogen. Figure 4 shows a temporal progression of maxima first in NH4+ concentrations (at the hourly sampling resolution) consistent with their sequential oxidation. This is indicative of increased nitrification activity within the mangrove system as NO2- is a highly transient species and unlikely to be reflected in terms of increased freshwater inputs and therefore is a result of the tsunamigenic activity. Temporal changes (prior to and after the tsunami) in NO3- and NH4+ closely followed those of dissolved gases and mirrored those in tidal elevation and salinity, implying strong tidal control for all of these variables in the mangroves of the South Andaman. The dissolved oxygen content for the two surveys were not largely different although lower concentrations were seen in the wet season, which may be a reflection of continued reduced oxygenated conditions because of the standing water even long after the tsunami had occurred. Similar observations were made for salinity of the surface waters, where significant change between the dry and wet period was not discernable. Geochemical investigations of Tsunamigenic sediments: Geochemical indicators, such as major element enrichment (Na, Cl, S, Br etc), have been used to indicate a marine source for the deposit. When sediment is deposited by a tsunami and preserved, a geological record of that tsunami is created. Analysis of major and trace element variations unrelated to human activity in the sediment column indicates that except for near-surface perturbations (0-10cm), major compositional breaks are limited to lithological transitions. Reinhart (1991) argues that in protected tidal channels, storms are unlikely to suspend the volume of sediment necessary to produce the deposits observed. When layers are present, their number and thickness are sometimes used to differentiate between a tsunami and storm deposit (Williams and Hutchinson, 2000). From the results several features in major element chemistry suggest a role for deposition of tsunamigenic sediments. Ca and Sr gradients show surface enrichment and much lower K. Surface enrichment of Na, Cl in mangrove and adjacent agricultural land after the December 26, 2004 Indian Ocean tsunami All the major elements in particular, Si shows an anomalous increase at depth between 6 and 8 cm in the mangrove cores and in the adjacent agricultural area, which indicates sediment deposited as a result of the tsunami. Another important element P shows a distinct depletion, while sulfur (S) shows enrichment at the same depth (6-8 cm) in both the mangrove and agricultural sites. Similar enrichment of major elements was observed in the mangroves of Wright Myo and the coral reef site of Redskin Island. The mangroves of Wright Myo Creek have not been affected by the December 26 tsunami, while the coral reef of Redskin Island has experienced large-scale degradation. Surface enrichment of Si, K in mangrove and adjacent agricultural land after the December 26, 2004 Indian Ocean tsunami Surface enrichment of P, S in mangrove and adjacent agricultural land after the December 26, 2004 Indian Ocean tsunami Surface enrichment of Na, Cl in Wright Myo mangrove and Redskin Island Coral Reef after the December 26, 2004 Indian Ocean tsunami The mangroves at Wright Myo have protected the shoreline from the giant waves and the only effect of any destruction of the surrounding areas is as a result of the subsequent aftershocks. In the Redskin Island however, corals have been tossed and turned upside down uprooting them. Even after months after the tsunami, the surface water in Redskin Island, overlying the coral reef area remained turbid with a heavy suspended sediment load. Results from the sediment profile reveals this disturbance showing a surface enrichment of all major elements such as Na, Cl, Fe, Mn in addition to others. Surface enrichment of Fe, Mn in Wright Myo mangrove and Redskin Coral Reef after the December 26, 2004 Indian Ocean tsunami Chemical index of alteration (CIA): The mobility of elements of calcium, sodium, potassium and aluminum is investigated in detail using the Mobility Index (Chemical Index of Alteration). CIA is the molar Al2O3/(Al2O3+CaO+Na2O+K2O), where CaO refers to Ca that is not contained in carbonate and phosphate (Nesbitt and Young, 1982; McLennan, 1993). CIA has proven useful in evaluating the degree of weathering experienced by igneous rocks. Weathering of silicates, in particular, feldspar is accompanied by leaching of the more soluble elements (e.g., Na, K and Ca) and retention of elements that reside in clay minerals (e.g., Al). The CIA of unweathered igneous rocks is generally low (<50) and it increases with the degree of weathering (Nesbitt and Young, 1982); shales have CIA between 60 and 80 (Teng et al., 2004). When evaluating chemical changes associated with weathering, a number of workers normalize absolute concentrations of �mobile� elements such as lithium, to that of a presumed immobile element (e.g., Al, Ti, Zr and Nb), in order to evaluate the relative depletion or enrichment of the mobile element. Chemical Index of alteration as a function of depth in South Andaman In general, the CIA shows an overall in increase with depth for the study sites, although it is expected that the weathering is predominant in the surface sediments. However, it can be observed that the CIA is greatest at 6 to 8 cm depth in all the study sites, which further strengthens the assumption that the sediments above this layer has been newly deposited. Sediment samples below 12cm depth in all the study sites are highly weathered (CIA = 81-87), with the exception of Redskin coral reef site (64-78). This suggests that all the sediments (upto a depth of 48cm) have been newly deposited by the tsunami. High salt content in the soil surface was due to the persistence of tsunami-derived seawater. The recent FAO survey has found that residual high content of salt is in the layers of clay and silt left behind by the tsunami waves. The clay/silt layer can be identified easily by cracks that spread across the surface of the soil. In many areas, trenching or digging down to a depth of just 20 cm reveal a fine grey layer. The geochemical heterogeneities were found in sediments collected from sections containing a conspicuous tsunamigenic layer match the observed lithological and textural variations. As observed by us in this study, tsunami sands have higher SiO2, CaO and Sr concentrations, which is indicative of an increasing siliceous-sand component together with variable limestone and marine shell admixtures. The SiO2, CaO and Sr enrichment is related to minor fine sand and carbonate bioclast enrichment within a thin horizon which is correlative with the tsunamigenic sand deposit in adjacent areas. On top of this level sedimentation resumed to silt and clay and displays a significant positive anomaly for MgO and Cl, suggesting deposition on seawater dominated environment. Average Chemical index of alteration (CIA) for the surface and bottom sediments in Tsunami affected sites of South Andaman Location CIA Surface Bottom Sippighat-Agriculture-soil 81 78 Sippighat-Mangrove-sediment 81 83 Wright Myo Mangrove 84 86 Redskin-Coral Reef 68 73 Distribution of trace metals and organic carbon: The geochemical heterogeneities found in sediments collected from locations of South Andaman, containing a conspicuous tsunamigenic layer match the observed variations. Indeed, the estuarine mud displays similar and relatively lower SiO2/A12O3 and CaO/Al2O3 ratios, being enriched in several minor and trace elements (Cu, Cr, Ni, Zn), which are easily incorporated by the clay fraction. Tsunami sands have higher SiO2, CaO and Sr concentrations and ratio that are indicative of an increasing siliceous-sand component together with variable limestone and marine shell admixtures. The SiO2, CaO and Sr enrichment is related to minor find sand and carbonate bioclast enrichment within a thin horizon which is correlative with the tsunamigenic sand deposit in adjacent agricultural areas. Sharp differences in pH have been observed particularly at Sippighat (Agricultural land), between the agricultural and mangrove sites. The sediments cored in the Wright Myo mangrove and in the Redskin Coral reef sites are quite monotonous with reference to pH. There is surface disturbance in organic matter content, with the exception of Wright Myo, where there is a consistent enrichment with depth. At Redskin Island, surface enrichment of organic carbon is obvious, possibly due to re-suspension bringing the organically rich-sediment to the surface. Vertical profile of Cu in the core sediments from South Vertical profile of Cr in the core sediments from South Andaman Vertical profile of Zn in the core sediments from South Andaman Vertical profile of Ni and Zn in the core sediments from South Andaman The results of our geochemical investigation of sediments from South Andaman suggest that this region and the adjacent land area are highly impacted by the December 26, 2004 Indian Ocean tsunami. Salinity levels were considerably higher in the creeks and backwaters than average marine conditions. Our geochemical data suggests that there is deposition and reworking of sediments at least in the top 15cm in the Sippighat (agricultural and mangrove areas) and > 30cm in the Redskin Island Coral reef area. However, the geochemical record is very even in the Wright Myo mangrove creek, suggesting no strong sedimentological impact of the tsunami wave. Variation of pH with depth in sediment cores collected from South Andaman [left: Sippighat (Agriculture and mangrove site) center: Wright Myo, right: Redskin Island Coral reef site] Organic carbon and organic matter content in the sediment cores of South Andaman In summary tidal studies carried at Wright Myo, South Andaman showed that there is a rise in local mean sea level of an order of 1.00 m due to subsidence at South Andaman as ascertained from GPS and actual field measurements. Comparison of pre- and post tsunami water quality from South and North Andaman clearly show increases in ammonium concentration probably due to constant inundation and submergence. Dissolved trace gas fluxes show a marginal decrease from pre- to post tsunami conditions also due to the influence of seawater inundation. Sulfate and salinity inhibit CH4 formation and emission under these conditions to a large extent. Further, sediment chemistry indicates enhanced occurrence of major and trace elements both in the mangrove and coral reef areas and in the adjacent agricultural landscape. Photographs of ecological damage due to the Indian ocean Tsunami Top Left: Mangrove area in Sippighat, South Andaman destroyed due to continuous inundation of seawater due to subduction of land Top Right: Seawater intrusion in agricultural fields adjacent to mangrove area in Sippighat, South Andaman, due to subduction of land Bottom Left: Mangrove area in Kalighat Creek, North Andaman exposed even during spring tides due to emergence of land Bottom Right: Coral reefs ecosystem of the North Reef, North Andaman, exposed during spring tide due to land emergence 4.1.3. Assessment of environmental degradation due to desertification of land Desertification is the degradation of land in arid, semi-arid and dry sub-humid areas caused primarily by human activities and climatic variations. Desertification does not refer to the expansion of existing deserts. It occurs because of dry land ecosystems, which cover over one third of the world�s land area, are extremely vulnerable to over exploitation and inappropriate land use. Poverty, political instability, deforestation, overgrazing and bad irrigation practices can all undermine the land�s fertility. Over 250 million people are directly affected by desertification. In addition, some one billion people in over one hundred countries are at risk. These people include many of the world�s poorest, most marginalized, and politically weak citizens. (Source: The United Nations Convention to Combat Desertification: An Explanatory Leaflet). The scientific facts and knowledge on the causes for the depletion will aid in preventing the depletion or deterioration of the resources and this study was undertaken by CPEES with the objective of identifying areas that are subjected to desertification using satellite data. This study was jointly carried out by Space Application Centre, Ahmedabad and Institute of Remote Sensing, Anna University. Initially the Theni district in Tamil Nadu was taken up for analysis and the mapping of Theni district was carried out using ENVI and ERDAS Image and processing softwares purchased under the programme. Before commencing the classification, the satellite image was Georeferenced using GPS. After Georeferencing, the classification was carried out and identified the areas that are degraded due to desertification. The vegetation degradation mapping was carried out considering two main indicators (viz) I) decrease of forage productivity and ii) decrease of the percentage of vegetation. The decrease of forage productivity image and the decrease on vegetation cover percent image were combined by overlay analysis and the vegetation degradation image was created. The identification of area subjected to desertification has been extended to entire state of Tamil Nadu and the map prepared for this states is shown in the Figure above. The severity of degradation has been assessed as slight, moderate and severe and is presented in the above figure. The above study is being continued with microwave data to derive indicators of land degradation to be synergized with optical data. The efforts to use the hyper spectral data for the same purpose are on avail for which the fieldspec and CROP SCAN spectro radiometer were used and consequently a method is being evolved for estimating suitable indices for identifying the land degradation process. This will indicate the status of desertification and its severity level, which in turn will help the planners to suggest suitable remedial measures to prevent further desertification and convert the land into productivity one. The major output of this study is a map showing desertification status and the type and cause of it. The type such as wind eroded soil, water eroded stretch would indirectly indicate the problems in socioeconomic and agricultural practices. The type of land degradation and the intensity of it would combinedly help in identifying the primary causative factors such as agriculture practice, intensity, calendar with respect to the climatic variables and the need for suitable change. The information on desertification status would also throw light on the future threat to the land if left unattended. For example a small stretch in Theni district was found severely affected by wind erosion. Local people have gone in for cashew nut plantation in the small sand dunes formed. Some local fencing methods have also been introduced. A lot of Agricultural stretches adjacent to the foot hills of Westen Gharts range in this region has water eroded soil overlay, indicating a need for more number of water recharging structures in the foothill regions. In fact, farmers have started fruit plantation in these region to make use of the descending water during rainfall spells. The users of such powerful tools developed will be the planning authorities on land development and the farmers and landowner would be the stakeholders.