Abstract The rapid expansion of urban areas has significantly altered hydrological dynamics, leading to increased runoff and elevated flood risks, especially during the southwest monsoon season. This study investigates the hydrological effects of urbanization over a 36-year period (1988–2023) in the Manimala subbasin, a major water contributor to the flood-prone region, Kuttanad in India. Remote sensing and hydrological analyses for 1988 and 2023 were used to assess long-term changes, with data from 2001 and 2014 incorporated to capture land use dynamics. Hydrologic analysis was conducted using Hydrologic Engineering Center—Hydrologic Modelling System (HEC-HMS) with 70 years of rainfall data, including runoff calculations based on 3-year and 5-year return periods. The result shows a 356.43% increase in built-up land within the Manimala subbasin. Land use and Land cover (LULC) change assessment indicates that evergreen forests help to reduce Land Surface Temperature (LST) compared to other land uses, whereas bareland and built-up land exacerbate it. The study further verified long-term Normalized Difference Built-Up Index (NDBI) values to assess the extent of built-up expansion and Normalized Difference Vegetation Index (NDVI) to identify the density of vegetation. The correlations between LST with NDBI and NDVI revealed a direct relationship with NDBI and an inverse relationship with NDVI. Hydrologic analysis for the period 1988–2023 showed a rise in discharge in 2023 of about 3.62% and 1.25% for the two Antecedent Moisture Conditions AMCs (AMC II and AMC III) during the 3-year return period and 0.27% and 0.07% rise during 5-year return period, respectively. The results were validated with the observed discharge data from the Manimala river station. The coefficient of determination (R2) and Nash–Sutcliffe efficiency (NSE) was found to be within the limit. Moreover, this study presents a novel strategy for the Manimala subbasin by integrating satellite-derived indices with long-term hydrological modelling to analyse how land use changes affect the downstream deltaic region, Kuttanad. It provides critical findings on how upstream urbanization influences flood severity, contributing to sustainable flood risk management planning in Kuttanad. Highlights <UnorderedList Mark="Bullet"> <ItemContent> A significant increase in built-up land has been observed in Manimala subbasin from 1988 to 2023. </ItemContent> <ItemContent> The expansion of built-up land and reduction in vegetation cover have been validated through Normalized Difference Built-up Index (NDBI) and Normalized Difference Vegetation Index (NDVI) analysis. </ItemContent> <ItemContent> Analysis of Land Surface Temperature (LST) shows that water bodies and agricultural land have lower LST compared to bareland and built-up regions. </ItemContent> <ItemContent> Hydrological analysis shows that the growth in built-up land has led to a noticeable surge in runoff volume and discharge at the Manimala subbasin from 1988 to 2023. </ItemContent> </UnorderedList>

Long-Term Influence of Land Use Patterns on Surface Characteristics and Hydrological Behavior in the Manimala Subbasin and its Impact on the Low-Lying Delta, Kuttanad, India

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发表日期：

2026年6月18日

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Neethu Lukose,
N. Sunilkumar

摘要

Abstract

The rapid expansion of urban areas has significantly altered hydrological dynamics, leading to increased runoff and elevated flood risks, especially during the southwest monsoon season. This study investigates the hydrological effects of urbanization over a 36-year period (1988–2023) in the Manimala subbasin, a major water contributor to the flood-prone region, Kuttanad in India. Remote sensing and hydrological analyses for 1988 and 2023 were used to assess long-term changes, with data from 2001 and 2014 incorporated to capture land use dynamics. Hydrologic analysis was conducted using Hydrologic Engineering Center—Hydrologic Modelling System (HEC-HMS) with 70 years of rainfall data, including runoff calculations based on 3-year and 5-year return periods. The result shows a 356.43% increase in built-up land within the Manimala subbasin. Land use and Land cover (LULC) change assessment indicates that evergreen forests help to reduce Land Surface Temperature (LST) compared to other land uses, whereas bareland and built-up land exacerbate it. The study further verified long-term Normalized Difference Built-Up Index (NDBI) values to assess the extent of built-up expansion and Normalized Difference Vegetation Index (NDVI) to identify the density of vegetation. The correlations between LST with NDBI and NDVI revealed a direct relationship with NDBI and an inverse relationship with NDVI. Hydrologic analysis for the period 1988–2023 showed a rise in discharge in 2023 of about 3.62% and 1.25% for the two Antecedent Moisture Conditions AMCs (AMC II and AMC III) during the 3-year return period and 0.27% and 0.07% rise during 5-year return period, respectively. The results were validated with the observed discharge data from the Manimala river station. The coefficient of determination (R²) and Nash–Sutcliffe efficiency (NSE) was found to be within the limit. Moreover, this study presents a novel strategy for the Manimala subbasin by integrating satellite-derived indices with long-term hydrological modelling to analyse how land use changes affect the downstream deltaic region, Kuttanad. It provides critical findings on how upstream urbanization influences flood severity, contributing to sustainable flood risk management planning in Kuttanad.

Highlights

A significant increase in built-up land has been observed in Manimala subbasin from 1988 to 2023.

The expansion of built-up land and reduction in vegetation cover have been validated through Normalized Difference Built-up Index (NDBI) and Normalized Difference Vegetation Index (NDVI) analysis.

Analysis of Land Surface Temperature (LST) shows that water bodies and agricultural land have lower LST compared to bareland and built-up regions.

Hydrological analysis shows that the growth in built-up land has led to a noticeable surge in runoff volume and discharge at the Manimala subbasin from 1988 to 2023.