Dr Nater Singh
The Jammu and Kashmir state experienced catastrophic rainfall on 3rd to 6th of September. The onset of monsoon over J&K region takes place by Ist July and with draws by mid- September. On September 4th, 2014 J&K experienced 30 hours long rainfall has broken the record of many decades, the major parts of the state recorded an average of more than some aspects of catastropic rain fall in J&K rainfall. It indicates that some parts of the state has experienced more than 450 mm of rainfall in 3 days. Even moderate rainfall also recorded in Ladakh region. September was not considered rainy season in the Kashmir and Ladakh region but this year both these region have recorded heavy and moderate rainfall. Although rain in Jammu region during September was a normal phenomena but the intensity was very high. In Jammu region such huge rainfall was earlier recorded in 1903, 1908, 1926, 1942 and 1988. Kashmir valley experienced such intensity rainfall in 1903,1911,1917,1928 and 1992.IMD record reveals that Jammu and Kashmir was prone to divested rainfall and catastrophic floods in the past.
In the Kashmir valley, topography also played its role for prevailing conditions. The duration of rainfall also becomes significant when considered in relation to mean travel time of a drop of water from its point of impact on the catchment area as rainfall, to its exit from the catchment area as stream flow. In the Kashmir valley rainfall duration was greater than mean travel time with the result the whole of the catchment area of the river Jehlum considered to runoff. The time relationship between rainfall and runoff was effected by the distribution of rainfall over the catchment area. The rainfall data of September 3rd to 6th September reveals that Kashmir valley has experienced unevenly distribution of rainfall and some area experienced more than 500mm of rainfall with the results quick flow increased in stream Jehlum flow.
In Kashmir, valley shape of the catchment area of Jehlum also influenced the runoff and effected on flood intensity. Jehlum has developed a circular catchment area all the tributaries often tend to come together and joins the main stream near center of the Valley. Consequently, the separate runoff peaks generated by heavy rainfall to reach the main stream in approximately the same locality at approximately the same time caused flood intensity in the valley.
A worth mentioning phenomena was observed that there was delaying in the flood peak by one or two days. Water level of flood hit area start rising after 5th September. It was a final point, which can be made in connection with influence of drainage net work on runoff concerns. presence of Lakes (Wullar, Dal and others small lakes)played their role for delay in peak of flood. These lakes absorb (store) high runoff peaks.
Jammu and Kashmir State is vulnerable in varying degree to a large number of natural disasters. Whole state is prone to earthquake of high to vary high intensity. River Jehlum basin, Chenab basin and Tawi basin are prone to floods. During floods when flow in the river is greater than the quantity that can be confined with in the bank, the water spread out on both sides and deposits its load or silt. This is known as flood-affected area.
The catastrophic rainfall has triggered many landslides in Jammu and Kashmir region. All these landslides brought huge debris in the river basins. The slopes of steep hills of Chenab basin and Tawi basin were eroded resulting in further steepness of the banks beyond the angle of repose of the banks. On the occurrence of heavy rainfall, these banks become saturated. Water reduces the shear resistance and consequently large scale landslides occurred in the Poonch, Reasi, Doda, Udhampur and Kishtwar area. These landslides contributed a heavy quantity of debris in the water of Tawi and Chenab.
The catastrophic flood of river Tawi was the result of many natural and man made factors. The river Tawi rises from the laps of Himalayan glacier at a place named Kali Kundi and adjoining area situated on the south west of Bhaderwah in district Doda. Starting its course from an elevation of 4000 mts its bed level falls to 980 mts at Chenani after circuitous course of about 48.3 kms up to Chenani. At Chenani the river Tawi takes a south westernly semi-circular bends and flows nearly parallel to National highway up to Udhampur. In the upper catchment area maximum tributaries of river Tawi are perennial. The main tributaries like Duddar khad, Ramnagar khad, Jajhar Nallah, Salam khad, and Bamir khad contribute a sizeable discharge in the Tawi river. The total catchment area of this river from source to Jammu is 1586.32 sq km. The total length of the Tawi from Kali Kundi to Jammu is about 153.75 kms. Out of total catchment area 40 % area is below 800 meters from the mean sea level. Geomorphic study of by this author reveals that increasing sediment yield in one of the main cause of floods in the Tawi river. The relationship between sediment yield and runoff was computed and found that large scale variation in sediment yield, climate, vegetation cover, lithology and relief are controlling factors but an anthropogenic effects were more predominant causes of present flood havoc in the Tawi basin. The following factors were observed.
Sediment yield analysis was carried out , based on sediment data collected by the Central Water Commission, Cheanb investigation division which reveals that average sediment yield from 1977 to 1984 was 6503300 metric tonnes per year. At present deposition of sediments has increased many fold. The whole analysis gives a fact that sediment yield and runoff of the Tawi river are determined by precipitation or rainfall. This huge deposition of sediments in the Tawi basin has raised the river bed channel. Rising bed of the channel of the Tawi river was the one of cause of recent flood in the Tawi. Heavy rain fall on 3rd to 6th September triggered huge discharge in the river and all the drainage and sewarage links of Jammu city which were joining and flowing in the Tawi start flowing reverse with flood water which entered in the Bhagwati Nagar, Old University Campus, Commerce College, Science College, Jewel Chowk area and adjoining area. Many new colonies were developed on the old flood plain and terraces and even in side the course of the river Tawi. Flash flood has washed away all these settlements.
The catchment area of river Tawi is well marked with number of landslides which were triggered by the heavy rainfall. Heavy rainfall saturated sedimentary and loose earth material of the Tawi basin and decrease the cohesion of slope material resulting large scale landslides in the basin. The building of new roads, railway track, railway tunnels and bridges in the Tawi basin caused loading of slopes, steeping of slopes by excavation triggered landslides in the region. These landslides contributed huge amount of debris in the river water which were transported by the heavy discharge of the Tawi.
Tawi and its major tributaries presenting an interesting study of rejuvenation morphology. The formation of single terraces and tilted fans gives us clue that neo-tectonic forces are operative in the Tawi basin and effecting the fluvial processes like shifting of channels, lateral erosion and formation new flood plains.
The illegal mining and excavation in Tawi bed causing disturbance in the fluvial processes of the river with the result Tawi and many its tributaries have changed their course (channels)
Most of the old flood plain area of river Tawi like Belicharana, Chatha, Miran Sahib, Simbal Camp, and adjoining area and newly developed colonies have changed the morphology of the river. Nagrota, Gujjar Nagar, Sidhra and many colonies have occupied the flood plains of Tawi basin. New colonies like Sainik Colony, Greater Kailash, Narwal, Bathindi and adjoining colonies are developed on the unstable geomorphic landforms like piedmout fans, terraces, old landslides and old ravines. The natural drainage of these colonies were totally converted into small sewerages and concrete channels.Man has to pay the price of this change.
The influence of over grazing and deforestation in the catchment area of the basin triggered the landslides, rill, gullies and ravine erosion . The unprecedent rain fall triggered the large scale landslides in the district Udhampur, Reasi, Kishtwar , Poonch ,Rajouri and Banihal the toll was reached more 200.One of the village of Pancharri was totally washed away by a huge landslide.
The situation of Kashmir valley was very critical. In Kashmir valley streams huge deposited sediment can seen piled up at the junction of these streams. The material fan out and obstructed the flow of the river Jehlum and its tributaries. The flow in the Jehlum from Wullar lake was obstructed by the sediment heaps piled up at the mouth of the tributary stream of Pohra river. This was one of the cause of flooding of srinager valley. Also the river Jehlum was chocked by silt brought by Ningli Nallah meeting the river just down stream of the lake.
The incessant rains led swelling of rivers and rivulets across Kashmir including main river Jehlum. Breach at Kandizal and other area of Jhelum was also caused by illegal encroachments and construction along the banks of the river.
All the natural out lets of Dal lake and Wullar lake are blocked by the human construction and encroachments. The efficiency of drainage channels in the Kashmir valley were impeded by bridges, flood walls and similar structures and large scale built up area. Many big hotels and Government building are constructed on the old flood plain, old river channels and dry beds of the lakes. International conventional Centre was erected on the dry bed of Dal lake.
Small streams tributaries are infilled, while other were diverted into concrete channels/pipe/surface water gutters. All the newly developed colonies like Mahjub Nagar, Jawahar Nagar, Womena, Rambagh and other down town colonies were developed on the old channels and dry beds of the lakes. Some man made overflow channels were not properly maintained. These channels were chocked with sewerage waste and illegal encroachments with the results the intensity of the flood further enhanced. Kashmir valley have never experienced such type of catastrophe in the past. Man is changing nature with changing nature he should develop a harmonious relation with nature.
(The author is a Principal)
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