Coringa Mangrove of Andhra Pradesh in the East Coast of India (Fig
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1 DEVELOPMENT TEAM Project organisation : ICMAM Project Directorate and Institute for Ocean Management, Anna University Primary, secondary data collection : Prof. A. V. Raman and team Marine Biological Laboratory Andhra University Database design and development : Dr. S. Sundaramoorthy Dr. T. Shunmugaraj and Mr. V. Ramanathan of ICMAM-PD Dr. V. Ravi Dr. S. Rajaguru and Mr. K. Sivakumar of IOM, Anna University Remote sensing and GIS : Mr. V. Balamurugan and Dr. S. Sundaramoorthy of ICMAM-PD Development of information system : Dr. S. Sundaramoorthy and Mr. V. Balamurugan of ICMAM-PD Multimedia design and development : Ms. K. Radha and Dr. S. Sundaramoorthy of ICMAM-PD Project review : Dr. B. R. Subramanian and Dr. V. Sampath of ICMAM-PD 2 1. I ntroduction Mangroves are one of the most productive ecosystems on earth, deriving nourishment from terrestrial and tidal waters. Mangroves serve as important feeding, nursery and breeding grounds for a variety of commercially important organisms and also serve as protected areas for endangered species. Mangroves act as a barrier against cyclones, thus protecting the human settlement and other properties. They stabilize coastal sediments, thus preventing coastal erosion. However, worldover, mangroves are facing degradation, owing to the intertidal areas being extensively developed for aquaculture or other purposes. Loss of mangroves is a cause of serious environmental and economic concern. Therefore, mangrove habitats need to be protected. In India, mangroves are distributed at selected locations along the east and west coasts in the mainland and in the islands of Andaman and Nicobar. In the mainland, the mangroves are relatively well developed in the east coast than in the west coast. In order to assess the status and suggest suitable management plan for protection of mangroves, coral reefs, etc., the Department of Ocean Development (DOD) has initiated an activity namely, “Development of a Critical Habitat Information System (CHIS)” using modern tools like GIS, RDBMS, remote sensing, etc. DOD has established an Integrated Coastal and Marine Area Management Project Directorate at the National Institute of Ocean Technology (NIOT) campus in Chennai to implement this programme. Critical Habitat Information System has been developed for 11 critical habitats along Indian coast, one of which is Coringa mangrove of Andhra Pradesh in the east coast of India (Fig. 1). The major objective of this study is to develop an Information system on Coringa mangrove using GIS, incorporating components of remote sensing and an external database. This would help in assessing the status of the habitat, in suggesting suitable management action plan for protection and long term monitoring of the Coringa mangroves. Fig. 1 - Location of Coringa mangroves 3 2. Coringa – General Description Coringa mangrove (Lat. 1644’ to 16 53’ N and Long. 82 14’ to 82 22’ E) is situated south of Kakinada Bay and is about 150 km south of Visakhapatnam. Coringa is named after the river Corangi. Coringa mangroves receive freshwater from Coringa and Gaderu rivers, distributories of Gautami Godavari river and neritic waters from Kakinada bay. Numerous creeks and canals traverse this ecosystem (Fig. 2). Kakinada Bay Coringa mangroves Bay of Bengal Gautami Godavari river Fig. 2 - An imagery of Coringa mangroves 2.1 Coringa Wild Life Sanctuary In order to rehabilitate the salt water crocodile which was at the verge of extinction and to protect the other endangered species, such as Olive Ridley turtles and Indian Otter, the Government of Andhra Pradesh declared a part of Godavari mangrove system as Coringa Wild Life Sanctuary in July, 1978. The Coringa Wildlife Sanctuary covers an area of about 208 sq.km. It is located between Lat. 1630’ and 17 00’ N and Long. 82 14’ and 82 23’ E in the East Godavari District. About 120 species of resident and migratory birds (egrets, cormorants, etc) depend on this area for breeding and nesting. 4 3. Major Types of Habitat 3.1 Mangrove Coringa is the second largest mangrove formation in India, next to Sundarbans. The Coringa mangroves are bordered on the northern side by Kakinada Bay. The area of Coringa Reserve forest is 3156 hectares and of Coringa Extension forest is 9442 hectares including waterways. In Coringa, totally 15 species of mangroves were recorded. The dominant genera are Avicennia, Excoecaria, Aegiceras, Rhizophora and Sonneratia (Fig. 3). Fig. 3 - View of mangrove in Coringa 3.2 Turtle Nesting Ground Minor nesting of Olive Ridley turtle, an endangered species, was reported in the Andhra Pradesh coast (Whitaker and Kar, 1984). Silas et al. (1984) were of the opinion that while many of the turtles migrate to Orissa (Gahirmatha) coast, a few of them reached the Tamilnadu and Andhra Pradesh coast for nesting. Along the Andhra Pradesh coast, a 25 km stretch from Kakinada (Lat. 1657' N and Long. 82 12' E) to Konapakapeta was identified as nesting place of marine turtles. In Coringa region, the sand spit and the Hope island are important nesting grounds (Rao, 1985). The nesting season was reported to be during Oct- Feb. 4. Climate The distribution and health of mangrove plants are largely governed by climatic factors such as solar radiation, temperature, rainfall, wind, etc. During 1995-97, atmospheric temperature ranged from 24.8 to 32.6C. The annual rainfall was 871, 1627 and 1156 mm for the years 1995, 1996 and 1997, respectively. Annual mean wind speed ranged from 2.1 to 2.3m/sec. The observed high rainfall and temperature seem to be conducive for the health of mangroves in Coringa. 5 5. Development of I nformation System The Information System was developed in GIS by integrating the data collected from various sources, viz., (1) theme maps from conventional and remote sensing data, (2) data on water quality and biological parameters from field investigations, and (3) data on socio- economics, etc., from Govt. organisations. The Information System comprises the following: [ Spatial distribution of mangroves. [ Hydrographical features such as bathymetry, tides, currents. [ Qualitative and quantitative data on distribution of flora and fauna, viz., mangroves, phytoplankton, zooplankton and benthos. [ Causes for changes in mangrove environment. 6. Methodology Primary data comprise remote sensing data and data collected from field measurements on various parameters. Satellite data alongwith ground truth observations provided information on spatial features. Field data on water quality parameters were collected using standard methodologies. Data on biological parameters were collected for three seasons, using standard methodologies described in the Manual (ICMAM-PD, 1998). Sampling locations were fixed using GPS in the study area. These field data were stored in Oracle RDBMS as tables. GIS provided the capability to store both the spatial features and the attribute data from field investigations from RDBMS. 6.1 Remote Sensing Satellite data of 1988 (IRS 1A) and 1998 (IRS 1C) were analysed using ERDAS image processing software, alongwith ground check using GPS for geographic reference to prepare the landuse /landcover maps. The base maps were used to rectify the digital satellite data for positional accuracy. Landuse maps of 1988 and 1998 were analysed to detect the changes using overlay facility of GIS. 6.2 Geographic I nformation System GIS is a powerful tool to store, manipulate, analyse and retrive spatial and attribute data. Using bases prepared from toposheets, maps on geology, geomorphology, soil, etc., were prepared from the data provided by Govt. departments and stored as themes in ArcView. Attribute data of environmental parameters from RDBMS were attached to respective themes in GIS. 6 6.3 Database Oracle, a powerful Relational Data Base Management System (RDBMS), was used to store various attribute data collected from field investigations. Field data on water quality, substratum and living organisms during the period 1998-99 were collected. Socio-economic data were also collected. All the attribute data were stored in Oracle as tables. 6.4 Field Data Collection Data on water quality and biological parameters were collected during June-July 1998 (southwest monsoon), December 1998 (post-monsoon) and May-June 1999 (pre-monsoon) at selected locations in the Bay-Estuary complex of Coringa mangroves. Data were collected at 24 stations, one in the open sea, 9 in Kakinada Bay, and 14 in Coringa-Gaderu mangrove environment. For convenience, 10 stations in Bay were grouped into North Bay (6 stations) and South Bay (4) and 14 stations in mangrove environment were grouped into Coringa (3) and Gaderu (11). In addition, 17 more locations were selected to study mangrove species composition and density (Fig. 4). Aquatic T Mangroves *i Fig. 4 - Sampling locations in the study area 7 7. Physical Environment 7.1 Geomorphology Coringa does not show any major topographical feature, with the exception of the Kakinada coast, which is largely a low-lying area. The lower part of the delta is made of a series of sand ridges interpreted to be ancient beach ridge forms, due to high waves and detrital material brought by the river from its drainage basin. Fractures have controlled the drainage and truncated some of the river courses. Geomorphology of this area is classified as mudflat, mangrove swamp, sandy beach and sandy island (Fig. 5). Mudflat Mangrove Sandy beach Oxbow lak e Point bar Sand spit I sland Flood plain Plain land Upland Fig. 5 - Geomorphology of Coringa region 7.2 Soil The deltaic region mostly contains black cotton soil with deep extensions in subsurfaces. They are moderately drained. The texture of the soil is ‘silty clay’ with 50-65% of clay. The dominant clay mineral is smectite. These soils are low in organic carbon, which ranges from 0.3-0.5% indicating rapid mineralisation. 8 7.3 Topography The Coringa mangroves are bordered on the northern side by Kakinada Bay. On the western side is the mainland, formed of deltaic and flood plains. The coastal strip north of Kakinada consists of wind blown sand and sand dunes which are succeeded landward by laterites, sandstones and khondalites.