- Kerala has already received 41 percent higher rainfall during the southwest monsoon. With uneven distribution of this excess rainfall some districts had very severe flooding of the kind seen only once in a century.
- By August 19, when the rain started subsiding, the rains and floods since June 1 had cost 370 lives in the state, displaced nearly 725,000 people into relief camps and caused damage to property that can truly be assessed only after the water recedes.
- Even though Kerala has faced vagaries of weather in the past, extreme weather events have become more intense and frequent in the recent years. And there could be more such events happening with greater intensity and frequency in the future.
- If this year’s flood was a shocker, the future can be more climate resilient if grassroots communities realise the adverse impact of tampering fragile ecologies and start working for their conservation.
As dusk turned to evening on Friday, August 10, the residents of Kerala and its diaspora spread across the world, watched the television with alarm as water released from the Cheruthoni dam of the Idukki dam and hydroelectric project rushed through the Periyar river valley to Aluva town. Extremely heavy rainfall in the upper catchment of the Periyar river catchment had forced the Kerala State Electricity Board (KSEB) to open the five shutters of the Cheruthoni dam, one by one, earlier in the day.
This was unprecedented in the history of the Idukki hydroelectric project, commissioned in 1976. The 138-metre-tall dam holds back the water of the Idukki reservoir, together with another arch dam on the northeastern side of the reservoir. With extremely high rainfall during the earlier days of the week, the water level in the reservoir had risen to 2401.68 feet from the mean sea level (MSL), dangerously close to the full reservoir level (FRL) of 2403 feet.
Kerala had received heavy rains in the preceding week. During the first 11 weeks of the southwest monsoon, starting June 1 to August 22, the state had an excess rainfall of 40.67 percent. Due to the rains and loss of lives and property it had caused, a state of red alert was announced in all of Kerala’s 14 districts.
By August 15, out of the total 39 dams in the state, 35 had opened their spillways to let out the water pressure built in their reservoirs. As rains lashed across the state, water was gushing through the rivers and streams leading to widespread flooding. In the hill areas the problem was compounded with landslides. By August 19 when the rain started subsiding, the rains and floods since June 1 had cost 370 lives in the state, had displaced nearly 725,000 people into relief camps and caused damage to property that can truly be assessed only after the waters recede.
A cascade of dams and reservoirs
Kerala is a state with a unique geography. A sliver of land hemmed in between the Western Ghats mountains and the Arabian Sea, the 570-km-long state is about 120 km at its broadest. Lengthwise, Kerala is divided into three distinct ecosystems – the highlands, midlands and coastal plains. The current excess rains had caused floods in multiple locations in all the three ecosystems.
With the Western Ghats blocking the rain-laden clouds of the southwest monsoon, 41 rivers that flow westwards take the precipitating water from the ridgeline to the sea. Since they descend at least 1,000 metres (and some of them above 2,000 m) in a few km, the rivers run rapidly down to the plains.
Cascade of dams and barrages over Periyar (purple), Chalakudy (blue) and Pampa (orange) rivers. Click on the pin for details. Map made with Google MyMaps by Kartik Chandramouli/Mongabay.
To trap this water and generate hydroelectric power, a series of dams have been built into many of the rivers. The Periyar river system, consisting of both the Periyar and Chalakudy river valleys, has many of them in a cascade. At the lower altitudes, there are a series of smaller irrigation dams and reservoirs across the state.
Since the upper dams were designed for hydroelectric generation, their management plans also focused on holding as much water as possible before releasing it. With the result, the shutters of the Cheruthoni dam were opened when they were just two feet below the full reservoir level. As the water recedes, the question that is being asked repeatedly is: why did the authorities not open these dams earlier?
Heavy rains that continued
How much did it rain this year? Was it far more than the normal? The graph computed by Indian Meteorological Departments’ Thiruvananthapuram Centre on August 20 shows that the rainfall departure from normal for the southwest monsoon season starting June 1 was only by 41.09 percent. While the state on an average should have received 1676.3 mm of rain, it received 2378.71 mm.
Even while this is a significant departure from the normal, its distribution across districts has been uneven. Idukki, which is a mountainous district, got an excess of 93.38 percent (as on 22-Aug-2018). This district received a rainfall of 3521.43 mm, against a normal of 1821 mm for the 11-week period of the southwest monsoon. This was almost close to double.
Seven districts had excess that was more than the state average. Palakkad had an excess of 73.45 percent, Kollam 54.27 percent, Kottayam 51.26 percent, Malappuram 50.81 percent, Ernakulam 48.43 percent, Pathanamthitta 47.01 percent and Thiruvananthapuram 45.33 percent. The northernmost district – Kasargod – in fact had a deficit of 11.74 percent.
The rainfall graph for every district rears its head like that of a cobra, in the last week. The week starting August 8 was when the real battering started over Kerala. It certainly turned into a one in a hundred year kind of an event that drowned the state.
Idukki is the district from which the Periyar river originates and the reservoirs are the highest in the cascade thereby flooding the others too. After a respite heavy rainfall restarted in this district, and on August 14 the shutters of the Mattupatti dam had to be opened leading to the flooding of the tourist town of Munnar. This town was preparing to welcome at least 800,000 tourists, who were expected to visit to see the kurinji flowers bloom after 12 years. Instead of welcoming tourists, the advisory was to prevent them from travelling to the hills due to the rain.
Is it the rainfall alone?
Idukki district is on the ridge of the Western Ghats with altitudes rising to between 800 to 1,000 m in the ridgelines, and the High Ranges rising to above 2,000 m. The district can be considered the water tank of the middle portion of the state with the mighty Periyar originating and flowing through the rugged terrain. Originally, the mountains would have had evergreen and semi-evergreen forests and the upper ridges would have had the shola-grassland ecosystem unique to the Western Ghats.
Streams flow from each mountain crevice and their water gathers into the Periyar system. The quality of these micro-catchments decides whether the river serves as a water tank or a cistern. Travelling on the Idukki plateau one can see streams originating either from a shola forest, or a shola-grassland converted to either mixed vegetation cardamom plantations or tea estates. Even in the worst summer, there could be some water flowing through the streams originating from a shola forest. The ones in the cardamom plantations yield less and those from tea estates would have gone dry.
It is not as if the average annual precipitation over the years has undergone a drastic change. With more forests converted to plantations or human settlements, rain water as it falls runs quickly into the streams. The water would have run down all the way to the sea, but there are reservoirs that hold its flow.
The excess rains of the past four weeks brought much of the water that fell on the Idukki hills to the reservoirs. The reservoirs had to be opened to ease pressure and there were floods downstream. The ability of the natural ecosystem to hold water and release it slowly throughout the year had been tampered with. This flood was nature’s payback time.
In the other mountainous district – Wayanad – the story is in slight variation to that of Idukki. The plantation profile is different, since in Wayanad the process of conversion from paddy fields happened in the recent decades. While historically the valleys had standing water and paddy was grown in them, Government of Kerala statistics for 2016-17 notes that the area under banana cultivation at 8,555 hectares was higher than rice area of 7,822 ha. It is estimated that the area under rice cultivation in Wayanad dropped by 37.34 percent by 2009-10 over the 1960 value.
Conversion from rice paddies to banana is a one-way process in Wayanad. Banana cultivation brings higher financial returns for the farmers. However, when banana is grown the paddy field has to be drained. The clay lining of the field dries out under the sun and thus the mountains lose the ability to soak up water as it flows into the valleys. This water rushes down the rivers and streams and cause landslides in unstable slopes. This is compounded with other land use changes such as ill-planned stone quarries and building construction across the plateau. Deaths and property destruction reported from Wayanad during the current floods were mainly due to land sliding down slopes.
An urbanising state
Increasing urbanisation in plateaus such as Wayanad also extracted its toll during the floods. Every month in Wayanad, there are new buildings mushrooming along the roads and on the slopes. Every new cut made on the soil of the hill slope adds to its larger instability. It is because of this instability that 37 out of the 67 deaths reported due to the rains between August 9 and 15 were due to landslides.
According to the Census of India report, Kerala urbanised rapidly between the 2001 and 2011 census. While in 2001 nearly a quarter of the state’s population (25.96 percent) lived in urban centres, in 2011 this had increased to nearly half (47.72 percent). The number of statutory towns plus census towns increased from 159 in 2001 to 520 in 2011.
The way the urban centres are structured is also different in Kerala compared to the other parts of the country. Instead of the usual pattern of a cluster of houses surrounded by acres of agricultural land, in Kerala, houses and urban establishments stretch in between homestead gardens and fields. Thus with urbanisation spread all across Kerala, the ecological impact of this is also universal across the state.
Affected all three ecosystems
Kerala is usually considered a flood-proofed state with its undulating terrain. For a state that receives an annual average rainfall of nearly 3,000 mm, its natural landscape protects it from recurrent floods. However, the water released from reservoirs upstream compounded the waterlogging caused by heavy and incessant rains this year.
With dams opening their shutters, the flood affected all the three ecosystems of the state – highlands, midlands and coastal plains. Even for the senior citizens of the state this was the most intense and widespread flood in their memory.
While the upper reaches were affected by release from reservoirs and landslides, in the midlands and plains the flooding was severe in areas that have either confluence of rivers or bends in them. So areas such as Ranni in the midlands and Paravoor in the coastal plains were as badly affected as the catchments in Idukki.
It is in the locations where the rivers turned (and Kerala rivers have many twists and turns) that the flooding was more severe. Thus, Annamanada on the Chalakudi and Chengannur on the banks of the Pampa took a severe beating.
More such events could come
Like with the end-2015 floods in Chennai, the intensity of the current Kerala flood is beyond what people can remember. The earlier such flood, the memory of which has come down through folklore, is the one of 1924 (1099 in Kerala calendar). Since the recent flood was unprecedented and the impact widespread, the state will remember this event even after water recedes.
While there were floods in 2018 monsoon, in 2016 both the southwest and the northeast monsoon failed in Kerala and resultantly there was unprecedented drought in 2017 summer. Even during this flood, when rain battered Kerala, the Lakshwadeep islands, which are in line for the rain clouds, have received deficit rainfall.
Even though Kerala has faced vagaries of weather in the past, the frequency of extreme weather events are becoming more intense and frequent in the recent years. As with the prognosis in the South Asian region, there could be more such events happening with intensity and frequency in the future. The 2018 flood was what could be called a one in a 100-year event. With climate change becoming a reality, the return time of such events need not be another century, but only a few decades.
It is here that the state can draw lessons from the 2018 flood. With the Western Ghats blocking the rain clouds the maximum impact was in the upper reaches of the highlands. This is the region that the Western Ghats Ecology Expert Panel (WGEEP – also called the Madhav Gadgil Committee) has covered in detail in their report. One of the strongest recommendations of the panel is to encourage and strengthen the hands of biodiversity management committees in the rural and urban panchayats to demarcate and conserve ecologically fragile areas.
If this year’s flood was a shocker, the future can be more climate resilient if grassroots communities realise the adverse impact of tampering fragile ecologies and start working for their conservation. However, their actions will need policy support and also a scientific understanding of disasters as they happened.
Ironically, even as the people of Kerala watched the water from Cheruthoni dam tumbling down the Periyar river on August 10 on television, the authorities did not have an idea on how much it would flood in Aluva and how high would the water rise. With very good three-dimension satellite maps available it is easy to have simulation exercises for situations such as this. Preparedness and drills have to become part of the system.
As the water recedes from inside buildings in Kerala the immediate tasks are cleaning up, preventing epidemics and helping people return to their lives. However, after that if there is no serious introspection on how such disasters can be avoided in the future, the lessons from this event would be wasted.
Banner image: Photo by Snehal Binil.