Research Trends and Results

Development of the technology to measure sedimenttransportation on mountainous river
HAYASHI Shin-Ichiro, Researcher
UCHIDA Taro, Senior Researcher (Ph. D of Agriculture)
OKAMOTO Atsushi, Head
Research Center for Disaster Management , SABO (Erosion and Sediment Control) Division（Key words） hydrologic and sediment measurements, suspended load, bedload

1.

Introduction
As the mountainous rivers have remarkable fluctuation
regarding the flow rate and river bed spatiotemporally,
implementation of continuous hydrologic and sedimentmeasurements (water level, suspended load and bedloadetc.) have been tentative in limited area due to various
difficulties such as damage and loss of the observation
instruments. SABO Division has been conducting thetechnological development on the hydrologic andsediment measurements. Moreover nationwide MLIT
SABO offices implement the hydrologic and sedimentmeasurements in recent years. In the revised part forinvestigation of Technical Criteria for River Works, thehydrologic and sediment measurements are stipulated toimplement and edit the results as chronological table.
2. Manual on hydrologic and sediment measurements on
the mountainous river
SABO Division has released the Technical note ofNILIM No.686 “Manual on hydrologic and sedimentmeasurements on mountainous river”. It describes thepurpose, concept and standard methods of hydrologic andsediment measurements based on the research results
such as the Project research “Research on the method forgeneral sediment management for national landconservation” (fiscal year 2008 to 2010) and themeasurements of MLIT SABO offices. Four significant
purposes of hydrologic and sediment measurements areshown in the manual as follows.
(1) Monitoring sediment transportation
Establish the future monitoring method to detect theoccurrence of the sediment production and urgency of thesediment disaster by using real time monitoring data
(2) Establishing SABO master plan and evaluation ofSABO works
Establishing SABO master plan and setting parametersof runoff analysis and numerical simulation for river bed
deformation based on the monitoring data
(3) Disaster management for landslide dams
Setting parameters of runoff analysis to predict the timingof overflow at landslide dam(4) Establishing the general sediment management plan
Estimation for sediment volume and particle size frommountainous area to downstream
Moreover the manual shows the standard methods ofthe hydrologic and sediment measurements as follows.
(1) Hydrologic measurements: precipitation, flow rate (bymeasuring water level and flow velocity)(2) Suspended load observation: Turbidity meter,
extraction of suspended load from flow directly(3) Bedload observation: Acoustic bed load meter
3. The example of analyzing the data of hydrologic andsediment measurements
Figure shows the analysis example of the comparison
between the bedload volume obtained by the acoustic
bedload meter, per catchment area and total periodical
precipitation and the volume of sediment discharge
estimated by the survey data of sedimentation in checkdam which has almost same catchment area of former
measurement, per catchment area and total periodical
precipitation. Both volumes are approximately same.
This result suggests the capability of the acoustic bedload
meter which is able to estimate the bed load volume
favorably.

Research Trends and Results

Fig. The analysis example of the relation between thevolume obtained by the acoustic bedload meterand the volume estimated by the survey data of
sedimentation in check dam
4. Future plan
We continue to gather and analyze the data ofhydrologic and sediment measurements to clarify
the factors which control sediment transportationthat varies depending on the place and flood. Then
we conduct the study to clarify to the conditions (e.g.
topography, sediment production in upstream)
which control the factors.
【Reference】

The Technical note of NILIM No.686 “Manual onhydrologic and sediment measurements on mountainous
river”
http://www.nilim.go.jp/lab/bcg/siryou/tnn/tnn0686.htm