Analyzing the significance of morphometric parameters in runoff efficiency: a case study in Valakkayi Tode tropical watershed, Valapattanam River, Kerala, India

The areal, linear, and relief dimensions of a drainage system make up its hydrological structure. Hence, the dynamics of hydrology in a watershed is relied highly on its morphometric characteristics. They control and regulate the majority of the water movements in the system. This water movement also includes runoff which is an indispensable element of the hydrological cycle. However, while measuring runoff of a region, the morphometry characters are often ignored. The present study is focusing on identifying the role of morphometric parameters in controlling the runoff efficiency of a watershed. For that, a case study has been conducted in a tropical watershed "Valakkayi Tode" of the Valapattanam River of Kerala, South India, where the hydrology is highly active. The runoff efficiency and the morphometric influence in the watershed were examined in three steps. Primarily, the study estimated the runoff potential of sub-watersheds based on its morphometric characters. Later, soil conservation service (SCS) method based on curve number (CN) was applied to estimate direct runoff. Finally, the relationship between two outcomes were compared. The result showed that the morphometric character and runoff potentiality are highly related. However, the correlation between the outcomes of SCS method and morphometric influence of the region showed a lower value. This indicates that the outcome of SCS method is not addressing the role of morphometry of the region. Therefore, it is recommended that in any type of flow analysis, separate consideration be given to morphometric characteristics before reaching a conclusion.