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Rocky mudflow often occurs in the mountainous regions in our country by heavy rains, but manyproblems on mudflow have remained unsettled, for an example, the process of starting and stoppingof mudflow.Recently airphotographs of damaged district by mudilow have been taken for protection plann-ing.By the use of these photos starting and stopping point of mudflow can be found and the runoutextent of rocky mudflow can be estimated.Utilized airphotos are white and black pictures and the scale of photos are 1/6000, 1/8000 and1/10000.From airphotos of damaged districts at Amakusa. In Kumamoto, at Tsubeta in Niigata, Kumano and Owase city in Mie, starting and stopping points of mudflow were plotted on top-ographic maps.At the same time, flowing path of mudflow was devided into two parts, in the valley and fan.The starting point of mudflow was decided as a place where side erosion was cleary recognizedand stopping point was decided as a point where large stones stopped collectively.Runout distance of rocky mudflow estimated from above mentioned method ha-I no directrelation with the altitude of starting point, but there exists a relation between valley length andrunout distance at fan as shown in Fig. 6.And empirically the runout distance from fan head to stopping place seems to be 40% -60%of flowing down distance along valley.

金沢大学環日本海域環境研究センター, ガリーの発達過程を幾何学的形態の変化として把握することを目的として,本稿においてはガリーの有する幅,間隔,あるいはその数の統計的法則性とその水理学的発生条件を検討した.その結果ガリーは各々の斜面において特有な幅,あるいは特定の間隔に集中することが解った.また,これらのことからガリーの本数も,一つの斜面においてその幅に比例する傾向があることが解った.次に,ガリーの水理学的発生条件として新たに導入したSoil Factor (ƒ1/3/Kただしƒ;表面流出率, K; 固結度)なる物理定数が対象とする斜面の侵食性を示すものとして有効であることが解った.

近年, 山間地域における岩石の風化程度の調査, あるいは小流域からの流出機構の研究に対して, 渓流の水質の分布や変動を分析する方法が有効な手段として用いられるようになってきた1)。しかしながらこのような対象地域はおおむね歩行さえ困難な場合が多く・特にひんぱんな採水が要求される強雨時, またはその直後には巡回歩行して採水することは不可能に近い。したがってこのような障害を除くために, 山間地域において運搬が容易で手軽に備え付けの出来る自動採水器の開発を進めることは・山間地域の災害研究にとって重要な意義があると考えられる。もとより小型の簡易採水器に万全の機能を要求することは困難なことであるが, 少なくとも一定時間間隔で数日にわたって採水を続け・一度採水した水の特性を保持するという条件は満たさねばならない。このような意図にそって簡易採水器を設計試作した。, It is well known that the chemical composition of runoff water is closely related tothe spieces of basal rock and the degree of its weathering in a mountain region, and thatthe correlation between the chemical constituents offers a valuable clue in the considera-tion of runoff process. For such investigation, it is necessary to carry out the samplingof stream water periodically even under a stormy weather, and an automatic watersampler which can be set easily beside any stream was deviced in our laboratory.This sampler takes in a stream water through an intake pipe and pours the water intowater containers arranged in a circle through the delivering pipe which is rotated with aclock at constant angular velocity.Special cares are taken to reduce the contact of stored water with air in order toprevent a change in chemical character of sampled water.

資料番号: SA0125517000

A new observation system for rocky mudflow was designed by the Mudflow Research Group.The system consists of a detector on mudliow arrival and automatic switch circuit for VTR, 35mmcamera and firing of flare tube in order to record the state of moving mudflow. In addition to thissystem, rain gauges and water level recorder are necessary for the survey of hydrological characterin a small mountaineous basin. During last summer in 1970, the observation system and hydrolo-gical survey instruments had been set along Kamikamihori valley at eastern slope of Mt. Yake andtested in regard to the practical effectiveness. The front velocity (1-5 m/see) of mudflow wasmeasured correctly from the record obtained by the new system.

Airphoto analysis and field surveys were carried out for the study of geomorphologicalcharacter of landslides resulting from heavy rains at Rokko mountain system and Tsubetadistricts in 1967.The relations between the number of landslides, the number of stream segments andthe mean relief at specified areas were investigated with reference to geological condi-tions at Rokko mountain system.Boulder distributions after mud flows at Tsubeta and Horikoshi valleys were observedby the use of radio controlled airplane and it was found that large boulders were distri-buted almost uniformly over the lower valleys and alluvium fans.

It is very important for us to clarify the physical processes of rocky mudflow which have been causing serious damages in many mountainous regions of Japan. In order to carry out a systematic and practical observation on moving state of a rocky mudflow, we contrived a new observation system, and set it along valleys on the eastern slope of Mt. Yake in the North Japan Alps. This system consists of two parts. The one is an automatic measurement system which can record frontal velocity, dynamical impact force, visual state of a rocky mudflow and discharge. The other is a combination of various observation instruments and contains rain gauges, ground water level gauges, pressure mark gauges and cylinders to sample the mud from a mudflow head. During the past four years, we have succeeded six times in observing rocky mudflows. Important results obtained from these observations are reported in this paper. They are the variation of the frontal velocity along the valley, the magnitude of impact force, and the relation between the occurrence of mudflow and precipitation.

Airphoto analysis and field surveys were carried out for the study of geomorphologicalcharacter of landslides resulting from heavy rains at Rokko mountain system and Tsubetadistricts in 1967.The relations between the number of landslides, the number of stream segments andthe mean relief at specified areas were investigated with reference to geological condi-tions at Rokko mountain system.Boulder distributions after mud flows at Tsubeta and Horikoshi valleys were observedby the use of radio controlled airplane and it was found that large boulders were distri-buted almost uniformly over the lower valleys and alluvium fans.

Rocky mudflow often occurs in the mountainous regions in our country by heavy rains, but manyproblems on mudflow have remained unsettled, for an example, the process of starting and stoppingof mudflow.Recently airphotographs of damaged district by mudilow have been taken for protection plann-ing.By the use of these photos starting and stopping point of mudflow can be found and the runoutextent of rocky mudflow can be estimated.Utilized airphotos are white and black pictures and the scale of photos are 1/6000, 1/8000 and1/10000.From airphotos of damaged districts at Amakusa. In Kumamoto, at Tsubeta in Niigata, Kumano and Owase city in Mie, starting and stopping points of mudflow were plotted on top-ographic maps.At the same time, flowing path of mudflow was devided into two parts, in the valley and fan.The starting point of mudflow was decided as a place where side erosion was cleary recognizedand stopping point was decided as a point where large stones stopped collectively.Runout distance of rocky mudflow estimated from above mentioned method ha-I no directrelation with the altitude of starting point, but there exists a relation between valley length andrunout distance at fan as shown in Fig. 6.And empirically the runout distance from fan head to stopping place seems to be 40% -60%of flowing down distance along valley.

It is well known that the chemical composition of runoff water is closely related tothe spieces of basal rock and the degree of its weathering in a mountain region, and thatthe correlation between the chemical constituents offers a valuable clue in the considera-tion of runoff process. For such investigation, it is necessary to carry out the samplingof stream water periodically even under a stormy weather, and an automatic watersampler which can be set easily beside any stream was deviced in our laboratory.This sampler takes in a stream water through an intake pipe and pours the water intowater containers arranged in a circle through the delivering pipe which is rotated with aclock at constant angular velocity.Special cares are taken to reduce the contact of stored water with air in order toprevent a change in chemical character of sampled water.

A new observation system for rocky mudflow was designed by the Mudflow Research Group.The system consists of a detector on mudliow arrival and automatic switch circuit for VTR, 35mmcamera and firing of flare tube in order to record the state of moving mudflow. In addition to thissystem, rain gauges and water level recorder are necessary for the survey of hydrological characterin a small mountaineous basin. During last summer in 1970, the observation system and hydrolo-gical survey instruments had been set along Kamikamihori valley at eastern slope of Mt. Yake andtested in regard to the practical effectiveness. The front velocity (1-5 m/see) of mudflow wasmeasured correctly from the record obtained by the new system.