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On June 28, a Sunday, a large expanse starting from Pasighat in Arunachal Pradesh (AP) up to the outskirts of Silapthar in Assam was inundated within hours.
Floods are not new to this region. But what made this flood unique was the fact that Assam and AP have remained rain deficit from June 1-23 during the present monsoon session. However, intense rains within a short period made a network of rivers originating in the eastern Sub-Himalayan region swell and wreak havoc.
Pasighat (East Siang district) of AP recorded 222.8 mm of rain in 24 hours during June 28-29, an obvious extreme rainfall event which went down to 9 mm during June 29-30. A Sandeep, head of meteorological center Itanagar (AP) told Down To Earth (DTE) that although no cloudburst was recorded, the active monsoon caused incessant rain in the last 48 hours prior to flooding.
Sarat Phukan of Gauhati University explained that many small Himalayan and sub-Himalayan rivers entering Assam from Arunachal Pradesh can trigger sudden flash floods because their upper catchments lie in the high-rainfall foothill belt, where monsoon winds strike the mountain front and produce intense orographic rainfall.
“Unlike large rivers such as the Brahmaputra, Subansiri or Kameng, these smaller rivers are short, steep and narrow, with limited channel capacity and little space to store or spread-out sudden storm runoff. Large rivers have wider channels, broader floodplains and longer flow paths, so flood waves are generally delayed and partly attenuated as they move downstream. But in smaller foothill rivers, whose catchments are mostly spread across the high-rainfall foothill belt, heavy rain within a few hours or a cloudburst-like event can quickly generate fast-moving runoff and sharply raise the water level,” Phukan said.
“The danger is increased by the fragile foothill terrain, especially where rivers cut through the young, weak sedimentary rocks of the Siwalik Group, composed mainly of easily erodible sandstone, siltstone, mudstone and conglomerate. During heavy rain, these slopes can supply large volumes of sediment, debris and sometimes landslide material into the channels. At times, such debris may temporarily block a river and then suddenly breach, adding another surge of water and sediment. Thus, flash floods in these small rivers usually result from the combined effects of intense, short-duration rainfall over foothill catchments spanning some of the most rainfall-prone zones of the eastern Himalaya, together with steep, narrow channels, rapid runoff, fragile rock, high sediment loads, and occasional blockage-breach events,” he added.
In Arunachal, the big river Siang caused no considerable flood, but other small rivers and channels did. Kalom Taggu, a resident of Yagrung said his village was inundated by the Tolon Korong (Korong means river in the Adi language).
The other rivers that caused floods are the Sibo Korong, Poglek, Sille, Dura and Yembung. “Sibo flooded Sibo Siang colony in Pasighat and Boying village,” Taggu, who is also the president of All Yagrung Students’ Union and has been engaged in relief work, told DTE. He added, “It was in 2000 that we saw a massive flood caused by the Siang and no flash flood of this scale exists in our recent memory.”
Augusty Lego, a local reporter who is on the ground for impact assessment, verified Taggu. She said the Sibo flooded the Yapgo as well. “Ledum is worst affected, caused by sudden swelling of some small streams and the Dobung Korong bridge has been damaged by the Dobung river which connects east Siang and lower siang,” said Lego.
Coming down to Assam, Jonai district has been badly affected by the Leku, Sille and Kemi rivers. The swelling Kemi river washed away the Kemi-Puroni Jelom iron bridge. However, the Oiramghat area is flooded by the Siang river, said Taburam Mili, a local resident of Puroni Jelom in Jonai.
Mili told DTE that at around 3.30 PM on June 28, a massive gush of water entered the villages in no times. “Adi Leku, Puroni Jelom, Kemi, Oiramghat areas are severely affected for two days and now the water is receding. Our villagers didn’t get any time to rescue their belongings,” he said.
Aseng Mili, a PhD research scholar at Gauhati University who is also from Jonai, added that the Oyan river has caused flood in villages like Oyan Jelom and sirung. “Local streams have created floods in the Bahir Jonai area. The scale of this flood is reminiscent of 2003, when we witnessed havoc due to flood,” Aseng added.
The most discussed scene of the flood in Assam was the destruction of a railway bridge over the Simen river. This bridge is the only means of railway connectivity to the last point of Assam, Murkong Selek.
Sujit Hajong, a former village panchayat president of Simenmukh, described the situation to DTE: “The scenario can’t be described in words. We were at the banks of the Simen river to see its rising level. But suddenly, at around 11 AM, something unusual happened. We saw that a wall of water, probably 10 feet above the river surface gushed in. This capsized a pillar of the railway bridge and tilted it and within moments, the bridge collapsed.”
“In my lifetime I haven’t seen such huge water coming suddenly into the Simen river. Over 30 villages are affected in the Simenmukh area. The paddy saplings that were to be planted in the fields, are all gone as well as livestock. I think in 13-14 villages, there will be no rice production or very less even if people plant new saplings. The loss is unmeasurable,” Hajong said.
Rini Saikia, a faculty at Simen Chapori College, commented, “There are huge extractions from the Siemen river, be it boulders, sand or pebbles. The river has silently fed many and when they crossed the limit it showed its wrath.” She added that she hasn’t witnessed the Simen ravaging in this manner in her life.
Flooding by the Simen river is not unusual. But this time, the scenic river took a horrific form.
Phiroz Handique, an employee of the same college, told DTE that apart from the Simen, the Dikhari river has also caused flood damages in the nearby areas. “However, the Simen Chapori area remains unaffected,” he said.
Downstream of Simen Chapori, villages like Rongpuria, Sengajan are affected due to the Simen flooding.
Dams or hydroelectric power projects have been an issue of serious concern in Northeast India, with wide scale resistance against them. Massive protests last year against a proposed dam over the Siang river is still fresh in memories of the people of Arunachal Pradesh.
The current flash flood triggered the same concern again. In social media, many from Arunachal have raised concerns about the possible devastations if big dams are built like the one over the Siang.
Ebo Mili, a lawyer by profession and a strong voice against dams, commented: “In 2023, we saw the condition in Sikkim due to the dam over the Teesta river. The GLOF (glacial lake outburst flood) was the main cause of breaking of the Teesta dam. Why don’t dam developers consider that in Arunachal as well? We have seen this year how small rivers and channels can cause devastations due to extreme rain. What if a GLOF strikes Arunachal? Moreover, the extreme high tendency of landslide places Arunachal in another level of danger. The Upper Siang is in A category of danger. Even then, how can a big dam like the proposed one over the Siang be thought of?”