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Umkhrah : what has thou to tell?
Dondor Giri Nongkhlaw
Geomorphologist
Lately Umkhrah river has been a burning topic of discussion because of its dreadful conditions, it really is a topic of grave concern, environmentally in terms of pollution, culturally and spatially in terms of unplanned proliferation of settlements on its banks. It is a river that people have praised, that poetry have been composed and songs sung and as people have come so people have gone its name would be etched forever in the geographical landscape of the Shillong Plateau as long as it flows whether clean or dirty.
In order to understand the magnitude of its degradation we should know the names of the tributaries that empties the solid and liquid wastes, which they carry, into the main Umkhrah.
Nomenclature: The Umkhrah derives its name from two words ‘Khrud’ and ‘Rah’. ‘khrud’ means ‘to scrape or erode’ and ‘rah’ means ‘to carry or to transport’. Literally, Umkhrah means ‘the water that erodes and transport’. The name Umkhrah starts from the junction of Wahkdait just about 400 yards downstream below Kshaid Ur-Ka-Liar called by the British the Spread Eagle’s Falls and the name Umkhrah ends at the junction where it meets the Umshyrpi. These two streams Umkhrah and Umshyrpi then flow along as one river by the name of Wah Roro till it meets the Umiam-Khwan
The source of Umkhrah is the Demthring that originates north of Laitkor at a height of 6127 ft. From its source the Demthring flows along a steep slope on rocky river bed of phyllites and sandstones. On its left bank the Demthring is joined by Umkhyriem, a small rivulet of Upper Nongthymmai. The tributaries of Demthring on its right bank is Umpynthormawri that emerges from Sawlad, Um-Law-U-Sib and Wahtipthoh. As it flows downstream the Demthring meets the Umpling stream at a junction between modern day Lapalang, Rynjah and Lummarboh. The Umpling is formed by the waters of Phud Bri, Phud Pambriew and Umkoi of Nongrah and Wah Mawdamob of Happyvalley. The other smaller tributaries of Umpling are Wah Nuid, Umshyngir and Umdiengmet. Further about 400 yards downstream of Spread Eagle’s Falls, the Umpling is joined by the Wahkdait. The Wah Kdait is formed by two rivulets called Wah Ktieh that emerged from Lumbrai near Itshyrwat and Wahheh of Mawpat The name Umpling ends at the confluence where it meets the Wahnongthymmai and the name Umkhrah starts.
. The other stream on the right bank of Umkhrah is the Umlangkirding. Further downstream on its right bank there are two other tributaries, the Ummawpun that originate from Golflinks and Phudmawri of Mawlai.
On its left bank other tributaries that empty their waters into the Umkhrah are Wahnongthymmai. Wahnongthymmai has six rivulets four on the left bank and two on the right bank. These are Umpohktieh, Wahprut, Umpaitmaw, Umdiengsong and Umpyngngad, Umnongkhlaw. The source of Wah Nongthymmai is known as Umsohlwai and as it flows along it is known by the name of Umjynriew and Wahthangsning and eventually it is known as Wah Nongthymmai when it meets the Umkhrah near Demseiniong. Other small tributaries downstream is the Umnongkynrih of Laitumkhrah and Pomdngiem. The Pomdngiem has its source upslope near the Horseshoe Building between Malki point and Barik and midway down it is joined by the Umdiengsning that originates upslope flowing along the path what was known as Jacob’s ladder, now a one way metalled road. Laitumkhrah, meaning ‘away from the Umkhrah’ derived its name from the inhabitants of Mawtawar, Mawpat and Mawlynrei as they had to cross the Umkhrah upstream of the Umkhrah-Wahnongthymmai junction.
There is another stream, Umkhyrwai, that drains Nan polok and joins Umkhrah at Madan Koidi, the present day Polo Bazar. Further downstream there is another stream between Wahingdoh and Police Reserve Quarters known as Umsohsun. The Umsohsun has its source near the present Military Holiday Home opposite the Civil Hospital. As it flows along on its left bank it is joined by a small rivulet known as Umjaijai flowing down the present Them Bijoy adjoining Bawri Nethralaya. There is another stream coming from Khlieh Iewduh known as Wah Lakadeng through Them Metor that joins it near Karkhana U Bah Kon. On the right bank of Umsohsun there is a small rivulet known as Umsarang that emerged near Kelvin Cinema and flows through the Singhania Talkies and join Umsohsun down a steep slope to Wahingdoh.
Another stream known by the name Umktieh originates from Wahthapbru and flows through Madan Student to Lower Mawprem and meets Umsaw stream that originate from Khlieh Iewduh, these two joined together and is known by the name Wah Disoi and meets the Umkhrah just below the Jingkieng Mawlai.
The course or path that Umkhrah takes starts immediately just along the flat terrain about 200 metres from its source the Umkhrah flows gently toward the north east direction on hard sandstone bedrock overlying the phyllites then drop steeply on its downward journey till it reaches Jingkieng Demthring. From this point it flows on a moderate gradient and turn left at a point known as Law U Joy then again north east and flows at a moderate velocity till it meets the Umpling between Lapalang and Rynjah.
From this junction it flows in a northerly direction then it turns left in a north west direction and enters an L-shaped minor fault along quartzite bedrock aligned in a north easterly direction till just south of Kshaid-Ur-Ka-Liar. After receiving the waters of Wah Kdait on its right bank the name Umkhrah starts and suddenly takes a round left turn where it forms a U-shaped meander and flows west in a meandering manner till it meets the Wahnongthymmai.
From the junction of Wahnongthymmai the Umkhrah flows north west and its gentle flow starts from middle of the U-shaped meander and then again meanders to the left where it meets the Wah Langkirding and Umpynthor at its meandering bends on its right bank.
A little downstream after the meandering bends the Umkhrah meets the Wah Pomdngiem to form another zig zag meander and flows gently along the present Polo parking lot then turn left between the 2nd and 3rd playground and this was the actual route that the Umkhrah once took but the British excavated the present straight banks to make way for recreation such as Polo and Horse racing run by the Shillong Gymkhana.
A little south downstream, the Umkhrah meets the Umkhyrwai, originating from Nan Polok, at a place known as Madan Koidi on which today is known as Polo Bazar. From this point the Umkhrah turns west till it meets Umktieh of Police Bazar that emerge upslope of the erstwhile Singhania Cinema Hall and Umsohsun at Wahingdoh. Along this stretch, particularly on its right bank, right from Mawlai Nonglum Traisiej up to Lawmali there grown rows and rows of beautiful flowers, that bloom during March-April, known as Azaleas and the place was even known as Azalea Walk. This stretch has been a favourite place for washing, bathing and swimming for much of the people of Shillong in the past. Ironically, the KHADC has erected a cleaning up monument at the very place where Azaleas once grew which now stinks.
From the Umsohsun junction, the Umkhrah flows north in a straight course till before reaching Nonglum Traisiej where it again meanders westward adjacent Madan Weiking and then meets the Wah Disoi at Lower Mawprem and then flows steeply along quartzite bedrock to form the Beadon’s Falls and meet the Umshyrpi to flow along as one stream by the name of WahRoro. This, in short, is a brief account about the tributaries and the course on which the Umkhrah flows.
The Umkhrah has an L-shaped basin. Its basin shape is determined by its geology and topography. The basin shape can be described by outlining its watershed or water divide and for this we can trace it on the ground and can start walking from any highest point of the water divide, for this study we can start at the top of Laitkor at the height of 6234 feet above m.s.l. From this top, the water divide runs west for 600 feet where it meets the Laitkor Protected forest fire line, in fact this fire line is carved along the water divide down the ridge between Umsohlwai and Umdienglieng and then along the crest of a long tapering ridge that runs in a north east direction till Bracken Hill.
From Bracken Hill the divide runs easterly to Lumsohphoh then along the Umnongkhlaw and across the Madan Iewrynghep then to the top of Nongrimbah down to Laitumkhrah Beat House then up Nongrim Road to Nongkynrih. From Nongkynrih the water divide runs along a ridge that is aligned south west along Upland Road to Donbosco Square then through the St.Anthony’s High School to the Cathedral and Loreto Convent School up to the top of Lum Tyngkong (Lachumiere) and continuing down the Malki Point then up the Bonnie Brae Estate to Brightwell then follows the present highway from Barik Point to Anjali Petrol Pump then up the Military Cantonment to Khlieh Iewduh to Mawbah and Nongsohphoh then descent down to Kyrbom of Mawprem. From Kyrbom it follows the road to Lumsohphoh then straight down to the confluence of Umkhrah and Umshyrpi.
From the confluence, the water divide ascent a highly steep slope then turn in an arc towards Mawlai Iewrynghep along the approach road then to Mawlai Nonglum and follows the Long Round Road up to Mawroh then turn left ascending the ridge to Mawpat Peak. From the Mawpat Peak the water divide turns right along the Hare Ride to Nongkynjoin of Mawpat and again turns right to Itshyrwat. From here it ascends the Mawpram undulating landscape and then turn left to Nongrah to Mawdamob football ground of Mawshbuit.
Just before reaching Mawshbuit the water divide again turns right down slope to Assam Regiment Centre and then follows the Happy Valley Road across Madanrting to Mawblei and then ascends up the steep ridge on the right bank and culminating to the starting point. Thus based on the trail and direction of the Umkhrah watershed it is found that the Umkhrah basin covers a geographical area of 25.494 square kilometres.
Though the basin area is small in size, the basin exhibits a variety of topographic features or landform units ranging from cliffs, gentle slopes, uniform slopes, steep slopes and flat level lands and valleys, both narrow and wide and these features are distributed by nature in such a way that anyone with a keen eye for observation can notice quite easily.
It is not easy to describe the topography of Umkhrah basin in detail but the overall topographic features of Umkhrah basin is comprised of the following landform units such as cliffs, steep slopes, undulating landscape, moderate slopes and flat lands and their distribution are seen at various locations as be seen as follows.
The cliffs are seen rising, at the confluence of Wah Roro on both banks of Umkhrah, to a relative height of 210 metres upward on either side to Mawlai Iewrynghep and Mawprem. The other locales where cliffs are seen are at Riatsamthiah and Wahingdoh and along the L-shaped fault of Umpling from Kshaid-Ur-Ka Liar upstream up to the river bend near Jingkieng Umpling and at the source of Umsohlwai. These cliffs are located at different heights and of varying relative heights ranging from 8 metres at Umsohlwai to 210 metres at the confluence of Umkhrah. Other areas where cliffs are encountered are at Wah Thio, a little downstream of Jingkieng Demthring.
The steep slopes can be seen a few metres from the source and sloping steeply downstream up to Jingkieng Demthring. Another steep slope is seen along the Umsohlwai to the base of Lum Kut. Steep slopes are also encountered at the margins of undulating topography like those around Mawpat and Lumbrai near Nongmensong and around Nongrimbah at Gora Line.
The steep slopes that give rise to V-shaped valleys are seen at Wah Nongthymmai between Nongrimbah and Nongrim Hills and Wahpomdngiem along the stretch between Shillong Commerce College and Govt. lands, other location where V-shaped valley is seen is just a few metres downstream of Jingkieng Demthring.
Apart from the above topographic features, another landform that covers the greater part, about 60%, of Umkhrah basin of which it can be considered as extensive in area is the undulating topography and can be seen as situating at different levels are the extensive area from the edge of Mawroh towards the base of Mawpat ridges and the whole of Golf Links to Nongmensong. Another level is the whole of Umpling through Nongrah to Happyvalley and Law-U Sib. Another level where undulating topography is seen extends from Barik Point to Secretariat Hill encompassing the whole of European Ward to Police Bazar through Motphran to Mawkhar and Jaiaw. In fact the undulating nature of landforms in the Umkhrah basin are seen at several isolated places.
No amount of discussion, explanation or description of any of the physical bases whether topography, drainage pattern, vegetation etc will be complete without taking into consideration the geology of any area to be studied. This is because geology shapes the type of landforms, the type of drainage pattern, the type of soils and rocks which in turn influence and give rise to the various cultural activities of man.
The rocks seen in the Umkhrah basin are mostly siltstones, sandstones, phyllites and quartzites and these are widely distributed in the basin. At many places the siltstones are seen overlying the quartzites like those seen at Umsohlwai and Wahingdoh. Sandstones are also seen overlying the quartzites all over the basin like those seen in the Demthring area, Umpling, Mawpat, Nongmensong etc. Even the bedrock on which the mainstream, Umkhrah and its tributaries flow are comprised of phyllite and quartzite bedrock.
Another type of rocks are the Khasi greenstones found localized in a small patch on the right bank of Umktieh, east of Mawpat. Interestingly these are found as outcrops on a steep slope and it is the only locale where such rocks are found in the entire Umkhrah basin. These Khasi greenstones are seen overlying the sandstones and phyllites.
All these rocks are laid in different angles and position and when we study the way how the rocks are aligned and positioned we can easily tell the geological history and tectonics of the Umkhrah basin.
Physical or Morphometric aspects of Umkhrah:
i) The Umkhrah basin covers a geographical area of 25.494 square kilometres.
ii) The basin length of Umkhrah from its source to the junction where it meets Wah Roro is 13.48 kilometers. Basin length is a straight line length from the mouth of a stream to the farthest point on the drainage divide of its basin
iv) Drainage density of 2.48, drainage density is the total length of all the small and big streams in a drainage basin and is derived by dividing the total area of the drainage. It is a measure of how well or how poorly a watershed is drained by streams.
v) Basin perimeter is a measure of distance around the drainage basin and measured along the water divide and Wahumkhrah has a basin perimeter of 29.56
vi) Basin axis of 9.35.
vii Absolute relief of 1880 metres absolute relief indicates the maximum altitude of an area
viii) Relative relief of 880 metres. Relative relief is the difference between the highest and lowest point in an area
ix) Gradient ratio of 0.060, gradient ratio is the ratio of the stream gradient of a stream channel of one order to the stream gradient of the next higher order stream in the same drainage basin.
The above is an overview of the physical characteristics of Umkhrah and only when we understand its physical traits that we can plan and remedy the ills and problems that beset Umkhrah today.
Recurring floods of Wahumkhrah- In the past every year after the seven days seven nights or after the nine days nine night rains the Umkhrah overflows its banks at Polo grounds. But at present luckily such type of rainfall seldom occurs and whenever there is a heavy downpour lasting for one or two hours at Nongthymmai, Nongrah, Umpling, Mawpat and adjoining areas the Umkhrah becomes flooded. The overflowing or flooding of its banks are given as follows:
a) The existence of meanders which retard its velocity
b) The flat topography which further deter its velocity
c) Stream width becomes narrower due to proliferation and intrusions of buildings and settlements on its banks.
d) River bed becomes shallower due to sedimentation on account of the presence of stone quarries and dumping of solid wastes to the streams through the thousands of manmade cemented drains or nallas.
