Annals of R.S.C.B., ISSN:1583-6258, Vol. 25, Issue 6, 2021, Pages. 12922 - 12929 Received 25 April 2021; Accepted 08 May 2021.

Effect of 2018 Flood on Land use changes of Achankovil River Basin, , South West Coast of

1* 2 2 3 Parvathy Mohan ,Johnson Baby ,G Prasad ,Karthik M 1*.Zoology Research Centre, St.Stephen’s College, , University of Kerala, India. 2.Associate Professor and Principal, Department of Zoology, Christian College, Chengannur, Kerala,India. 2.Professor and Head, Department of Zoology, University of Kerala. 3.Dept. of Geology, Banaras Hindu University, Uttar Pradesh, India

Abstract The paper discusses the change in land use of Achankovil river basin of Kerala before and after the flood in 2018. A base map of the basin boundary and main stream course is created with the help of GIS (Arc GIS 9.1) from toposheet 1:50000 scale from which the land use map is digitized keeping the scale. Imagery data from google earth is used for updating land use map which is used for field work. Field level information of the basin is input into the land use map and updated with the help of GIS. GPS reading of all the sampling locations is integrated with the land use map to understand the distribution of land use categories and its possible influence on the sampling parameters. Land use map was prepared in April 2018 and repeated in September 2018 in view of the unexpected flood in the state during August 2018. Eight stations such as Achankovil, Konni, Omalloor, Konathumoola, Kaippuzha, Attuva, and covering upstream, midstream and downstream are selected for assessing the impact of flood on land use. From the comparison of land use maps before and after flood, it is clear that the flood has damaged a total of 28.15% land use of Achankovil basin fully or partially. Among the total loss, mixed crops faced the highest damage of 61.81% ,14.79% loss to paddy field, 14.76% of fallow land and 5.92% settlement with mixed tree crops were damaged.

Key words: Land use, Physiography, Flood, GIS, Achankovil river basin.

Introduction

Increased rate of urbanization along with other anthropogenic interventions pose major challenges in river basins, which may ultimately affect the basin ecology and end up in serious natural havoc like floods and droughts. Land use is regarded as the preparations, actions and responses by people to produce, alter or maintain a specific land cover type (FAO, 1997). Land cover is the observed cover on the earth's surface (Di Gregorio & Jansen, 1998). By considering the river basin, the hydrological realm of the basin gets affected by the spatio-temporal changes in land use. Turning of waterlogged wetlands into built-up areas and deforestation directly affect the nature of the basin and natural water flow regimes, where the ultimate consequence is flood (Mayaja & Srinivasa, 2017). Among natural resources, land is one among the important as numerous developmental activities and life depends on it (George et al., 2016).Analyzing the spatial and temporal variations in land use and land cover of a river basin provides meaningful insight to these issues. The wide ranging changes in the socioeconomic arenas of Kerala state during the last decade has speed up the rate of built up area generation and subsequent landscape changes. Analysis of the spatio- temporal deviations in land use and land cover (LULC) of a river basin would offer scientific perceptions to these changes.

Flood is the most common type of natural hazard due to its devastating effects in the affected area. The state of Kerala in 2018 experienced one such flood with devastating impact on river basins including Achankovil river. Achankovil River located between 760 24’ to 770 18’ E longitude and 90 2’ to 9019’ N latitude is different from near by rivers in basin shape and channel geometry (Dhanya, 2014). It is one river in Kerala on which thousands of people depend for their fresh water requirement. Besides the shrine, ‘Achan kovil’- meaning father temple, situated in the reserved forest near the origin of this river is being visited by thousands of devotees every year as part of pilgrimage, one of the largest pilgrimages in India. The river flows 128km through the districts of , and with a total basin area of 1361.92sqkm.The course of the river is not steady and they progress through numerous structural blocks of copious dimensions (Dhanya, 2014). The rainfall in Achankovil basin on the other hand is distributed fairly uniformly throughout the basin and an average of 2800.10mm rainfall for the last ten

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years has been reported in the catchment area (Radhamany, 2019). Flash flood is normally from heavy monsoonal outburst and large concentration of run-off which exceeds river systems (Petry, 2003). The structural specialty together with increasing anthropogenic pressure from land use change, pilgrimage and urbanization can cause contamination of the freshwater resource. Nature of the river and survival of inhabitants in its basin depends on the varied land use categories. The aquatic ecosystem continuance and affluence of the biodiversity in a basin is under the impacts that are molded by land use (Vinod et al., 2013).

In the state of Kerala various studies pertaining to land use changes in river basins are conducted. Since the rivers of the densely populated state are very small and act as the major sources of drinking water, the spatio-temporal changes in land use that have direct control on its hydrological realm are crucial (Letha et al., 2011). Increased rate of urbanization as major challenges faced by river basins, ultimately change the basin ecology which end up in serious natural havoc like floods and droughts. Influence of land uses on the water quality has also been a matter of concern in rivers of the state. Loss of vegetation and wetland agriculture has been a major concern due to spatial and temporal changes in LULC as reported from the basin of Bharathapuzha, the longest river in Kerala (Suresh & Bindu, 2015).

Flood hazard is imminent in basins where depletion in wetland use occurs due to uncontrolled urbanization. Flood hazard risk zone mapping has to be done to devise mitigation and management options. Such maps are prepared for basin in Kerala using using ArcGIS and ERDAS Imagine tools (Nair et al., 2015). The thematic maps prepared for rainfall distribution, drainage density, land use, soil type, size of micro watershed, slope, etc., are given respective ranks and weights and based on them the hazard map delineating hazard affected area as very low, low, moderate, high and very high-risk zones are generated. Similarly, in 2013, flood hazard prone areas in Achankovil river basin were also prepared by Weighted Overlay Techniques in ArcGIS (Ajin et al., 2013). Though the study clearly identified the flood hazard prone areas of the basin, enough follow up activities has not been made to safeguard the possible damages from flood.

Under this perspective, change in land use of Achankovil occurred during the flood 2018 has to be evaluated as a precautionary measure to safeguard the drinking water resource, livelihood of the local people and management of a possible flood in future. The study is an attempt to evaluate the effect of flood on the land use of Achankovil basin before and after the devastating flood of Kerala in August 2018. Material and methods

Physiographically the river basin can be divided in three major classes such as high land, midland and lowland. Eight locations for observing the land use of the basin and the impact of flood on land use are selected representatively from these classes. Sample locations 1 (Achankovil) and 2 (Konni) are located at the upstream highland area, locations 3(Omalloor), 4 (Konathummoola), 5 (Kaipuzha) and 6 (Attuva) are located in the midland region and locations 7 (Pallippad) and 8 (Veeyapuram) are located in the low land downstream area. Latitude and longitude of each station is depicted in Table 1. Table 1. Details of locations of the study Station No. Location Name Latitude Longitude 1 Achankovil 9.06 763N 77.09 215E 2 Konni 9.14 56N 76.50 15E 3 Omalloor 9.14 07N 76.45 11E 4 Konathumoola 9.13 39N 76.41 53E 5 Kaippuzha 9.13 54N 76.40 18E 6 Attuva 9.14 36N 76.37 56E 7 Pallippad 9.15 48N 76.30 14E 8 Veeyapuram 9.19 29N 76.27 54E

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Annals of R.S.C.B., ISSN:1583-6258, Vol. 25, Issue 6, 2021, Pages. 12922 - 12929 Received 25 April 2021; Accepted 08 May 2021.

A base map (boundary and main stream course) is created with the help of GIS (Arc GIS 9.1) from toposheet 1:50000 scale Nos. 58 C/7, 58 C/11, 58 C/12, 58 C/15, 58 C/16 and 58 G/4. Land use map is digitized from the toposheet of the same scale. Imagery data from google earth is used for updating land use. The land use map thus created is used for the field work to get the exact distribution of land use pattern in the field. Field level information of the basin is input into the land use map and updated with the help of GIS. GPS reading of all the sampling locations is integrated with the land use map to understand the distribution of land use categories and its possible influence on the sampling parameters. Land use map was prepared in April 2018 and repeated in September 2018 in view of the unexpected flood in the state during August 2018.

Results and Discussion Land use of Achankovil river basin before flood

Achankovil river basin has an area of about 1361.92 Sq.km. Sample locations of Achankovil and Konni were located in the highland area. Forest, Teak, forest plantation (teak and bamboo) and rubber were the major land use categories in location 1. The major land use categories observed in location 2 were rubber plantation, mixed crop, settlement with mixed tree crop and patches of paddy. Midstream portion comprise locations 3 to 6. The major land uses in Omalloor (Location 3) were settlement with mixed tree crop followed by rubber and patches of paddy. Major land uses in Konathumoola, location 4 were mixed crop followed by settlement with mixed tree crop and patches of paddy whereas location 5 has mixed crop as the major land use followed by settlement with mixed tree crop and patches of paddy and rubber. Location 6 has mixed crop followed by fallow land and patches of paddy. Pallippad (Location 7) showed fallow land as the major land use category followed by mixed crop and paddy while Veeyapuram, location 8 was mostly occupied by fallow land and paddy (Fig. 1).

Figure 1. Land use of Achankovil river basin before flood

The land use categories of Achankovil comprised mixed crops, forest, teak, rubber, paddy, settlement with mixed tree crop, fallow land, river, water body, forest plantation, tea, land with or without scrub, settlement

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area and beach. The land use categories such as mixed crop, forest, teak and rubber constituted about 76.31% of the total area. The mixed crops including coconut, tapioca, banana, rubber, teak etc. dispersed all over the basin comprised the major land use category with 34.22% area. The forest area occupied 28.5% of the total area of the basin which included dense forest, open forest, small patches of teak plantation, teak and bamboo. The settlements were dispersed in all the land use categories. Teak plantation was found exceptionally high at upstream top area of the basin around and after the place, Achankovil which constituted 9.16%. Rubber plantation is of 8.32% of total basin which was distributed in the midstream and upstream locations while low lying area hardly had any rubber plantation. The settlements are dispersed in all types of land uses (Fig.1).

The existing paddy field constituted 5.52% of the total area of the basin. As per toposheet in 1980’s roughly 15 to 20% of the basin was occupied by paddy field. The extensive reclamation of wetlands seemed to have largely reduced the water holding as well as recharge capacity of the basin.Paddy reclamation was mainly affected by banana, tapioca, coconut and other mixed crops. Some of the locations were occupied by rubber. As per local residents, drought was very intense in summer months in the midland lateritic area even near the river. The valleys within the lateritic area were mainly occupied by paddy field in 1980’s. As the laterites can hold and recharge water for a longer time, recharge from the paddy fields and water bodies through capillary rise was the major source of groundwater in this region. Most of the small water bodies termed ‘Thalakulam’ and ‘Valkulam’ in the local vernacular, at the start of a paddy field have been reclaimed fully or partially at many regions.

The major land use change from 1980 in the highland was the conversion of forest into forest plantation and rubber. In the midland region, conversion of coconut and mixed crops to rubber was the major change. As the midland area was occupied by narrow valleys, most of the paddy fields were dispersed in the low land. As the low land was water logged and flooded during most of the times, the settlement density was high in the midland area. Impact of August 2018 flood on the land use of Achankovil river basin

Owing to the unexpected flash flood in August 2018, the land use of the basin had affected considerably. From the field observation and satellite imagery interpretation, it was obvious that the flood in 2018 was intense especially at the physiographically low land and valley floors near the river (Figs. 2 & 3). The local residents of each of the sampling location were consulted to refine the observations. It was found that extensive loss of mixed crops primarily banana and tapioca at the valley floor near the river had occurred during flood.

Table 2. Category wise loss of land use change due to flood in Achankovil river basin

Land use Category Area (Sq.km) Area (%) Mixed crop 236.99 61.81 Paddy 56.69 14.79 Fallow land 56.60 14.76 Settlement with mixed tree crop 22.71 5.92 Rubber 8.11 2.11 Settlement area 1.07 0.28 Land with or without scrub 0.72 0.19 Tea 0.31 0.08 Beach 0.20 0.05 Built up area 0.02 0.01 Total 383.41 100

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Figure 2.Land use damage caused by the flood in Achankovil river basin

Figure 3. Flash flood affected area of Achankovil river basin

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A comparison of land use before and after flood revealed that, a total of 28.15% land use of the basin was damaged fully or partially (Figs. 1 & 2). Among the total loss, mixed crops faced the highest damage (61.81%) accounting to 236.99Sq km area. 14.79% (56.69Sq km area) paddy field, 14.76% (56.60Sq km) fallow land and 5.92% (22.71Sq km) settlement with mixed tree crops was also fully damaged. Loss of land use at most of the locations was by and large in similar pattern (Table 2 & Fig. 2). Station wise impact of flood 2018 on land use

Achankovil: At Achankovil station, major land uses were forest, teak, forest plantation (teak), followed by rubber. There was evidence of high erosion and exposure of denudational hillocks at the southern flank of the location. The teak plantation occupied in the area affected the biodiversity and rain water recharge. Rubber plantation was seen even in the degraded forest area and the plantation crops and eroded denudational hilly complexes were observed to trigger surface run off. As a result, the river sand was seen almost washed off during the flood and concentration of pebbles and cobbles in the river occurred. Deep gully formation visible in the lateritic pockets at the northern side of the station was obviously due to the plantation practiced in the reserve forest area (Photograph 1). Konni: Settlement starts from Konni station and the major land use category surrounding the area was with rubber plantation followed by mixed crops. Surface run off was high and the river bank at many places were heavily eroded. The intense bank erosion affected almost 80% of the rubber plantation adjacent to the river. The mixed crops consisting patches of rubber were washed away especially in places like Kizhavalloor and Puthanveedil kadavu. Minor agricultural crops such as banana, tapioca and other tuber crops were totally destroyed in the valley floors (Photograph 2). Omalloor: The major land use pattern in Omalloor was mixed crops and settlement with mixed tree crops. Rubber with mixed crops was wide spread in this location. Near Arattubhagam kadavu, large stretch of banana plants was vanished due to flash flood. An open well was seen submerged and 500m length river bank was seen subsided. Konathumoola: Majority of the area surrounding Konathumoola location had settlement and mixed crops including patches of rubber plantation adjacent to the river bank. Lot of sand brought from upstream was seen deposited along the banks probably due to wide valley floor (Photograph 3). Bank erosion was negligible in the location possibly due to bamboo cultivation practiced in the area. Kaippuzha: Major land use in Kaippuzha location was mixed crops followed by settlement with mixed tree crops. Crops such as banana, tapioca and tuber crops were affected during flood. Few patches of rubber plantations were also found affected. The lateritic terrain in this region was told to experience drought in summer months. Attuva: Attuva have land use of mixed crops followed by fallow land. Few patches of rubber plantation concentrated in the reclaimed area were also seen. Bridge built across the river was found destroyed during the flood probably by hitting logs, rocks and materials from the upstream (Photograph 4). The area was visibly polluted with plastic dumps. Pallippad: At Pallippadmixed crops and fallow land were the main land use categories. Rubber plantation was very thin. The fallow land occupied paddy field, water bodies and wetland. Pollution by deposit of plastic bottles was also noted. Veeyapuram: The last location was Veeyapuram, the confluence area of Pampa and Achankovil rivers. The major land use category was fallow land followed by mixed crops. Plantation crops were not seen in this region. Reclamation was intense and impact of flood was visible on mixed crops.

The images taken form the sites clearly depict the effect of flood in some of the stations of Achankovil river basin shown in Photographs 1-4. As per the study delineating flood hazard prone areas in Achankovil River basin by Vinod et al. (2013), Veeyapuram fell in to very high hazard zone. Locations from Konni onwards were classified by these authors into high to very high hazard prone zones. The transformations in the land use pattern of Pampa river basin, a river basin adjacent to Achankovil, revealed 'strong negative changes', aggravating the havocs being experienced due to recurring flood and drought situations (Mayaja & Srinivasa, 2017). Basins of rivers like Bharathapuzha also suffers from land use change which found 31% depletion in the natural vegetation cover and 8.7% depletion in wetland agriculture area reflecting 32% increase in the urban spread (Raj & Azeez, 2010; Suresh & Bindu, 2015).

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Photographs depicting the effect of flood in Achankovil river basin

Photograph 1. Impact of flood at Achankovil station. Photograph 2. Bank collapse at Konni station due to flood.

Photograph 4. Bridge destroyed at Attuva station Photograph 3. Sand heap formed at Konathumoola station during food . during the flood .

Conclusions Reclamation of paddy field was the major problem faced by Achankovil river basin before the flood as the water holding capacity was reduced by cultivation of rubber and mixed crops. The riverine ecosystem was adversely affected by the flood and loss of land use categories occurred. Altogether, the flood has damaged 28.15% land use of the basin and among the total loss, mixed crops faced the highest damage accounting to 236.99Sq km area was lost followed by 56.69Sq km of paddy field, 56.60Sq km of fallow land and 22.71Sq km of settlement with mixed tree crops. Loss of land use occurred from upstream Achankovil to downstream Veeyapuram area. Proper protection of river bank by vegetation like bamboo is needed for the sustainability of the ecosystem as they support the river bank by preventing the landslide and bank erosion. Acknowledgement

We are thankful to the University of Kerala for providing financial support in the form of fellowship and to Mr. A. S. Pramodh Lal, Consultant Geologistfor his help during the preparation of land use maps.

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