Analysis of the hydrodynamic data for the offshore zone along Chavara coast, as part of a program on heavy mineral budgeting funded by Indian Rare Earths Ltd. (IREL), showed a redominance of southerly flows at the offshore field sites suggesting southerly movement of sediment on the inner shelf. Interestingly, this net movement could counter-balance the strong net northerly transport identified in the modeling of littoral drift and thereby explains how the sedimentary balance could remain stable, even in the presence of strong net transport vectors. The cross-shore flows are decided by the wind. Notably, the offshore flow would be expected to induce an offshore sediment flux, although other processes such as wave asymmetry, intra-wave suspension phase lags or coupling of current and wave activity may partly counter-balance this effect. The onshore flows would be expected to lead to beach accretion. It is seen that the timing of onshorecurrents coincides with periods of beach accretion measured by beach profiles.

Sedimentological studies indicate that sediment is regularly mobile on the beach and on the inner shelf, out to 8 m depth. The capacity of waves and currents to move sand across and along the shelf has been clearly demonstrated. In addition, the results show that the heavy and light sand move differently,such that the light mineral is winnowed out of the beach sediments during periods of erosion and arrives first during the early stages of an accretion event. This is confirmed withthe video observations and the measurement of heavy sands in the beach sediments.

The longshore transport model predicted a net northward flux of 125,000 m3/yr along the section of coast, north of Vellanathuruthu mining site and 209,000 m3/yr in the south. The computed cross-shore fluxes are of the same order of magnitude as the measured beach volume changes.Interim total annual extraction volumes were recommended and a monthly distribution of mining volumes were provided. The total volume recommended is equal to the annual input during the accreting phase.The Integrated Coastal Zone Management Plan (ICZMP) has also been proposed for the Panchayats bordering the Neendkara-Kayamkulam coast and is mainly based on issues pertinent to coastal regions and takes into account of the hazards due to erosion, unhealthy settlement practices of the coastal region, availability of space, mineability of heavy minerals and health of the ecosystems.

PANEL DISCUSSION ON NATURAL BUILDING MATERIALS

A panel discussion on natural building materials was organized by CESS on 3rd May, 2002. The meeting was attended by various stakeholders representing building materials.The panel made the following specific recommendations.

River Sand

Detailed assessments are to be made for all the major river basins of Kerala to regularize the sand extraction based on existing sand reserve, natural replenishment and environmental problems. This should be done without any delay. Conduct environment impact assessment of sand mining projects.

Alternative building technologies with low sand/no sand content to be developed.

Regulate building construction through appropriate legislative measures.

Create awareness among people on the finite character of river sand at different levels.

Enforce the ban on beach sand mining using provisions of CRZ Notification.

Adhere to the provisions of Sand Mining Act.

Immediate steps to be taken to intensify research activities leading to the finding of suitable, low cost and easily available alternatives to river sand.

Use of sea sand as an alternative to river sand has to be initiated with scientific studies.

Develop technologies/opportunities for offshore sand mining.

Encourage use of crushed rock (‘manufactured sand’) as an alternative to river sand with scientific studies and appropriate codes suggested.

Continued funding for R&D activities may be ensured for updating the database, technologies and management.

Alternatives to river sand to be developed urgently (e.g. palaeo-rivers, palaeo-beaches, palaeo-channels).

Part of the revenue collected from sand mining should be used for protecting the river environment, supporting R&D activities and developing alternatives.

Encourage liberal import of building grade sand.

Mechanisms to rehabilitate the affected labourers.

Clay

Prepare a database on the availability of different clay types and their physico-chemical and geotechnical properties for brick and tile manufacturing.

Identify alternative sites excluding paddy fields for excavating clay, viz. silted clay in ponds/reservoirs/river bunds/ backwaters etc.

Conduct environment impact assessment of clay mining projects.

Substitute with locally available lateritic clay.

Regulate clay mining through legislation for conservation.

Popularise building technology using mud.

Rehabilitation of mines.

Hard Rock

Update the database on hard rock availability and their physico-chemical and geotechnical properties.

Carryout detailed resource assessment of various hard rocks being used/can be used for construction.

Detailed physico-chemical and engineering properties of various rock types are to be studied for its use in the building sector.

Identify suitable rocks for use as rock sand (substitute to river sand) and develop technologies for this.

Evolve mechanisms for the rehabilitation of river sand mining labourers in the rock sand sector.

Laterite

Kerala is the land of laterite. More than 60% of the State is covered by laterites/lateritic material. All scientific studies on laterites indicate that there is no baseline data on this natural resource viz. areal distribution, volume, physical, chemical, geotechnical and hydro geological properties, which help, in optimal utilization of this natural resource for sustainable development. Among the objectives of the study include the understanding of various physical properties of laterites, its distribution, thickness of laterite, volume of laterite resources, hydro geological conditions in lateritic terrain and to suggest water conservation methods.

The results obtained indicate that the laterites in Thiruvananthapuram district are of different ages i.e. Pre-tertiary & Post-tertiary periods and have varied physical and chemical properties. Thickness varies from 2m to 35 m. Porosity values are higher in laterites over tertiary formation suggesting it to be ideal sites for water conservation besides forming a natural reservoir.

Detailed resource assessment of various laterites for quarrying has to be carried out, including the present day quarries with aerial extent, volume and the environmental impact of mining.

Devise methods to use laterite waste to obtain stabilized bricks.

Fast curing techniques are to be developed to meet the increased demand and also for cost effectiveness.

Technological interventions and value addition in laterite as building material.

A Synthetic Aperture Radar (SAR) interferometry (in SAR) technique was experimented in Shuttle Radar Topographic Mission (SRTM) conducted by NASA, USA in collaboration with Germany and Italy. SRTM was an eleven day mission, which, was launched on 11th February 2000 at 23:13hrs IST by the Space Shuttle Endeavor. SRTM passed through Idukki region. Four test sites were selected in the region at Kurissumala, Vagamon and Vedikuzhi and experiments were carried out by installing Corner Reflectors (CRs) during the SRTM pass. CRs were installed based on the azimuth and elevation of the Space Shuttle at the time of pass. The ascending pass of the Space Shuttle Endeavor occurred over the Idukki test site was on 15th February 2000 at 10:23:57 hrs IST (3rd day after launch) and the descending pass was on 16th February 2000 at 21:13:27 hrs IST (4th day after launch). Corner Reflectors (CRs) were installed at four pre-determined sites in the test area around Vagamon, Kurissumala, and two sites near Vedikuzhi. The acquired microwave In SAR data through SRTM of the test sites at Idukki area will be used to generate DEM and to validate the DEM derived from SRTM data for Terrain Dependent Accuracy. The DEM of the Idukki test site will be made available from DLR, Germany through NRDMS, DST, Government of India.

The Idukki wildlife sanctuary forms the catchment of one of Kerala State’s most vital reservoir-cum-dam systems,the Idukki hydroelectric project, the biggest of its kind in Kerala State. This reservoir impounds water of the Periyar river, the longest river in Kerala, by three dams at Idukki (a concrete arch dam), Cheruthony and Kulamavu (gravity type concrete dams). The power requirement of Kerala is very much dependent on Idukki project. Any anthropological activity that leads to the depletion in the capacity of the reservoir and consequent loss in energy budget will affect the entire power grid of the State. Even though a large siltation bed to contain the incoming silt load was provided during the commissioning of the dams, soil erosion, at an alarming scale, was reported from the catchments, which will adversely affect the reservoir capacity. Disturbances due to human activity such as cultivation and felling of forest trees have aggravated the problem of soil erosion in the Idukki Wildlife Sanctuary. Soil manipulations in the plantations of cardamom, coffee, tea and eucalyptus in areas adjoining the reservoir has further accelerated the problem of erosion and siltation of the reservoir. Since erosion cannot be prevented, some sedimentation of the reservoir could be expected. However, treatment of the catchments is vital to reduce the rate of sedimentation to a minimum, thereby prolonging the life of the reservoir. It must also be noticed that every part of the catchment does not yield equal amount of sediments per unit area. The sediment yield depends on many factors such as rainfall intensity, erodability of soil, slope, land use, vegetation cover, drainage density, agricultural and soil conservation practices or lack of them. Hence, a system of priority determination for catchment treatment based on terrain evaluation, application of USLE along with field measurements were attempted and soil conservation measures in priority areas were proposed to check more sediments in the Idukki Wildlife Sanctuary. The objectives of the project include terrain analysis, determination of physico-chemical characteristics of soil, delineation of erosion prone areas, quantification of soil loss, monitoring of sediment yield from a critical area and suggestion of erosion management strategies for the sanctuary .

Characterisation of soils within the closed evergreen forests of Kerala

This project is sponsored by the Department of Forests & Wildlife, Government of Kerala, sanctioned under the specialscheme “Conservation and Development of hill shola forests” of the 10th Finance Commission, Govt. of India Sholas are unique forests, which exist at altitudes of 1500m above the MSL in the Western Ghats whose trees are stunted in nature. Twenty-one soil profiles, representing twelve sholas and adjoining vegetations distributed in the districts of Idukki and Wynad, were studied in detail in order to have a deeper insight into the physico-chemical characteristics and soil fertility status. The type of vegetation was found to affect the physico-chemical properties and the fertility status of the soils studied. Besides textural analysis, five important physical parameters studied were, the single value constants, namely, the bulk density, particle density, maximum water holding capacity, porosity and volume expansion. No general trend could be noticed for physical parameters between profiles of sholas and adjoining vegetations though the values recorded were relatively higher for sholas and evergreen forests compared to other vegetation types in most of the horizons. The distribution of clay within the profile was fairly uniform in the case of sholas and evergreen forests compared to grasslands and monoculture plantations. In the case of L/A, ratio surface horizons of shola forests and grasslands invariably recorded higher values compared to the lower horizons. Values of water holding capacity, porosity and volume expansion were found to be more or less uniform through out the profiles for both sholas and grasslands. Soils of the sholas were found to be less acidic with a higher base status and cation exchange capacity. They were rich in organic matter with a relatively higher content of available N, P, K, Ca, Mg and micronutrients. Distinct variations were observed in the physico-chemical properties of shola soils of Idukki and Wynad districts. Soil samples collected from sholas of Wynad district were found to contain higher amounts of organic matter and plant available nutrients compared to soils of Idukki sholas. Some of the profiles exposed in Idukki sholas were characterized by pedons similar to podsols of temperate regions. These profiles were having a thick and bleached epipedon with a very thick lower alluvial horizon formed by the deposition of organic fractions and mineral matter.