Geomorphometric Analysis for Estimation of Sediment Production Rate and Run-off in Tuirini..

International Journal of Remote Sensing Applications (IJRSA) Volume 5, 2015 doi: 10.14355/ijrsa.2015.05.008

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Geomorphometric Analysis for Estimation of Sediment Production Rate and Run-off in Tuirini Watershed, Mizoram, India Fuzal Ahmed, K. Srinivasa Rao Department of Geology, Mizoram University, Tanhril Campus, Aizawl – 796004, Mizoram, India fuzalahmed@gmail.com Abstract In hilly areas like Mizoram, sediment production rate and run-off estimation for land parcels is of utmost importance to the efforts of soil and water conservation work. The study demonstrated the use of remotely sensed data in conjugation with GIS for the sustainable development of watershed. The terrain is prone to erosion due to steeper slopes associated with high relief and drainage density. The different geomorphometric parameters of the study area have been computed with the aid of ArcGIS-10.2 software. SPR and run-off rate of the watershed was estimated on the basis of morphometric parameters.

The Tuirini watershed is designated as 6 th order stream comprises an area of about 420 sq.km. The mean bifurcation ratio indicates strong structural control over the drainage development. The values of drainage density and texture ratio indicate that the area is composed of impermeable rocks associated with very fine drainage texture. The analysis of shape and relief parameters shows that watershed is having elongated shape and structurally complex with high relief. The estimated value of SPR and run-off rate suggests that the watershed produces moderate amount of sediments annually with high discharge of runoff due to high relief with steeper slopes.

Key words Geomorphometric Parameters; Sediment Production Rate; Run-off Rate; GIS; Remote Sensing; Tuirini Watershed; Mizoram

Introduction The hilly terrain of Mizoram is prone to soil erosion due to soft nature of sediments, immature topography, heavy rainfall, high drainage density and high relief with steep slopes. A large amount of eroded sediments outflow from the watershed every year, particularly during the monsoon. The area is represented by a complex structural deposition of argillaceous and arenaceous sediments of Neogene deposits. Estimation of soil erosion, sediment production rate (SPR), runoff, sediment transportation and deposition within a watershed are essential for conservation of land and water resources to sustain any developmental activity carried out on a watershed.

Management of natural resources at watershed scale produces multiple benefits in terms of increasing groundwater storage, utilizing runoff for useful purposes, minimizing land degradation and controlling soil erosion to reduce the effect of sediment yield on the watershed. Watershed is a technical term used to denote a common drainage point. It is land area that captures precipitation in the form of rainfall, snow or dew and drains water and sediments through a common outlet at which the water enters another water body such as a stream, river, lake or ocean. Watershed characteristics such as size, drainage, climate, lithology, vegetation, slope, land use/cover and soils affects peak rate of runoff, infiltration rates, erosion and sediment production.

Geomorphometry is the numerically analysing and quantifying of the land surface. Geomorphometric analysis of a watershed gives reliable information about hydrogeological nature, geological structures, slope morphometry, surface runoff, stream discharge and sediment yield etc., which helps for effective planning, development and management of natural resources of an area. Land degradation due to weathering and erosional process produces sediment load which is transported by surface runoff into the river or ocean. The amount of detached sediment load traversing through the outlet of a watershed is known as sediment yield. Sediment yield and runoff of a watershed are influenced by lithology, vegetation, soil, slope and rainfall intensity. For estimating soil erosion from the watersheds, several empirical models based on the geomorphological parameters were developed in the past to quantify the run-off and sediment production rate (Jose and Das, 1982; Misra et. al., 1984). Remote sensing and Geographic Information System (GIS) are the most advanced techniques for watershed management, planning and 67

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development. The present study was taken up to estimation of various geomorphometric parameters, SPR and run-off using GIS tools for further planning and management of resources for sustainable development of the watershed.

FIG.1: LOCATION MAP OF THE STUDY AREA

Description of the Study Area The study area, Tuirini watershed is located in the Aizawl and Serchhip districts of Mizoram in north-east India, stretching between longitudes 92o49′34′′– 92o58′22′′E and latitudes 23o28′37′′– 23o53′20′′N (Fig. 1). The geographical area of the watershed is about 420.07 sq.km with a maximum length of 45.30 km from north to south and the maximum width of 11.5 km from east to west. The watershed has an elongated shape in the south-north direction and elevation ranges from 1905 to 78 m from mean sea level. The entire study area is hilly terrain and the hills ranges are parallel to sub-parallel, trending almost N-S direction. The soils of the watershed are mostly of red and yellow loamy with acidic in nature. The study area falls under the direct influence of south-west monsoon.

The watershed receives an average annual rainfall of about 2300 mm and 80 % of the rainfall occurs during the monsoon season from June to September. The average summer temperature is about 25°C and average winter temperature is about 18°C of the study area.

Lithology of the Study Area Geologically, the study area belongs to Middle Bhuban and Upper Bhuban Formations of Surma Group of Lower Miocene-Middle Miocene in age. The sedimentary rocks exposed in the study area are thickly bedded sandstones, shales and siltstones and their various intermixtures in varying proportions. The Middle Bhuban Formation is conformably overlain by the Upper Bhuban Formation with gradational and transitional contact. Middle Bhuban Formation is mainly argillaceous with shale as the dominant rock type. It composed of assemblage of shale, siltstone, sandy-shale and silty-shale with subordinate amount of sandstones. Upper Bhuban Formation is mainly arenaceous with sandstone as the dominant rock type. This unit comprises of sandstones with subordinate amount of shale and siltstones alternations. In the study area most dominant rocks are shales and siltstones which covers an area of 274.03 sq.km (65.24 %) and minimum area is occupied by sandstones i.e. 146.04 sq.km (34.76 %) of the study area (Fig. 2).

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FIG. 2: LITHOLOGICAL MAP OF THE STUDY AREA

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FIG. 3: DRAINAGE MAP OF THE STUDY AREA

Types of Drainage Pattern in the Study Area The role of lithology and geological structures in the development of stream networks can be better understood by studying the nature and type of drainage pattern (Nag and Chakraborty, 2003). The spatial relationship between streams or rivers in a particular drainage basin constitutes the drainage pattern. The drainage pattern of an area reflects the nature of slope, geological structure and lithologic controls of the underlying rocks (Zernitz, 1932 and Easterbrook, 1969). Drainage patterns of the study area have been observed as mainly trellis type while in some parts of the watershed represents parallel and dendritic types, which are described below:

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FIG. 4A: TRELLIS PATTERN

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FIG. 4B: PARALLEL PATTERN

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FIG. 4C: DENDRITIC PATTERN

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a) Trellis pattern: Trellis pattern is characterised by elongated tributaries flowing parallel or sub-parallel to the major stream. The primary and secondary tributaries join the major river at approximately 90 0 angles.

Such patterns are developed in the areas of folded sedimentary rocks of various resistances to erosion. In the study area trellis is the most dominant pattern and occupies about 92% of the area due to the presence of folded bedrock of varying resistance and might be strong structural control upon streams (Fig. 4A). b) Parallel pattern: The parallel drainage pattern comprises numerous streams flowing nearly parallel to each other and all the streams join the main channel at approximately the same angle. Parallel drainage patterns are found in areas where regional slopes are dominant and also in regions of parallel elongate landforms.

In the NE, SE and SW parts of the study area, some of the streams show the parallel type of drainage pattern due to steep slopes and covers an area of about 6% (Fig. 4B). c) Dendritic pattern: Tree like branching of streams and rivers that intersect primarily at acute angle is defined as dendritic pattern. It indicates the homogeneity in texture, rock type and lack of structural control. Dendritic to sub-dendritic pattern is observed in the limited part of the study area and constitutes about 2% of the area because of its uniformly resistant and homogeneous nature of the rocks (Fig. 4C).

Materials and Methods Three types of data sets have been used in the present study: (i)

Survey of India topographic (SoI) maps on 1:50,000 scale bearing No. 84A/13, 14 and 15,

(ii)

Cloud free digital data of IRS-1D, LISS III (Linear Imaging Self Scanner) date of pass 04th February, 2001 in three spectral bands viz. band 2 (0.52 – 0.59 μm), band 3 (0.62 – 0.68 μm) and band 4 (0.77 – 0.86 μm) with path-113 & row-055 (23.5 m spatial resolution), was procured from National Remote Sensing Centre (NRSC), Hyderabad, India and

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Shuttle Radar Topography Mission (SRTM) digital elevation data with a spatial resolution of 90 m was downloaded from the CGIAR Consortium for Spatial Information site (http;//srtm.csi.cgiar.org).

All the data were geometrically rectified and projected into UTM, WGS-1984 datum, 46N zone projection system, so that errors can be minimized in GIS platform. ERDAS Imagine - 9.2 has been used for the digital analysis of remotely sensed data and was geometrically corrected and resampled taking toposheets as reference. The drainage networks and watershed boundary were delineated and digitized from SoI topographic maps and then updated from satellite data at scale of 1:50,000. The data extraction and analysis were carried out using ArcGIS-10.2 tools.

For the determination of stream order, Strahler (1964) system was followed and the stream length had been computed as per the law of Horton (1945). The different geomorphometric parameters were computed using standard mathematical formulas of Gravelius (1914), Horton (1932 & 1945), Miller (1953), Schumm (1956), Melton (1957), Hadely and Schumm (1961), Strahler (1964), Stoddart (1965), Kumar et. al. (2000) and Sreedevi et. al. (2005).

Sediment production rate and run-off were estimated based on Jose and Das (1982) method. The drainage map of the area was prepared from SoI toposheets which were updated using IRS-1D, LISS-III imagery. Updated drainage map was used for the analysis of drainage patterns of the study area. Geological map of the area had been prepared from geological map of Mizoram worked out by Ganju (1975) and based on ground information. Flow direction and flow accumulation of the watershed have been estimated by using ArcHydro Tools in ArcGIS-10.2 software. Digital Elevation Model (DEM) was generated from SRTM 90 m resolution data using Surface Tools in ArcGIS-10.2 software.

Results and Discussions The geomorphometric parameters of the watershed have been classified into four different categories viz. drainage network, basin geometry, drainage texture and relief, which are discussed in the following sections.

1) Drainage Analysis The parameters such as stream order, stream number, stream length, mean stream length, stream length ratio, bifurcation ratio and Rho coefficient, which were described and the results have been tabulated in table 1.

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TABLE 1: STREAM HIERARCHY AND ASSOCIATED FEATURES OF THE TUIRINI WATERSHED

Stream order 1st 2nd 3rd 4th 5th 6th Total

Number of streams 2177 436 91 20 4 1 2729

Stream length Mean stream (km) length (km) 1246.75 0.57 311.73 0.71 137.62 1.51 61.27 3.06 26.68 6.67 22.24 22.24 1806.29 -

Stream length ratio 1.24 2.12 2.02 2.17 3.33 -

Bifurcation ratio 4.99 4.79 4.55 5.00 4.00 -

Mean Rho coefficient bifurcation ratio

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Regression of Logarithms of Stream Numbers, Streams Length versus Streams Order

FIG. 5A: REGRESSION OF LOGARITHMS OF STREAM NUMBERS Log (Nu) VERSUS STREAMS ORDER (u)

FIG. 5B: REGRESSION OF LOGARITHMS OF STREAM LENGTHS Log (Lu) VERSUS STREAMS ORDER (u)

The graphical relationship between the log value of stream numbers against stream orders when plotted gives a straight line (Fig.5A) and supports the Horton (1945) ‘law of stream numbers’, which state that the number of stream segments of each order usually decreased in geometric progression as the stream order increased. Similarly, the logarithm plot of streams length versus stream order showed a linear relationship with a small deviation from a straight line (Fig.5B) and confirmed to Horton (1945) ‘law of stream length’, which stated that the average length of streams of different orders in a drainage basin tended closely to approximate a direct geometric ratio. It is also evident from the fig. 5A & 5B that the linear pattern of drainage networks indicates the homogenous rock material subjected to weathering and deviation from its general behaviour suggests the lithologic and topographic variation across the watershed.

1.1) Stream Order, Number and Length Stream order expresses the hierarchical relationship between the stream segments within a drainage network and the order wise stream segment is the stream number. The length of stream segments in each order is known as stream length. There are 2729 streams sprawled over an area of 420.07 sq.km, out of which 79.78 % area is of 1st order, 15.97 % area is of 2nd order, 3.34 % area is of 3rd order, 0.73 % area is of 4th order, 0.14 % area is of 5th order and 0.03 % area is of 6th order stream. In the watershed most dominant streams are 1 st order, followed by 2nd order and then 3rd, 4th, 5th and 6th order stream (Fig. 3). 1st and 2nd order streams which are located mostly in high elevated area with steep slopes. Similarly, the length of 1st order streams constitute 69.02 %, 2nd order streams constitute 17.25 %, 3rd order streams constitute 7.61 %, 4th order streams constitute 3.39 %, 5th order streams constitute 1.47 % and 6th order stream constitute only 1.24 % of the total stream length. It is also observed that the total length of stream segments is maximum in 1st order streams and decreases as the stream order increases.

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1.2) Mean Stream Length The mean stream length (Lsm) has been calculated as the ratio of the total stream length of order ‘u’ to the number of streams of order ‘u’ (Strahler, 1964). Normally the mean stream length of a given order is higher than the next higher order. The Lsm values of the watershed ranges from 0.57 to 22.24 km. The deviation of the computed values might be due to the presence of high relief and steep slopes in the watershed.

1.3) Stream Length Ratio The stream length ratio, which is defined as the ratio of the mean length of streams of a given order (Lu) to the mean length of the streams of the next lower order (Lu-1), has important relationship with surface flow and erosional stages of the watershed (Horton, 1945). The stream length ratio between successive streams order depends on slope and topographic conditions of the watershed. The stream length ratio of the watershed varies from 1.24 to 3.33 indicates youth to mature stage of geomorphic development of streams.

1.4) Bifurcation Ratio Bifurcation ratio is related to the branching pattern of the drainage network and is calculated by dividing the total number of streams in the lower order by the number of streams of the next higher order (Schumm, 1956).

Bifurcation ratio characteristically ranges between 3.0 and 5.0 for basin in which the geologic structures do not distorted the drainage pattern (Strahler, 1964). In the study area it is noticed that the bifurcation ratio varies from 4.0 to 5.0 and mean bifurcation ratio is 4.66 indicates that there is strong structural control over the drainage development.

1.5) Rho Coefficient It is defined as the ratio of stream length ratio to the bifurcation ratio and represents relationship between drainage density and physiographic development of a watershed which evaluates the amount of water storage capacity of the watershed (Horton, 1945). Higher values of Rho coefficient indicate high capacity for the storage of water and lower values indicate low storage capacity of water in a watershed. Rho coefficient of a watershed is controlled by climate, geological structures and lithology of the area. The value of Rho coefficient for the Tuirini watershed is 0.47, which reveals that the watershed is having low water storage capacity and prone to soil erosion.

2) Geometry of Basin Shape Rate of run-off and sediment production rate is largely affected by the shape of the watershed and it controls the rate at which the water and sediments are discharged to the outlet. Basin geometry which includes form factor, circularity ratio, compactness coefficient, elipticity index and fitness ratio which are discussed below.

2.1) Form Factor It is expressed as the ratio between the watershed area to the square of the watershed length (Horton, 1932).

Higher the value of form factor is, more circular the watershed will be, whereas long narrow watershed has low form factor value, which is close to zero. The watersheds with high form factor have high peak flows for shorter duration, while the elongated watershed with low form factor have low peak flows for longer duration (Chopra et. al., 2005). The form factor value of the Tuirini watershed is 0.20 indicates more elongated in nature with flatter peak flow for longer duration.

TABLE 2: GEOMETRIC AND RELIEF ASPECTS OF THE TUIRINI WATERSHED

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Length of main stream (Ls) km

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45.30

56.75

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Max (H)

Min (h)

Source (a)

Confluence (b)

Fall in height (a-b) km

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78

780

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2.2) Circularity Ratio According to Miller (1953), circularity ratio (Rc) is the ratio of the watershed area (A) to the area of the circle whose perimeter (P) is equal to the perimeter of the watershed and this ratio can be expressed as Rc = 12.57∗A/P2. Watersheds with low value of circularity ratio are characterized by elongated shape, high relief with steep slopes and its higher value represents more circularity in shape, moderate relief with gentle slopes.

The circularity ratio of the Tuirini watershed is 0.42 indicates that the watershed is elongated in shape, high relief with steep slopes.

2.3) Compactness Coefficient According to Gravelius (1914), compactness coefficient (Cc) is the ratio of the watershed perimeter (P) to the circumference of circular area, which equals the area (A) of the watershed and mathematically, it can be expressed by Cc = 0.2821 P/ A0.5. The value of Cc indicates the rate of erosion and nature of watershed shape.

A watershed shape is a perfect circle, when Cc is equal to unity. The Cc value of the Tuirini watershed is found to be higher than unity i.e. 1.57 indicating its elongated shape.

2.4) Elipticity Index Elipticity index (Ei) is obtained by dividing the square of the watershed length (Lb) to the total area (A) of watershed (Stoddart, 1965) and calculated by the formula: Ei = 0.79 ∗ Lb2/A. The value of elipticity index varies from one to infinity and its higher value indicates more elongated shape of the watershed. The value obtained for the study area is 3.88, indicating elongated shape of the watershed.

2.5) Fitness Ratio The fitness ratio is expressed as the ratio between the main stream length (Ls) to the watershed perimeter (P), which is a measure of topographic fitness (Melton, 1957). The fitness ratio of the study area is 0.52 indicates rugged topography associated with high relief and steep slopes.

3) Drainage Texture Analysis Drainage texture aspects considered for the present study includes drainage density, stream frequency, infiltration number, texture ratio and constant of channel maintenance, which have been described below.

3.1) Drainage Density Horton (1945) defined drainage density as the total streams length of all orders in a watershed divided by the watershed area. It is influenced by climate, vegetation cover, nature of bed rock and relief of the area. According to Nag (1998) the low drainage density of a region indicates permeable subsurface material under dense vegetative cover with low relief. High drainage density is related to the areas of impermeable subsurface strata and sparse vegetation with high relief. The drainage density value of the study area is 4.35 km/sq.km, which reveals that the area is characterized by impervious rocks under sparse vegetation cover and high relief.

3.2) Stream Frequency It is expressed as the ratio between the total number of stream segments to the watershed area (Horton, 1932).

High stream frequency is characteristics of areas having low penetration capacity of the soil, high surface runoff and medium to high relief whereas low stream frequency is observed in the areas of permeable rocks and low relief. The value of stream frequency for the watershed is 6.57 per sq.km indicates high relief and low permeability of the subsurface formation.

3.3) Infiltration Number Infiltration number of a watershed is the product of drainage density and stream frequency (Horton, 1932).

Infiltration number gives an idea about the rate of absorption of water by soil and its value largely controlled by vegetation cover, lithology and soil texture of the area. Lower the value of infiltration number, higher will be the infiltration capacity and low surface runoff of the watershed will be. The value of infiltration number obtained for the Tuirini watershed is 28.57 revealing low infiltration rate and high runoff of the area.

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3.4) Texture Ratio Horton (1945) defined texture ratio as the total number of stream segments of all orders in a watershed to the perimeter of the watershed. It helps to understand the relative spacing of drainage lines. Generally, lower values of texture ratio indicate coarse to moderate textures, low drainage density, low relief and high permeability of the area whereas higher values suggests fine to ultra-fine textures, high drainage density and high relief with steep slopes. In the present study the watershed has a drainage texture of 24.65 per km, which reveals that the area is characterized by very fine texture, high drainage density and high relief with steep slopes.

3.5) Constant of Channel Maintenance Constant of channel maintenance (Cm) is defined as the area of the watershed surface needed to maintain a unit length of stream channel and is expressed by the reciprocal of drainage density (Schumm, 1956). Its value depends on climate, vegetation, relief and lithology of the area. Higher value of this parameter suggests low relief, high permeability and low drainage density with coarse drainage texture. The constant of channel maintenance value for the watershed is 0.23 sq.km/km, it means 0.23 sq.km of surface area is required to maintain each kilometre of channel length and this low value also indicates that the area is characterized by high surface runoff, low permeability and high drainage density.

Legend DEM High:1905 m

Low:78 m

FIG. 6: 3D VIEW OF THE TUIRINI WATERSHED

4) Relief Analysis The relief characteristics of the watershed viz. watershed relief, absolute relief, relative relief, dissection index, gradient ratio and time of concentration are measured for the present study and have been discussed below.

4.1) Relief and Absolute Relief The difference between the highest elevation on the ridge and lowest elevation on the valley floor is known as the relief (R) of the watershed. It has an influence on the channel slope which controls the flood pattern and the amount of sediments which get transported (Hadely and Schumm, 1961). The maximum (H) and minimum (h) elevations of the Tuirini watershed is 1905 m and 78 m respectively, thus watershed relief is 1.82 km that indicates high relief with steep slopes of the area. Absolute relief (Ar) is the highest elevation of an area above the mean sea level and the Ar of the study area is 1905 m.

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4.2) Relative Relief Relative relief (Rr) is determined as the ratio between the watershed relief (R) to the perimeter (P) of the watershed and is estimated based on Melton (1957) formula: Rr = 100 ∗ (R/P). Its lower value indicates gentle topography whereas higher value suggests steeper slopes of the terrain. The relative relief of the study area is 1.64 which represents the land surface has moderate to steep slopes.

4.3) Dissection Index Dissection index (Di) is the ratio between relief (R) to the absolute relief (Ar) of an area and gives clue to the stages of landscape evolution and degree of dissection or vertical erosion of a region (Singh and Dubey, 1994).

The values of dissection index ranges from 0 (complete absence of dissection) to 1 (vertical cliff). Di value of the study area is 0.95, indicating the mature stage of landscape development with highly dissected mountainous terrain.

4.4) Gradient Ratio It is expressed as the ratio of the difference of source elevation (a) and mouth elevation (b) of major stream of the watershed to the length of major stream (Ls) of that watershed. Gradient ratio (Gr) is calculated according to Sreedevi et. al. (2005) formula: Gr = (a‐b)/Ls. The Gr of the watershed is 0.012, which reveals the moderate gradient of the terrain.

4.5) Time of Concentration The time of concentration (Tc) is the time taken by water to travel from the farthest point of a watershed to its outlet. The highest Tc value represents the greatest length of time for water to travel from the remotest point of the watershed to its outlet (Ozdemir and Bird, 2009). It is computed based on Kumar et. al. (2000) formula: Tc = 6.95 (Ls1.15/R0.385), where Ls is the length of the major stream and R is the watershed relief. The Tc value of the watershed is high i.e. 574.0 min, which suggests that the flow discharges in longer duration of time.

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FIG. 8: FLOW ACCUMULATION IN THE TUIRINI WATERSHED

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Flow Direction and Flow Accumulation of the Tuirini Watershed Flow direction and flow accumulation are important in hydrologic modelling to determine the paths of water movement and the zones of accumulated flow of the watershed. Flow direction was calculated for each pixel from the filled DEM. The values of each pixel in the flow direction grid had a code for describing one of eight possible directions in which water will flow out of that pixel and this concept is called the eight-direction (D8) pour point model (Fairfield and Leymarie, 1991). Flow accumulation is defined as the accumulated number of cells upstream representing the upstream watershed area. It was calculated based on the flow direction grid. The flow accumulation grid records the number of cells located upstream of each cell will contribute drainage area to each cell. Fig. 7 & 8 represents the flow directions and flow accumulation of the watershed.

Estimation of Sediment Production Rate Sediment production rate is the volume of sediment produced per unit watershed area per unit time.

The sediment production rate of the watershed has been estimated based on the model suggested by Jose and Das (1982) and is expressed by the following equation: Log (SPR) = 4919.80 + 48.64 log (100 + Rf) – 1337.77 log (100 + Cr) – 1165.64 log (100 + Cc) where, SPR is sediment production rate, Rf is form factor, Cr is circulatory ratio and Cc is compactness coefficient.

From this analysis, the SPR was found to be 1.18 ha-m/100 sq.km/yr indicates that the watershed produces moderate amount of sediments annually due to undulating topography and high intensity of rainfall.

Estimation of Run-off Rate The amount of water transported through the rivers from its source to other places can be measured as a run-off.

It depends on the amounts of precipitation, evapotranspiration and percolation which in turn are affected by climatic conditions, lithology, structure, relief and other surface properties (Sinha, 1966). Generally, run-off rate is relatively high in hilly areas due to high relief with steep slopes whereas in the plain areas run-off rate is low because of low relief, gentle slope and resulting high permeability of the terrain. Run-off rate of the watershed was estimated using Jose and Das (1982) model, which expressed by the formula: Log Q = 2238.43 + 22.12 log (100 + Rf) – 608.28 log (100 + Cr) – 530.02 log (100 + Cc) where, Q is run-off of the watershed, Rf is form factor, Cr is circulatory ratio and Cc is compactness coefficient.

The total runoff value obtained for the Tuirini watershed is 2.27 cm/sq.km suggesting that the area is characterized by high discharge of runoff and low permeability due to rugged topography and high degree of slopes.

Conclusion Estimation of geomorphometric parameters, sediment production rate and run-off rate of the watershed are needed for effective planning, development and management of natural resources of an area. Remote sensing and GIS are the most advanced tools for watershed monitoring and development. Geologically, the terrain is composed of sandstones, shales and siltstones belongs to Bhuban Sub-Group of Surma Group. The study area is dominant by trellis type of drainage pattern, which indicates that the terrain is characterized by folded sedimentary strata and strong structural control upon streams. The total 2729 streams recognized in the study area sprawle over an area of 420 sq.km and the computed values of stream length ratio indicate youth to mature stage of geomorphic development of streams. The mean bifurcation ratio indicates that the drainage pattern is structurally controlled and the value of Rho coefficient reveals that the watershed is having low water storage capacity. The analysed value of shape parameters indicates elongated shape of the watershed with flatter peak flow for longer duration.

The drainage density and stream frequency value reveals that the area is characterized by impermeable rocks, sparse vegetative cover with high relief. The value of texture ratio and constant of channel maintenance of the watershed indicate very fine drainage texture and low permeability associated with high surface runoff. The computed value of relief parameters of the study area represents rugged nature of topography with high relief and steeper slopes. The watershed having the high time of concentration value indicates that longer duration of flow discharges. The estimated value of sediment production rate and run-off rate suggests that the watershed produces moderate amount of sediments annually and is characterized by high runoff zone due to high relief with steep slopes. The overall results indicate that the Tuirini watershed is prone to soil erosion associated with high rate of run-off.

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International Journal of Remote Sensing Applications (IJRSA) Volume 5, 2015

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ACKNOWLEDGEMENTS

The authors express their gratitude to Head, Department of Geology, Mizoram University for providing Remote Sensing and GIS laboratory facilities to carry out the current work. The first author is grateful to University Grants Commission (UGC), New Delhi for providing financial support for the present research work.

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