Possible Scenarios for Rjecina River Catchment -on the Example of Grohovo Landslide

Abstract

リエカ市に河口をもつリエチナ川はクロアチアの典型的な海岸カルスト地域を流れ、急流な河道をもつ代表的な河川である。河道の流域中央部は渓谷の最も不安定な箇所で地滑り災害の危険性が高い。ここでの岩盤移動は主に炭酸塩岩とフリッシュ岩の接触によっておこる。この渓谷の両岸斜面では落石と地滑りの発生が記録されている。これらを考慮するとリエチナ川の河道が落石や地滑りにより閉塞され、洪水イベントが発生する可能性がある。強い降水や地震の発生などは落石や岩石滑りの引き金となり天然ダム崩壊などによる土石流発生の可能性がある。本論文では甚大な規模の斜面崩壊やそれに関る土石流が発生したシナリオおよびモデル構築に関する基本的なアプローチを示す。

Rjecina river is an example of a large torrential watercourse typical for the coastal karst zone of Croatia with its river mouth in the center of Rijeka city. The central part of the watercourse is the most unstable part of the valley, with the highest degree of geological hazard. Here, mass movements are occurring mainly at the contact of carbonate rocks with the flysch rock complex. There are historic data of few rockfalls and landslides on both slopes of the valley. A potential geohazard event could involve movement of slope deposits towards the channel of the Rjecina River. Heavy precipitation and/or earthquakes may be potential triggers of rockfalls and rockslides. So there is a possibility of massive scale landslide occurrence and consequently it can cause several scenarios. Possible scenarios would be investigated furtherly during the Croatia-Japan Joint Project. The paper shows the basic modeling approach for Scenario for Massive scale debris flow occurrence.