Indonesian Journal on Geoscience Vol.
10 No.
2 August 2023: 229-244 Geospatial Tool-Based Geomorphological Mapping of The Lower Kulsi Basin.
India Gitika Thakuriah Faculty of Earth Science.
Geography Department.
Cotton University.
Guwahati-781001 Corresponding author: gitika.
thakuria@cottonuniversity.
Manuscript received: October, 06, 2022.
revised: January, 13, 2023.
approved: May, 14, 2023.
available online: August, 10, 2023 Abstract - Detailed geomorphological map of a region provides necessary information on landforms to understand the variations of surface and subsurface processes.
Geomorphological maps prepared based on a combined geospatial and field-observation approach are preliminary data for precise, prompt, and efficient watershed-level planning.
The Kulsi is a significant left-bank tributary of the Brahmaputra.
It has potential for agricultural, land, and water resources, but the region needs to catch up due to frequent climatic-geomorphic hazards.
Therefore, this article aims to prepare an object-oriented detailed geomorphological map using geospatial tools.
High-resolution satellite images and a digital elevation model were used to generate the detailed geomorphological map of the studied area.
The resultant map is verified with extensive fieldwork.
The investigated basin is characterized by structural and denudation hills, anthropogenetic escarpment.
pediment plain, older and young alluvial plain.
active and older flood plain.
islands and sandbar deposits, and highly sinuous river and natural and artificial surface waterbodies.
The research can contribute to local governments' and communities' land and water resource development plans.
Keywords: geomorphology, morphometry, satellite image.
Geographic Information System
A IJOG - 2023
How to cite this article:
Thakuriah.
, 2023.
Geospatial Tool-Based Geomorphological Mapping of The Lower Kulsi Basin.
India.
IndoAnesian Journal on GeoAscience, 10 .
, p.
DOI: 10.
17014/ijog.
Introduction Background Geomorphological mapping means accurately representing terrain configuration and landforms of the earth surface after systematic investigations and interpretation of morphometry, morphogenesis, morphochronology, and morphodynamic feature of landforms.
Detailed geomorphological map is a crucial parameter for sustainable land and water resources management, natural hazard assessment and management, urban development, and land use planning.
Geomorphological mapping is time-consuming, expensive, and requires extensive field observation processes prepared by well-skilled geomorphologists.
They are prepared not only for their research purposes, but pedologists, environmentalists, ecologists, archaeologists, and land planners can use it on a regional scale, such as environmental management (Cooke and Doornkamp, 1.
, land use planning (Bocco et al.
, 2.
, cultural heritage conservation (Catani et al.
, 2.
, military operation (Tate, 2006.
Peter, 2.
, soil study (Zinck, 2.
, archaeological prospecting (Van Lanen et al.
, 2.
, and urban development (Douglas, 2.
The availability of new tools such as highresolution satellite images, global positioning Indexed by: SCOPUS Indonesian Journal on Geoscience.
Vol.
10 No.
2 August 2023: 229-244 logical map of the lower Kulsi River Basin.
The geomorphic features of the basins are interpreted and analyzed using some morphometric paraA Geographical Settings Kulsi River is a northward-flowing river system that drains Assam Plain region and joins into Brahmaputra River.
The river is known as Khri in Meghalaya, where the tributaries like Um Krisinya River.
Um Siri, and Um Ngi confluence at Ukiam.
After reaching the alluvial plain of Assam, the river is known as Kulsi River.
The Kulsi Basin develops a dendritic pattern of drainage system in the upper catchment area.
The basin has a total area of around 1,953 km2.
Geographically, its latitude and longitudinal extension are 25o31ss 58.
8aa N to 26o75s 3.
33a N and 91oE to 91o48s 30a E, showed in Figure 1.
The morphology of the upper catchment area of Kulsi River is moderate to steep, and has elevations ranging from 40 m to 1,227 m above mean sea level.
The upper catchment is mainly composed of fine texture soil, the parent material is gneiss, and the downstream section of the river is covered mainly by The upper catchment area belongs to the age of Proterozoic structure, while the downstream belongs to the age of Meghalaya formed during Barpeta-I.
Sorbhog, and Hauli Formations The lower Kulsi Basin is in the subtropical monsoon type of climatic zone with highly seasonal rainfall in summer and dry winter.
The average annual rainfall was recorded at 1956.
67 mm at Boko rain gauge station located in the central part of the basin (Figure .
More than 78% of the rain occurs only in summer (May to Septembe.
, causing surface runoff and flood inundation in the lowland, vulnerability for soil erosion, and landslides on the rugged topography and flood inundation in the lowland of catchment area.
The lower Kulsi Basin is located in the southwestern fringe of Guwahati City of Assam.
The region has full urban expansion and development potential to reduce ever-increasing population pressure on the city.
systems, digital terrain models, and GIS has provided a more effective method for the acquisition, storage, and display of geomorphic features Contemporary techniques can understand surface processes more clearly in geomorphology than the traditional mapping approaches (Reddy.
GPS survey has become widespread among field geomorphologists (Cornelius et al.
A high-resolution satellite image provides detailed information on land surface features and a valuable support to the geomorphic fieldwork and interpretation of landscape on a regional scale (Rao, 2.
Multispectral and microwave sensors may detect slight elevation differences, ground irregularities, and land surface properties such as slope and dielectric behaviour of outcropping material, even in cloudy seasons (Smith et , 2.
A digital terrain model is a standard geomorphological mapping tool (Van Asselen and Seijmonsbergen, 2.
The model provides a 3D representation of the investigated area, allowing observation from different vertical scales (Teeuw.
Aringoli et al.
, 2.
Therefore, the geospatial tools are relevant for geomorphological mapping related to specialized landform study.
The method has been applied in many world regimes, and has proven effectively in a geomorphic cartography, such as the geomorphological mapping of Peru Chile Trenches (Lemankova, 2.
the coastal sector of Strandzha Mountain in Ahtopol (Prodanov et al.
, 2.
Kalamas River Delta of Epirus.
Greece (Chabrol et al.
, 2.
El Bardawil Lake of northern Siami.
Egypt (Embabi and Moawad, 2.
tropical karst environment in southern Brazil (Garcia and Grohmann, 2.
Beijing-Tianjin-Hebei area of China (Fan et al.
western Ghats Plain of India (Patel and Pati, 2.
Machoi Glacier Valley.
NW Himalaya (Pall et al.
, 2.
Rambiara River Basin of western Himalaya (Shah and Lone, 2.
Malang Regency of East Java.
Indonesia (Bachri et al.
, 2.
Objectives The present study aims to bring out a geospatial-based object-oriented, detailed geomorpho- Geospatial Tool-Based Geomorphological Mapping of The Lower Kulsi Basin.
India (G.
Thakuria.
Assam India 91o10'0"E 91o20'0"E 91o30'0"E 91o40'0"E 26o10'0"N 26o10'0"N 91o0'0"E Guwahati airport 26o0'0"N 26o0'0"N Legend Rain gauge River 25o50'0"N 25o50'0"N Sand bar Height .
n metr.
High: 1127 Low: 23 91o0'0"E 91o10'0"E 20 km 91o20'0"E 91o30'0"E 91o40'0"E Figure 1.
Location map of Kulsi River Basin (Assam part.
Indi.
contour interval of SOI toposheets.
The fluvial landforms were identified through a systematic visual interpretation of a high-resolution satellite image, i.
IRS LISS IV with 5m x 5m spatial resolution dated 26th January 2018.
The satellite image was projected at the same coordinate system unit.
WGS_1984_UTM_Zone_46N.
The current physiographic divisions were identified by superimposing the features up to the 1:5000 scale using Arc GIS 10.
6 software.
The approach Materials and Methods Material Materials used in this study are shown in Table 1 comprise seven types of data.
Image Interpretation Geomorphic Feature Identification Current physiography was delineated through the digital elevation model generated from a 20 m Table 1.
Details of Database Description Data Toposheets Source Sheet no 78 N/4, 78 N/8, 78 O/1, 78 O/5 SOI.
North East Zone Assam Nagaland GDC.
Guwahati Sheet no 78 O/2, 78 O/6, 78 O/9, 78 O/10, and 78 O/14 SOI.
Meghalaya and Arunachal Pradesh GDC.
Shillong Geomorphology Geomorphic division Geology Structure.
Lineament.
Formation.
Period Soil Soil map and characteristics National Bureau of Soil Survey and Land Use Planning, w.
Hydro-geomorphology Groundwater prospect and yield Central Groundwater Board.
Northeast Region.
Guwahati.
Rainfall Gauge Station:
Assam Plain-Guwahati airport.
Boko.
Goalpara, and Beki Meghalaya Plateau-Shillong.
William nagar, and Tikirikila.
Regional Meteorological Centre.
Guwahati.
India Regional Sericulture Research Station (RSRS).
Boko RISAT 1.
MRS 23/09/2014
Satellite image IRS LISS i, 02/10/2014 IRS LISS IV, 26/01/2018 Geological Survey of India, w.
National Remote Sensing Centre.
Hyderabad Indonesian Journal on Geoscience.
Vol.
10 No.
2 August 2023: 229-244 required steps for processing SAR images in SNAP tools are subset image, calibration, speckle filtering, and determining a threshold value for image binarization into water and nonwater.
Preprocessing calibration and speckle filtering here are done on the subset image.
The pixel values in SAR imagery can be related to the radar backscatter of the scene taken.
Calibration transforms the pixel values from the digital values recorded by the sensor into backscatter coefficient values.
Speckle filtering is just reducing the noise in the image to obtain higher-quality imagery.
By determining flooded areas .
overed by wate.
using a histogram of the filtered backscatter coefficient and applying a threshold, the water pixels can be separated from the nonwater pixels.
After determining a suitable threshold value, a binary image of water is created .
= true or whit.
and nonwater .
= false or blac.
using the band math of the raster menu.
After geometric correction of the binary image, the post processing works are done in ArcGIS 10.
6 by Export Image for Viewing in GIS.
Optical image The flood extent was delineated easily from the optical image through a systematic visual interpretation of satellite image, i.
IRS LISS i, on 2/10/2014 after seven days of heavy rainfall.
The flood-inundated areas were digitized after carefully observing the features up to 1:8000 for preparing the detailed geomorphic map of the studied area involved visual observation, preliminary interpretation using SOI topographical map and Google Earth satellite map provided by land sat/Copernicus 2021, correlation with soil texture and geological structure, and final interpretation after rigorous field check.
Flood Plain Generation Flood is an annual physio-climatic event in Kulsi Basin.
Because of high-intensity rainfall, drainage system, and discharge, physiographic conditions create massive floods, and nearby people are affected annually.
The flood plain is delineated from the flood extent of the studied area, which was generated from the satellite image.
The flood extent analysis is based on the devastating flood recorded in the last decade.
September 2014 (Figure .
Therefore, satellite data were collected during and after heavy rainfall.
During the heavy rainfall.
Synthetic Aperture Radar data of RISAT 1.
MRS on 23/09/2014 and after one weak of heavy rainfall on 02/10/2014, the optical image of IRS LISS i was collected from National Remote Sensing Centre.
Hyderabad (NRSC), (Figure .
SAR image The synthetic aperture radar image is processed using SNAP 8.
8 and ArcGIS 10.
6 software.
The Rainfal in mm Guwahati Airport
Deki bridge Shillong
Goalpara
Wiliam nagar
Tikirikila
Boko
2,84
58,12
59,12
88,37
93,52
Date 14/9/2014 - 2/10/2014 Figure 2.
Nineteen-day rainfall record before and after September 2014 flood.
Geospatial Tool-Based Geomorphological Mapping of The Lower Kulsi Basin.
India (G.
Thakuria.
Legend
Sand bar
River
Flood inundation 02/10/2014 Height in metre High: 1127
23/09/2014
Low: 23 40 km Figure 3.
Flood inundation: .
During the heavy rainfall, 23/09/2014.
After ten days of heavy rainfall, 02/10/2014.
mainly drainage density, basin relief, basin slope, dissection index, and roughness number, and the channel morphometric parameters like sinuosity index, longitudinal profile and channel gradient, and channel slopes are computed from the Survey of India toposheet at 1:50,000 scale with 20 m contour interval.
Table 2 illustrates some morphometric parameters of the basin and channels with detailed mathematical equations.
The drainage density is obtained by dividing the total length of the channel in the basin by the basin total area (Equation .
The drainage density map of the studied area was prepared using line density arc tools of GIS software.
The difference between the maximum elevation point of the catchment and the minimum height in the low-lying area is defined as the basin relief.
The DEM is the primary input for the generation of topographic information.
DEM for the studied scale using Arc GIS 10.
6 software.
The inundation layer of the flood was overlaid with the current LULC map.
The surface water bodies, especially rivers and wetlands from LULC classes were combined with the flood inundation layer to exclude them.
The whole approach for preparing an extensive studied area map involved visual observation, preliminary interpretation using SOI topographical map and Google Earth satellite map provided by Landsat/Copernicus 2021, and final interpretation after rigorous field check.
Morphometry of Landform The quantitative description of surface form is expressed by morphometry, measuring landforms (Gregory and Walling, 1.
It is necessary to express the forms of a drainage basin in the quantitative term to analyze the form-process The basin morphometric parameters.
Table 2.
Morphometric Parameter and their Mathematical Expressions Morphometric Parameter Drainage density Dd=L/A L is the total length of the stream.
A is the area of the basin Horton .
Dissection index
DI=RR/AR
RR is relative relief, and AR is an absolute relief.
Dov Nir .
Roughness number
Rn = Dd x
1000 H is basin relief
Pat t on a nd Ba ke r
Sinuosity index
SI =
CL is the length of the channel MB is the length of the meander belt axis Brice .
OIH is the change in reach elevation.
L is the total stream length from the source to the reach of interest OIL is the length of the reach Hack .
Equation
Stream length gradient
OIH x L
SL =
OIL
Description Reference Equation Indonesian Journal on Geoscience.
Vol.
10 No.
2 August 2023: 229-244 Field Survey A detailed geomorphic map prepared on the basis of the high-resolution satellite image IRS LISS IV, 26/01/2018, as well as GIS techniques are verified successfully with the help of an extensive field survey in the channel and on the The resulting map was compared with the most authenticated map with a 1:50,000 scale of geomorphic division and geology prepared by Geological Survey of India.
Whilst a Soil texture map prepared by NBSS, and information on hydro-geology of CGWB.
NER.
Guwahati.
Geomorphic features collected from the field survey are displayed in Figure 4.
area is prepared from the contours of the Survey of India topographic sheet at a 1:50,000 scale with 20 m intervals.
A slope map of the basin is prepared with the help of DEM using spatial analysis tools of ArcGIS 10.
6 software.
The slope measures the steepness or degree of inclination relative to the horizontal plane.
The slope is a vertical drop ratio to horizontal distance formed by the earth tectonic or denudation forces.
It gives necessary information on the nature of the structure and geodynamic processes at the regional level (Riley, 1.
The nature and magnitude of a terrain can be represented quantitatively through the dissection index and roughness number.
The dissection index is a ratio of the maximum relative and absolute relief.
The nature of the upland terrain of the lower Kulsi Basin is determined using the dissection index as given by Equation 2 of Dov .
and roughness number using Equation 3 given by Patton and Baker .
Channel patterns of a drainage basin are interpreted quantitatively with the help of the sinuosity index (Equation .
It is a significant morphometric parameter that affects the terrain characteristics of the river course.
The relief characteristics of Kulsi River were computed from the longitudinal It is the channel length from the source to the outlet point.
It depends on the grade of the The slope of the channel declines gradually depending on the nature of the topography and due to discharge, tectonic activity, geologic structure, sediment transport, flow resistance, width, and The river carries the materials from the source, and starts depositing the materials where the river finds the equilibrium point or the base It is the natural law of the river.
Displacement along the graded profile would indicate disequilibrium due to tectonic uplift or rock perturbations (Mackin, 1948.
Leopold and Maddock, 1953.
Whipple and Tucker, 2002.
Whittaker et al.
, 2.
A longitudinal profile measured channel gradient, channel slope, and stream length gradient index.
The stream length gradient index of the channel segments is computed using Equation 5, and the index is used for interpreting the morphotectonic evolution of the landform.
Results And Analysis Geomorphic Division Geomorphology represents a landform and topographic setting and is crucial in water resource management plans.
The detailed geomorphology of the lower Kulsi Basin was prepared based on geomorphic division and geological map prepared by Geological Survey of India, soil texture map prepared by NBSS and LUP, fluvial landforms, channel stability analysis, and flood extent from Spatio-temporal satellite The main geomorphic feature in the lower Kulsi watershed is structural and denudation hills, pediment plain, alluvial plain, sand deposits, and surface water (Figure .
Table 3 illustrates the areal extent of detailed geomorphic division, subdivision, soil texture, hydrogeology, and groundwater prospect.
The topographic, drainage, soil, and other condition of each geomorphic feature are discussed below.
Denudation and Structural Hills The upstream of the studied area comprises moderate and highly dissected structural hills, and the low and moderately dissected denudation hills are low-relief isolated hills in the pediment complex.
The relief characteristics of the lower Kulsi Basin are shown in Table 4.
Due to continuous erosional processes, the denudational hills have Geospatial Tool-Based Geomorphological Mapping of The Lower Kulsi Basin.
India (G.
Thakuria.
91o0'0"E 91o10'0"E 91o20'0"E 91o30'0"E 91o40'0"E 26o0'0"N Stream 20 km Riverine Wetland Floofed Wetland River Island Depressional Wetland Natural Levee Slope Wetland Active Flood Younger Alluvial Plain Tectonic Wetland Flood Plain 25o40'0"N Ox Bow River Sand Bar 90o50'0"E 25o50'0"N Legend:
Escarpment (Anthropogeni.
Vernal Pool Highly Dissected Structural Hills and Valleys Wet Meadow Older Alluvial Plain Moderately Dissected Structural Hills Marshy Land Piedmont Peneplain Moderately Dissected Denudational Hills Pond Piedmont Alluvial Plain Low Dissected Denudational Hills 91o0'0"E 91o10'0"E Figure 4.
Detailed geomorphologic division map.
Waterlog 91o30'0"E 91o40'0"E Piedmont Plain The pediment plain is another crucial geomorphic basin unit with a moderate slope sustaining natural vegetation and grassland at the base of the moderately and highly dissected parts of structural Garo Hills.
The piedmont plains are subdivided into two geomorphic units: The piedmont alluvial plain and the piedmont peneplain.
Piedmont alluvial plains are the deposited landforms created at the foot of Garo Hills by Kulsi and its numerous tributaries.
Piedmont peneplain is the gentle undulation low featureless plain produced by fluvial erosion.
The elevation of the piedmont plan area varies from 36 to 85 m above mean sea level.
The landform supports the natural vegetation of Tectona Grandis (Tea.
and Shorea Robusta (Sa.
species with extensive grassland.
The drainage density of the region varies from 58 to 1.
10 km/km2 (Table .
a comparatively lower average slope and lower relief landform.
The elevation of the denudational hills of the lower Kulsi Basin varies from 41 m - 212 m above mean sea level.
The hills are low to moderately dissected by small streams.
The drainage density of the region is very low, 0.
to 1 km/km2, while the high dissection index of 48 and roughness number 7.
45 - 9.
62 represent highly erosional land surface due to fluvial action.
The average estimated rate of soil loss is about 02 t ha-1y-1.
The southern hill features are controlled by the underlying geological structure of amphibolite, dolerite, and grey and pink porphyritic granite.
The elevation of the structural hills varies from 48-1127 m above mean sea level.
It is a moderate to a highly dissected hill by numerous streams where the dissection index is found at 49 - 0.
53, and the high drainage density varies 62 to 2.
68 km/km2, with the average slope 62 degrees, depicting the surface runoff of the rugged hilltop, and are affected by soil erosion.
Anthropogenic processes interrupt or break the general topographic continuity of the land surface and produce a relatively steep slope-0.
31 km2 area covered by the anthropogenic escarpment.
91o20'0"E 25o40'0"N 25o50'0"N 26o0'0"N 26o10'0"N 26o10'0"N 90o50'0"E Alluvial Plain The low-lying area of The Kulsi Basin is an alluvial plain.
The geomorphic subunits of the plain are the younger alluvial plain, older alluvial plain, active flood plain, and older flood plain.
Indonesian Journal on Geoscience.
Vol.
10 No.
2 August 2023: 229-244 Figure 5.
Photographs of: .
Highly dissected structural Garo Hills and Kulsi River at Ukium.
Overview of hill, piedmont alluvial plain in Kulsi Basin.
Older alluvial plain in between Sal Forest dominated the piedmont alluvial plain.
Sal Forest dominated piedmont peneplain complex with older alluvial plain.
Bamboo-dominated peneplain feature with paddy field on the young alluvial plain.
Sand bar formation in the bed of Kulsi River near Ukiam.
Anabranch of Kulsi River near Nalbari Forest Village.
Formation of river island near Balijori Village by anabranch channel of Kulsi River.
River Island in Singra River, a tributary of Kulsi River.
Wetland at the foothills of Gobardhan Hill.
Gabong slope wetland at the foothills of Kulsi Hill.
Depressed wetland in Dhanubhanga Reserve Forest.
Wet meadows in Deosila Reserve Forest.
Grazing land surrounding the Dora wetland.
Flood Inundation in Sontali Village .
Flood impacts on domestic animals.
Sontoli Village .
The structure of older alluvium is oxidized to feebly oxidized sand, silt, and clay and highly oxidized, dark brown to red-brown in loamy The composition of the younger alluvium is feebly oxidized sand, silt, and clay and white to greyish-coloured sand, silt, pebble, and clay.
The slope gradient of Kulsi River from Ukium .
to Nagarbera .
abruptly falls about 46 cm/ Table 5 shows the relief and drainage characteristics of the alluvial plain of the studied area.
Flood is a significant problem in the studied area, identified as active flood areas, chronically Geospatial Tool-Based Geomorphological Mapping of The Lower Kulsi Basin.
India (G.
Thakuria.
Table 3.
Areal Extent of the Large-scale Geomorphological Map of Lower Kulsi River Basin Geomorphic Areal extent .
Landform unit Highly dissected structural hills Soil texture Moderately dissected structural hills 415.
Piedmont Plain Alluvial Plain Surface Sand deposits Moderately dissected denudational Fine Low dissected denudational hills Escarpment (Anthropogeni.
Piedmont alluvial plain Fine Piedmont peneplain Fine.
Coarse & Fine loam Older Alluvial Plain Fine clay & Fine Young Alluvial Plain Coarse Silt Flood Plain Coarse Silt.
Fine Active Food Plain Coarse Silt River Wetland Marshes Sandbars River Islands Natural levee Groundwater is restricted to 50 m depth in weathered residues, joints, and fractures having secondary Thickness in the weathered zone 5-15m.
Low yield prospect up to 5 m3/hr.
Dug wells are feasible in weathered zones.
Boreholes at fractured zone at selected points Moderately thick but discontinuous confine & unconfined aquifers, a thickness of 10-50m within 50-100m depth.
Suitable for shallow tube well with a yield of 10-20 m3/hr.
Deep tubewell up to 100 m depth, yielding 30- 50 m3/hr.
Dug well feasible at foothills Relatively thick and regionally extensive confine & unconfined aquifers.
Aquifer thickness, 30-70m within 150-300m depth.
Large yield prospect Suitable for shallow tube wells with 30-50m3/hr.
Deep tube wells of 150-200 m depth yield 50-150 m3/hr.
Relatively thick and regionally extensive confine & unconfined aquifers.
Aquifer thickness, 30-70m within 150-300m depth.
Coarse Silt Total area Groundwater prospect Hill Hydrogeology Large yield prospect Suitable for shallow tube wells with 30-50m3/hr.
Deep tube wells of 150- 200 m depth yield 50-150 m3/hr.
Table 4.
Landform Units of Hills and their Relief and Drainage Characteristics Landform units Max.
Relative Drainage density .
m/ Average Slope (Degre.
Dissection Roughness Min.
Highly dissected structural hills Moderately dissected structural Moderately dissected denudational hills Low dissected denudational hills Height .
Areal extent .
Table 5.
Landform Units of Pediment Plain and their Relief and Drainage Characteristics Landform units Areal extent .
Piedmont alluvial plain Piedmont peneplain Height .
Relative relief .
Drainage density .
m/km.
Min.
Max.
flooded areas, and occasionally flooded areas (Figure .
Flood occurrences are a natural annual event of the alluvial plain.
The area represents a highly vulnerable Kulsi River flood plain, dev- astated almost annually by floods.
These areas are dense populations, and it is observed that the intensity of floods is increasing with time and with a more significant loss.
Indonesian Journal on Geoscience.
Vol.
10 No.
2 August 2023: 229-244 Table 6.
Landform Units of Alluvial Plain and their Relief and Drainage Characteristics Landform units Older Alluvial Plain Young Alluvial Plain Flood Plain Active Food Plain Areal extent .
Height .
Min.
Relative relief .
Drainage density.
m/km.
tectonic activity, geologic structure, sediment transport, flow resistance, width, and depth.
Meghalaya, the river origins at an altitude of 1,700 m near Nonglyer .
nown as Khri Rive.
, the tributaries like Um Krisinya River.
Um Siri, and Um Ngi confluence with Khiri River at Ukium.
After reaching the alluvial plain of Assam, the river is known as Kulsi River.
It runs up 83 km at the outlet point.
Figure 6 shows that the Knickpoints about 15.
98 km and 53.
km downstream from Nonglyer are presumably due to the Guwahati Fault passing along Kulsi River course (Yin et al.
, 2.
On the other hand, the third knick point about 10 km upstream of Ukiam corresponds with the lithological boundary between a Banded Gneissic Complex of Shillong Plateau and the alluvial Assam plain associated with high stream length gradient indices upstream, indicating the tectonic activity in faster erosion (Imsong et al.
, 2.
Table 8 illustrates the slope gradient and stream length gradient index of Kulsi River from Ukium .
to Nagarbera .
, abruptly falling about 41 cm/km and 0.
02, respectively.
The Kukurmara site, about 33.
66 km downstream from Ukium reach, has a slope gradient of about 0.
98 m/km, indicating that the upstream highly eroded materials are deposited in the downstream and lower course.
Surface Water River Kulsi River is located on the northern front of Shillong Plateau.
It originates from the Meghalaya Plateau at 1,700 m above mean sea level in Meghalaya, known as the Khri River.
After reaching the alluvial plain, the tributaries, namely Um Krisinya.
Um Siri, and Um Ngi, confluence with the Khri River at an altitude of 80 m above mean sea level near Ukiam of Assam.
The river is known as Kulsi River.
It flows towards the north and drains in the plain region of Assam into Brahmaputra River.
Um Krisinya.
Um Siri.
Um Ngi.
Boko.
Singra.
Singua, and Deosila are left-bank tributaries of Kulsi River.
Batha and Umshru are two important tributaries on the right bank.
Kulsi and its tributary and anabranches occupy about 05 km2 geographical area.
It develops a dendritic pattern of the drainage system in the upper catchment area.
As the per stream order method of Strahler, the Kulsi is a ninth-order drainage system.
In the lower Kulsi River Basin, 1910 stream segments are delineated in the first order (Table .
The debris slopes are moderate to severely eroded with finer alluvial soil high acceleration.
The sinuosity index of Kulsi River between Balijori and Brahmaputra confluence near Nagarbera, about 71 km channel reach, was found at 1.
24 in the year 1972 and 2018, respectively.
shows that the downstream of Kulsi River is highly From Ukium to Balijora, about 22 km, the sinuosity index wasrecognized to be 1.
10 in 1972 05 in 2018.
Here low sinuosity index specifies solid structural control and flows over Kulsi Fault line from an approximately straight channel.
Max.
Relief Characteristics of Kulsi River Slope declines gradually depending on the nature of the topography and due to discharge.
Wetlands Wetlands cover about 51.
89 km2 area of the lower Kulsi River Basin.
Based on geomorphic settings, the wetlands of Kulsi River basin are classified as riverine, slope, depressional, vernal pool, marshes, and pond (Table .
Riverine wetlands occur in the low-lying flood plains, water blocked in paleochannels, and riparian pathways associated with stream Flooded and oxbow are examples of Geospatial Tool-Based Geomorphological Mapping of The Lower Kulsi Basin.
India (G.
Thakuria.
Table 7.
Landform Units of Surface Water Landform units Areal extent .
River Nonglyer .
Ukiam .
incapable of depressional storage, because they necessarily lack closed contours.
Slope wetlands can occur in nearly flat landscapes if groundwater discharge is a dominant source of the wetland Slope wetlands lose water primarily by saturation subsurface and surface flows and Depressional wetlands develop in topographic depressions after precipitation, groundwater discharge, and interflow and overland flow from the surrounding uplands toward the centre of the depression (NRCS, 2.
Depressional wetlands may have any combination of inlets and outlets or lack them entirely (NMED.
Tectonic wetlands due to by the tectonic movement-Chandubi wetland of Kulsi watershed formed as the tectonic submergence of forest during earthquake in 1897.
Vernal pools are present as small topographic depressions and isolated wet areas within upland forests with poor drainage, where runoff from rain Elevation .
Number Kulsi Number of segments Wetland Classification of geomorphic unit Mainstream Tributary Anabranch Streams order First Second Third Forth Fifth Sixth Seventh Eighth Ninth Riverine Oxbow lake Flooded Slope Depressional Tectonic Vernal pool Marshes Wet meadows Waterlog Pond Nagarbera ( 35 .
Distance .
n k.
Figure 6.
Longitudinal profile of Kulsi River shows major Knickpoints and a high stream gradient in the upper course.
riverine wetlands.
Flooded wetlands are formed by overbank flow or subsurface hydraulic connections between the stream channel and wetlands (NRCS, 2.
Oxbow lakes are crescent-shaped riverine water bodies and abandoned meander loops of a channel.
It is formed as the river cuts through the meander neck to shorten its course and block off sediment deposits.
Slope wetlands commonly lie on sloping land where groundwater is discharged to the land surface (NRCS, 2.
They are usually Table 8.
Relief Characteristics of Kulsi River Computed from Longitudinal Profile Name Nonglyer Ukiam Kukurmara Chamaria Nagarbera Elevation .
Stream length .
n k.
Channel gradient .
/k.
Stream length gradient index Indonesian Journal on Geoscience.
Vol.
10 No.
2 August 2023: 229-244 Discussion The field-based geomorphological mapping is time-consuming, cost-intensive, qualitative, and difficult to reproduce (Meij et al.
, 2.
The development of satellite imagery.
GPS, and GIS modelling techniques has opened up new opportunities for applied geomorphological surveying and mapping.
The combined geospatial tools and field observation-based techniques create an accurate and precise geomorphological map.
The past works of literature show that the rapid geomorphic regionalization of the Beijing-Tianjin-Hebei area of China was achieved based on digital terrain analysis through the development of remote sensing and GIS (Zhang et al.
, 2.
field and geospatialbased geomorphological map of Kalamas Delta contains lithology and hydrogeology (Chabrol et , 2.
the geomorphic features of El Bardawil Lake of northern Sinai in Egypt was presented using digital image processing techniques (Embabi et , 2.
, the large scale geomorphological map with 1:10,000 scale was created based on digital elevation model for karst environment in southern Brazil (Garcia and Grohmann, 2.
The remote sensing and GIS-based regional geomorphological map can be utilized for land evaluation and land use planning (Bocco et al.
, 2.
The Kulsi Basin is located in the undulating topography with highly seasonal rainfall in summer and dry winter.
Below 1% of the total rainfall occurs only in the winter (December to Februar.
causing issues with water shortage, groundwater recharge and discharge in the basin.
More than three-fourth of the rain occurs only in summer, leading to surface runoff and flood inundation in the lowland, vulnerability for soil erosion, and landslides on the rugged topography in the catchment.
Therefore, the Kulsi Basin of north-eastern India needs large-scale object-oriented landform information for watershed management.
In this research, the geomorphic map of the basin was prepared using high-resolution satellite data .
for the first time with reasonable accuracy of the feature observation and 20 m contour DEM for calculating the topographic collects in spring (Thomson and Sorenson, 2.
They are flooded temporarily for a short time after heavy rainfall every year.
Most of the wetlands on the piedmont alluvial plain with dense vegetation covering Kulsi watershed are categorized in the vernal pool.
Marshes are characterized by standing water and emergent vegetation (ANR) such as water hyacinth (Eichhornia crassipe.
, lotus (Nelumbo nucifer.
, water lillies (Nymphaeacea.
, water caltrop (Trapa natan.
, and water spinach (IpoA moea Oquatic.
The plants that grow in marshes vary depending on the water depth and the duration of flooding.
Wet meadows and marshes of 99 km2 wide are also identified in the lower Kulsi Basin.
It is a type of wetland with watersaturated soil supporting grass growth.
They are found in the riparian area and land between marshes and upland.
Ponds are natural or artificial shallow and small inland standing water bodies.
Two hundred thirty-two smaller natural and artificial ponds are identified in the lower Kulsi River Basin.
Sand Deposits The Kulsi and its tributaries deposited numerous coarse sand bars along the bank and bed of channels due to decreased stream velocity when they enter gentle sloping foothills.
Three hundred ninety-eight sand bars were found in the lower Kulsi Basin covering 25.
7 km2 in 2018.
Small river islands are formed by anabranches along the unstable banks and return to the mainstream further downstream.
Twenty-one small and large river islands were formed, covering a 30.
km2 area in the Brahmaputra and its tributary.
Kulsi.
It has three river islands by an anabranch channel process near Balijora.
Ghormara, and Karidal Villages.
The formation of natural levee is another essential characteristic of the Kulsi and its tributaries in the alluvial plain.
It is a long, broad natural embankment of sand and coarse silt, built by streams on a flood plain and along both sides of its channel, especially when water overflowing the normal bank is forced to deposit the coarsest part of its load.
Geospatial Tool-Based Geomorphological Mapping of The Lower Kulsi Basin.
India (G.
Thakuria.
Acknowlwdgement The author would like to thank the Science and Engineering Research Board (SERB) for its financial support on this project.
Special thanks to the scientists of the Regional Sericulture Research Station (RSRS).
Boko, for providing rainfall and other meteorological data.
The author is thankful to wonderful field assistants, research scholars, and all who indirectly contribute in making this research successful.
Conclusions River plain.
A detailed geomorphological map can be applied as a preliminary input for watershed management, land and water resource action plans, water harvesting site delineation, potential groundwater zonation, flood and landslide hazard risk management, optimum land use planning, and urban expansion and development of Kulsi Basin.
Therefore, the research will contribute to developing the country local governments and communities if the large-scale geomorphic map is used for the land and water resource development plan.
The geomorphic features were digitized after carefully observing the features up to the 1:5000 scale using Arc GIS 10.
6 software.
The correctness of the landform features derived from satellite images was assessed using the point-bypoint method to show similarities and differences between the output and geomorphic division of the geological survey of India map layer.
The overall accuracy was 0.
95, indicating almost perfect strength of agreement between the output feature and ground truth data.
The proposed largescale geomorphic map prepared based on remote sensing, and GIS techniques offers input to land and water resource management of the lower Kulsi Basin.
The proposed map would help the decision-makers, urban planners, and local government as an input database to achieve sustainable development and reduce meteor-geomorphic hazards of the basin.
Detailed geomorphological maps act as an essential input in land and water resource management, urban planning and development, hazard risk reduction by demarcating hazard zoning, potential groundwater assessment, and another environmental research.
The detailed geomorphological map of Kulsi Basin was performed based on the combined geospatial tools using high-resolution satellite data in Arc GIS 10.
8 software and field observation.
The resultant geomorphological map of the studied area was further compared with most authenticated governmental datasets, records, and maps.
About 30 % of the studied area comprises moderate to highly dissected structural hills, low and moderately dissected denudation hills, and low relief isolated hills in the pediment The lowland includes the piedmont plain and the alluvial plain.
The alluvial plains are categorized into the younger alluvial plain, older alluvial plain, active flood plain, and older flood plain with a channel gradient of 0.
46 m/km.
Temporary sand deposits, river islands, and natural levees are micro- geomorphic features of Kulsi
References