Research Trends and Results

Development of the Estimation Method of theSediment Transport using the Chemical Composition
OKADA Tomonari, Head (Ph. D., Engineering)
Coastal, Marine and Disaster Prevention Department, Marine Environment Division（Key words）

Environment, Earth and sand management, Sediment, Sediment transport, Chemicalcomposition, Inner bay
1. Introduction
In the port and harbor, we have to manage the earth andsand sediments and sediment transport appropriately on
the view point of not only the maintenance of the basic
functions of the port such as to ensure the sea route but
also the environmental interest such as the cause of watercontamination and basis of the inhabitation of living
substances.
If we view it from the environment, microscopic
particles are likely to catch organic substances andharmful chemical substances and the accumulation ofsuch particles are making the sediment worse. Therefore
it is important to grasp the transport of the microscopic
particles for actions to improve the sediment. Now that it
is currently remarked that radioactive substances adhered
to microscopic particles are also moving into the marine
area from the land and accumulating, it is increasingly
important to grasp the transport of the microscopic
particles to improve the sediment. On the other hand, finesand and sand have functions as good basis for theinhabitation of living substances. It is imperative to grasp
the moving route of the fine sand and sand so as not toaccidentally block such routes by various works andaffect the existing habitats.
Therefore, in this research we have developed a method
to use chemical composition of the sediment as a new
method to estimate the transport of the sediment.
2. Method
We have implemented an analysis using sediments
collected from many points in the Tokyo bay. We haveused a Wave Length-dispersive X-Ray Spectroscopy1).
As this system is applicable to measure from lightelements (F) to heavy elements (U) on the Periodic Table,
this time we have used the values of Al, Fe, K, Mg and Si.
The analysis was implemented on classifying eachsample into the silt fraction under 63 m and sand over
63 m as we have considered the adhesive capability of
the chemical substances and difference in transportcharacteristics caused by the current.
3. Result
All of the collection points of sediments were classified
into five groups as for the silt fractions through the cluster
analysis (Fig.). Chemical composition of the silt fractions
moved in from the Sumidagawa River, Arakawa Riverand Edogawa River have belonged to the same group ■.
Based on the distribution range of the points of ■, wehave estimated that the silt fractions moved in from theSumida River Arakawa Edogawa
RiverRIver

g5
35.65

Keihin-Unga(Tokyo)

東京港

35.6
Heiwajima
35.55

35.5

Tamagawa
RiverEbitorigawa River

Keihin-Unga(Kanagawa)Tokyo Bay

Tama-Unga
35.45

35.4

35.35

35.3
139.65139.7

139.75139.8 139.85 139.9

139.95140140.05

140.1

Fig. Grouping through the cluster analysis against thechemical composition of the silt fractionSumidagawa River, Arakawa River and Edogawa River
were giving strong effects within the Port of Tokyo andover Heiwajima of the Keihin-Unga (Tokyo side). Siltfractions ■ that moved in from the Tamagawa River wereestimated to have strong effects river mouth of theTamagawa River as far as Heiwajima throughEbitorikawa River northward and as far as Daishi-Ungathrough Tama-Unga southward. The strong effects on thearea offshore of the were not clear. Although we havebeen predicting that there must be difference between themouth side and head side of the Tokyo bay, they bothbelonged to the group of the same chemical composition■.
4. Conclusion
We have shown the possibility of using the chemicalcomposition as a new index to estimate the effect range
and transport routes of the sediments of different origins.
We are further studying the crystal construction as anadditional index. This is to segmentalize the elements
evaluated as same group based on the chemicalcomposition. Those methods are expected to become
useful methods to grasp the sediment transport andimplement appropriate management of the earth andsand.
【Reference】
1) OKADA Tomonari et al (two)（2009）, Estimation of thespacial distribution of sediment using chemical compositionand particle-size distribution, Annual Journal of Coastal
Engineering，56，976-980．