Research Activities
Forest Hydrology:
Erosion Control:
The evaluation of the functions of
forest on the hydrologic cycle and gas exchange processes
Forest influences on the hydrologic and carbon cycles, regulating
the conversion of precipitation to runoff, CO2 fixation, and
evapotranspiration. The roles of forest are physically investigated
in our laboratory. Especially, in light of the current direction
of research, studies are needed today to evaluate the functions
of forest on gas exchange processes. They influence on the hydrologic
cycle on the ground surface, the conversion
of incoming solar radiation into sensible, latent and radiant
11eat losses, the production and biomass of vegetation, the weather,
and even on the global scale climatic and environmental changes.
We are quantitatively evaluating the functions of forest on the
carbon cycle as well as the hydrologic cycle, observing CO2 and
H20 exchange of various forests both at the canopy scale (eddy
correlation method using ultrasonic anemometers and infrared
gas analyzers) and at the leaf scale (direct method using porometers).
The preliminary experiments of GEWEX/GAME (Global Energy and
Water cycle Experiment/ Gewex Asian Monsoon Experiment) under
WCRP have been started since 1996. Our laboratory have taken
part in field observation at the paddy field site in Thailand
within the tropical monsoon region and the forest field site
in Siberia within the cold region.
The evaluation of the forest environment
on the hydrological and hydrochemical process in catchment
Forest eco-geosystem gives various influences on the characteristics
of chemistry at various hydrologic Processes.
To quantitatively evaluate the influences of heterogeneity in
soil moisture characteristics on discharge process of headwater
catchment, we have been operating various field observation at
hill-slopes. We are also developing physically-based numerical
models for better understanding on infiltration and preferential
flow
processes in hill-slope system.
One of the most important hydrochemical system exists in the
unsaturated / saturated infiltration process on soil profile.
The hydrochemical processes in soil are influenced by two factors
which are mutually linked; the biochemical factors which is originated
by forest ecosystem and geochemical factors Such as weathering.
The challenge is to describe and understand the inner mechanism
of hydrochemical processes in forest catchment and to find quantitative
solutions for water quality issues such as the acid rain problem.
Control of desertification in arid
and semi-arid region
Control of desertification in arid and semi-arid region is
one of the global issues for environmental conservation. Although
afforestation activities in various arid regions are socially
accepted, the intensive afforestation witt10ut appropriate plan
may lead to the serious deficit of water resources. Focusing
the arid and semi-arid regions in Northern China, the basic research
to establish a rational afforestation plan is conducted. They
include the development of land use monitoring system by remote
sensing technique and the quantitative evaluation of water budget
by processing atmospheric data.
Mechanism of sediment movement
Basic research has been carried out on debris flow, flash
mood, and shallow landslide. The relationship between shallow
landslide and underground pipe now is studied particularly. Gully
erosion and debris Rows in Mt.Fugen-Dake have been analyzed.
Remote-sensing, the numerical simulating methods arid field observation
were used for the research.
Countermeasures to prevent or reduce
sediment disasters and the Sabo-planning being compatible with
environmental concerns
More effective permeable dams are experimentally investigated
in order to store the excessive sediment and, at the same time,
not to damage the eco-system established in the streams. Sabo
countermeasures must be harmonized with natural landscape planning,
and the method is developed to present 3-dimensional figures
of sabo-planning using tile auto-3D system.
Forest influence on the hydrologic
cycle
Elements controlling hydrologic cycle in forest are studied.
Evapo-transpiration is one of the major factors. Models to interpret
the phenomena are built.
River bed erosion by meandering streams
One of the typical features of rivers in mountain regions
is the formation of meandering streams. In this study, the processes
of development of meandering streams on flat beds are investigated
experimentally. Then, a method for calculating the formation
process of meandering streams from a sand bar pattern is developed
using a 2-dimensional numerical method.
Environment of mountain rivers
Pools in mountain rivers play an important role as habitat
for fish. The geometrical and hydraulic features of pools are
investigated and the situation of habitat of fish is observed.
The formation process of pools is investigated theoretically
and observationally with a focus on step-pool system in mountain
rivers.