Morphometric analysis of watersheds in Kelani river basin for soil and water conservation

the soil erosion characteristics in river basins and is used to There is evidence of higher rates of soil erosion occurring in the Kelani river basin. Thus, soil conservation in this basin is crucial at present. Kelani Kelani river basin and observed turbidity data validated the morphometric base priority for soil and Kelani river basin. Results of the study conservation in Kelani river basin in Sri Lanka.


INTRODUCTION
The importance of morphometric analysis of a drainage basin is pivotal to understand the geological and Sarada river basin.The analysis of various linear and areal aspects have revealed that the the basin have set a dendritic to sub-dendritic drainage th order drainage.Omar (2015) conducted a morphometric analysis of the Kshipra river basin located in the Madhya Pradesh of Central India and found that the geomatic techniques are effective tools to understand and computate various terrain parameters, and for the analysis of a basin for prioritisation of soil conservation.
The Kelani river drains an area about 2,300 km 2 and of people in the greater Colombo area.Over 10,000 industries and businesses, providing a vast number of Kelani river basin.The ecosystem of the Kelani river basin supports socioeconomic activities such as agriculture, mining, urban development, industrial development, basin contains some of the most picturesque landscapes in Sri Lanka, offering a high potential to be developed as probably giving an alternative to the present industrial mass of sediments in the Kelani river has revealed that, on average about 2,300 metric tons of sediments pass

Materials
This study used digital elevation model (DEM) of Sri Lanka as the base map for the generation of morphometric parameters (Figure 1).Turbidity data collected from the National Water Supply and Drainage (ver.10.2), as an interface to derive the morphometric parameters from DEM.The linear morphometric parameters such as elongation ratio (Re), drainage density (Dd), stream frequency (Fs), foam factor (Ff) and drainage texture erodibility 1999).These parameters are also termed as erosion risk assessment parameters.Hence, the values of elongation ratio (Re), foam factor (Ff) and circularity erodibility.

Methods
et al.

Morphometric analysis of linear parameters
This study assessed linear morphometric parameters such as stream order (U), stream number (Nu), stream length (Lu), stream length ratio (RL), bifurcation ratio (Rb) and stream is an unbranched tributary; a second order stream second order tributaries.In general, an N th order stream is (Strahler, 1957 Kelani river basin.The total drainage area of the Kelani river basin is 2338.59km 2 and the the largest areal extent (298.94km 2 ).The larger basins record large Bifurcation ratio is a dimensional parameter that expresses the ratio of the number of streams of any given order (Nu) to the number of streams in the next the drainage pattern has not been distorted by structural in the Kelani structural disturbance (Table 4).frequency (Fs) is the total number of stream segments of all orders per unit area (Horton, 1932) Circularity ratio (Rc) is the circumference of a circle of (Miller, 1953).The circularity ratio is used as a quantitative measure for visualising the shape of the basin (Christopher et al frequency of streams, geological structures, land use/ land cover, climate, relief and slope of the basin.Higher values of Rc indicate that the area is characterised by high relief, elongated and permeable surface resulting basin lag times.Rc of the Kelani river basin varies from area to the square of basin length (Horton, 1932).For a less than 0.7854.The Ff for all basins vary from 0.05 to the erodibility of soil.The values of Ff for the Kelani (Nautiyal, 1994).
It is used to express the relationship of a hydrologic ).These values can be grouped into three categories as elongated in nature (Table 5).

Prioritisation based on compound value (Cp)
by assigning the highest rank based on the highest values of shape parameters.Subsequently, ranking values of all

Prioritisation based on hypsometric integral (HI)
The hypsometric integral is the area beneath the the cumulative percentage of area (Singh et al., 2008).
of the hypsometric curve indicates the age of the catchment.Hypsometric integrals and curves can be interpreted in terms of the degree of basin dissection integrals are typical for youthful stage, undissected landscapes; smooth, s-shaped curves crossing the centre of the diagram characterise mature (equilibrium typify old and deeply dissected landscapes (Strahler, 1952).If the resulted HI value is greater than or equal or at young stage indicating the susceptibility of the 0.6 it indicates a naturedly dissected (mature) landform.If the resulted value is equal or less than 0.35 it indicates (Strahler, 1952;Sarangi et al., 2001).Based on these Kelani river basin    for the entire Kelani river basin is constrained by the availability of resources.In addition, assessment of in-situ soil erosion is also a time taking activity and needs more resources.Therefore, the ranking of critical soil erosion prone areas by morphometric analysis is Kelani river basin.

CONCLUSION
Watershed prioritisation is considered as one of the most important aspects of planning and development prioritisation on the basis of compound value revealed most susceptible for soil erosion in the Kelani river basin.

Kelani river basin.
Morphometric analysis can be used to prioritise sub Kelani and observed turbidity data.The study demonstrates the utility of morphometric analysis in prioritisation decision makers for planning a river basin management plan for the Kelani river basin.

(
Panhalkar et al. morphometric parameters is of immense utility in river Hassan, 2012).Morphometric analysis could be used for the availability of soil maps (Sidhu et al et al techniques are currently being used for assessing various terrain and morphometric parameters of the basin as they et al. (2006) repo in the Victoria catchment for soil conservation using September 2017 Journal of the National Science Foundation of Sri Lanka 45(3) slope, soil erodibility and rainfall erosivity factors.These soil conservation planning in the Victoria catchment.Kothmala oya and apply proper catchment management practices using catchment characteristics derived et al. of land reclamation and soil erosion prevention in the Tulasi conservation in Biswa and Kedar sub basins of the Purna et al., 2014).Moreover, Nooka et al. (2013) used remote central hills of Sri Lanka and drains via et al., 2005).The minimum and maximum elevations in the basin range from 0 to 2345 m above mean sea level (Figure 1).receives an average annual rainfall of about 2400 mm 3 /s during the monsoon season to the Indian Ocean (De Silva et al., 2012).Main agricultural land uses in the area are tea, rubber, grass and forest in the upper catchment and the separately calculated as an individual entity to evaluate 8 values (D-8 method).It represents the direction, in , accumulation operation performs a cumulative count of the number of pixels that naturally drains into outlets and Kelani the guidelines provided by the Survey Department of to the Strahler (1964) method.The stream lengths and Table 1 indicates the morphometric parameters used in references.Singh et al of hypsometric analysis (area-elevation analysis) for conservation.Hence, this study used hypsometric integral (HI) as a separate parameter in prioritisation Kelani river basin.

Figure 1 :
Figure 1: Location of Kelani river basin in Sri Lanka and variation

Kelani
river basin.the same units.The Re generally varies from 0.6 to 1.0 (Javed et al., 2009).Values close to 1.0 are typical of et al., 2013

Figure 4 :
Figure 4: Kelani river basin based on compound value

Figure 5 :
Figure 5: Kelani river basin based on the hypsometric integral

Table 1 :
Morphometric parameters, their formulas and relevant references

Table 2 :
Turbidity recording stations and periods of records et al. (2001).For validation of the results of the study,

Table 3 :
). order, higher the number of streams is implied throughout the catchment.arecharacterisedbystreams of relatively smaller lengths.Flatter gradients are generally represented by longer Kelani orders of the entire Kelani river basin.Stream length of length and that of the 8 th total stream length of 8 th order (73.13 km) is more than the length of 7 th order(38.78km).This change may occur slopes.Table3indicates the stream numbers in different river basin in Sri Lanka Figure 3: Stream order of Kelani river basin September 2017 Journal of the National Science Foundation of Sri Lanka 45(3) as the stream order increases (Manjare et al., 2014).

Table 4 :
Variation of linear parameters [area, perimeter, mean bifurcation ratio (Rb), drainage texture (Dt), drainage density (Dd) and stream frequency (Fs)] of different sub Kelani river basin September 2017 Journal of the National Science Foundation of Sri Lanka 45(3)

Table 6 :
Variation of areal [mean bifurcation ratio (Rb), drainage texture (Dt), drainage density (Dd), stream frequency (Fs)], linear [ elongation ratio (Re)], relief parameters and compound values for A, B, C, D, E sub basins and the entire basin F

Validation of the results with observed turbidity data
Researchers such as Altaf et al. (2014) and Chen et al.
turbidity Soil erosion may be enhanced further in the future in a more vigorous hydrological cycle (Amore et al., 2004, Pandey et al., 2006).A similar situation could arise in the very important Kelani