IAHR, founded in 1935, is a worldwide independent member-based organisation of engineers and water specialists working in fields related to the hydro-environmental sciences and their practical application. Activities range from river and maritime hydraulics to water resources development and eco-hydraulics, through to ice engineering, hydroinformatics, and hydraulic machinery.
Log On
About IAHRDirectoryCommitteesMy IAHRNews & JournalseLibraryeShopEventsJoin IAHRWorld CongressDonate
spacer.gif
spacer.gif eLibrary
spacer.gif eLibrary
You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Extreme events, natural variability and climate change : Risk assessment of sediment disaster based on watershed-wide hydrologic processes
Risk assessment of sediment disaster based on watershed-wide hydrologic processes
Author : MAKOTO NAKATSUGAWA(1), TOMOHIDE USUTANI(2) & TAKAYUKI MIYAZAKI(3)
ABSTRACT
This study addresses risk assessment for sediment disasters based on watershed-wide estimations of soil moisture
resulting from long-term hydrologic processes. Sediment disasters have recently occurred throughout Japan due to
heavy rainfall and rapid snowmelt. Climate change is expected to exacerbate such disasters in snowy regions, due to
global warming.
Quantitative evaluation for risk of landslides such as those that have occurred at Nakayama Pass in Sapporo, Northern
Japan, during the snowmelt season has remained an issue. A method for determining the soil moisture at potential
sediment disaster sites was proposed and applied to the Nakayama Pass disaster. This site is in the Hoheikyo Dam
watershed and thus is influenced by its hydrologic characteristics.
We propose methods to quantitatively estimate soil moisture, which is an important factor in sediment disasters, by
using the Soil Water Index (SWI) and Water Storage (WS) estimated as THE water level of the tank model when rainfall
and snowmelt are given. Model parameters of the SWI are uniform in all Japan. In contrast, parameters of WS can be
changed in depending on watershed characteristics. WS in each 1-km by 1-km mesh is estimated as the water level of
the tank model when rainfall and snowmelt are given. Then, the total outflow from the watershed is estimated by
synthesizing the outflow for each mesh using a channel-routing method based on kinematic waves. The validity of the
estimated WS is indirectly confirmed by the reproducibility of total outflow from the dam catchment that includes the
disaster point.
Amounts of SWI and WS at the disaster site were estimated, and then it was found that the landslides of 2012 and 2000
had occurred under the condition of maximum SWI or maximum WS resulting from heavy rainfall, combined with
snowmelt. SWI had slightly underestimated the risk. Thus, this study suggested that the amount of WS based on
hydrologic cycle in a catchment area influences large-scale slope disasters such as landslides. It is believed that the risk
of slope disasters resulting from high soil moisture content can be predicted by incorporating appropriate weather data
into the distributed hydrologic model, which is a model that can consider rainfall as well as snowmelt.
File Size : 1,836,590 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Extreme events, natural variability and climate change
Date Published : 18/08/2015
Download Now