The Influences of Urbanization and Land Use Transformation to Hydro-ecology A Case Study of Nakhon Si Thammarat Province Urban Area

Abstract

The city of Nakhon Si Thammarat is an ancient community that developed on the flat land along the eastern side of the Luang Mountain Range in Nakhon Si Thammarat Province, since around the 12th century of the Buddhist era. The transformation of land use in the form of an urban community, which is a human-made landscape designed to be suitable for living in each era, has led to changes in the area's hydrological system, particularly in the volume of water flow and the increased rate of water flow within the area. Additionally, the water retention capacity of the land has decreased due to the increased areas of impervious surfaces.

This research thus aims to study the impacts on the hydrological ecosystem in the case study of Nakhon Si Thammarat City, caused by changes in land use and urban expansion. The study involves creating a map of the city's expansion by analyzing satellite imagery, historical records related to the city, and development plans to identify periods of urban growth. Additionally, the study examines the local hydrological system by collecting data on current water sources, rainfall amounts, and flood-prone areas to explain the characteristics of urban expansion and its effects on the hydrological ecosystem.

By studying the city's expansion using historical city plans and extensions from the years 1077 and 1686, and overlaying them onto the current study area, it was found that the urban area was confined to the sandy ridge or what is now Ratchadamnoen Road. Additionally, the construction of a city moat was found, designed to protect and assist with water drainage during the flood season. When compared with the city's expansion today, satellite images from 1994 to 2024 were analyzed by converting the Normalized Difference Vegetation Index (NDVI) to separate the urban area from green spaces. This revealed that the city expanded beyond the sandy ridge, unlike earlier periods, due to the development of land transportation systems. When combining data on the city's expansion with flood zone information, it was found that during the 24th century of the Buddhist era, the city's expansion extended into low-lying flood-prone areas, with some land raised to street level. This has resulted in the city's lower areas being increasingly affected by rising water volumes during flood seasons.