5:15 PM - 6:45 PM
[HGM03-P07] Reevaluation of Waterfall Face Shapes in "100 Famous Waterfalls in Japan" Using Hydrological and Geomorphic Information of Watershed
Keywords:waterfall, shape classification, open data, 100 Famous Waterfalls in Japan
The "100 Famous Waterfalls in Japan" selects waterfalls with historical and cultural significance through nationwide public solicitation. The guidebook summarizes the characteristics of waterfall shapes and geological features and is utilized for tourism purposes. Geomorphologically, waterfalls are referred to as knick points, where the riverbed gradient sharply increases discontinuously from upstream to downstream. Previous studies on waterfalls have examined the formation mechanisms of specific locations and the recession rate of waterfalls. However, there have been no cases where hydrological and geomorphological information from watersheds where waterfalls are formed has been comprehensively aggregated and analyzed nationally.
Furthermore, the "100 Famous Waterfalls in Japan" classification of waterfall shapes is not based on geomorphology or hydrology (Fig, 1-a). Therefore, it is necessary to clarify whether hydrological and geomorphological information that forms waterfalls influences the shape of the waterfall face. Thus, this study uses GIS to analyze hydrological and geomorphological information of watersheds containing waterfalls and classify waterfall shapes. Additionally, it seeks to compare the results of this study with the classification of waterfall shapes in the "100 Best Waterfalls in Japan" and reevaluate them from a geomorphological and hydrological perspective.
In this study, hydrological information, such as the watershed area upstream of the waterfall, annual average precipitation, and topographical information, such as elevation, average slope angle, and geological conditions, were integrated using GIS to organize the characteristics of watersheds that constitute waterfalls. The flow rate was calculated by multiplying the watershed area and the annual average precipitation. Moreover, the shapes of waterfalls selected in the "100 Famous Waterfalls in Japan" were observed through publicly available online photographs and field surveys. The shape classification was subdivided by analyzing the hydrological and geomorphological information.
Vertical waterfalls tend to have larger watershed areas and a higher proportion of igneous and volcaniclastic rocks than other shapes. Also, based on photographs and field surveys, tiered waterfalls were classified into two shapes: staircase waterfalls and tiered waterfalls with plunge pools forming at each stage. staircase waterfalls tend to have flow rates below the average, with a higher proportion of igneous and volcaniclastic rocks. Tiered waterfalls with plunge pools forming at each stage tend to have flow rates above the average, with a higher proportion of sedimentary rocks.
Furthermore, branching waterfalls were classified into two shapes: widening waterfall faces as water falls and branching waterfalls at the knickpoint. Branching waterfalls tend to have higher flow rates relative to the watershed area than other shapes and a higher proportion of igneous and volcaniclastic rocks. Among them, branching waterfalls at the knickpoint tend to have a higher average annual precipitation in the watershed than the average of widening waterfall faces as water falls. (Fig, 1-b)
This study revealed different trends in shape classification from "100 Famous Waterfalls in Japan" based on hydrological and geomorphological information. Based on the results of this study, it is necessary to survey the shapes of waterfall faces, define them, and then examine the factors causing differences in the shapes.
Furthermore, the "100 Famous Waterfalls in Japan" classification of waterfall shapes is not based on geomorphology or hydrology (Fig, 1-a). Therefore, it is necessary to clarify whether hydrological and geomorphological information that forms waterfalls influences the shape of the waterfall face. Thus, this study uses GIS to analyze hydrological and geomorphological information of watersheds containing waterfalls and classify waterfall shapes. Additionally, it seeks to compare the results of this study with the classification of waterfall shapes in the "100 Best Waterfalls in Japan" and reevaluate them from a geomorphological and hydrological perspective.
In this study, hydrological information, such as the watershed area upstream of the waterfall, annual average precipitation, and topographical information, such as elevation, average slope angle, and geological conditions, were integrated using GIS to organize the characteristics of watersheds that constitute waterfalls. The flow rate was calculated by multiplying the watershed area and the annual average precipitation. Moreover, the shapes of waterfalls selected in the "100 Famous Waterfalls in Japan" were observed through publicly available online photographs and field surveys. The shape classification was subdivided by analyzing the hydrological and geomorphological information.
Vertical waterfalls tend to have larger watershed areas and a higher proportion of igneous and volcaniclastic rocks than other shapes. Also, based on photographs and field surveys, tiered waterfalls were classified into two shapes: staircase waterfalls and tiered waterfalls with plunge pools forming at each stage. staircase waterfalls tend to have flow rates below the average, with a higher proportion of igneous and volcaniclastic rocks. Tiered waterfalls with plunge pools forming at each stage tend to have flow rates above the average, with a higher proportion of sedimentary rocks.
Furthermore, branching waterfalls were classified into two shapes: widening waterfall faces as water falls and branching waterfalls at the knickpoint. Branching waterfalls tend to have higher flow rates relative to the watershed area than other shapes and a higher proportion of igneous and volcaniclastic rocks. Among them, branching waterfalls at the knickpoint tend to have a higher average annual precipitation in the watershed than the average of widening waterfall faces as water falls. (Fig, 1-b)
This study revealed different trends in shape classification from "100 Famous Waterfalls in Japan" based on hydrological and geomorphological information. Based on the results of this study, it is necessary to survey the shapes of waterfall faces, define them, and then examine the factors causing differences in the shapes.