1. REALTIME FORECASTING OF SHALLOW LANDSLIDES USING RADAR-DERIVED RAINFALL Ryohei Misumi, Masayuki Maki, Koyuru Iwanami, Ken-ichi Maruyama and Sang-Goon Park National Research Institute for Earth Science and Disaster Prevention, Japan By

2. Shallow landslide at Izumozaki-town, Niigata Prefecture on 13 July 2004

3. Outline X-band polarimetric radar Distributed rainfall- runoff model Real-time forecast of landslides Soil water Rainfall estimation in high accuracy and resolution

4. Weight Bed rock Soil layer Slip surface Sliding force Shear resistance Normal situation What is shallow landslide ?

5. Bed rock Soil layer Saturated Zone Soil particles Water During heavy rainfall Increase of pore pressure Decrease of normal stress Rain

6. Estimation of rainfall intensity using the specific differential phase (K DP )  not affected by rain attenuation  immune to beam blockage  less sensitive to beam filling and drop size distribution ＋ ＋ ZK DP

7. Disdrometer + R-K DP R-Z R-Z (corrected)

8. Catchment 50m grid Rainfall Distributed rainfall-runoff model Evaporation Infiltration Direct runoff Base flow Maximum storage capacity S max Water storage S 50m grids

9. Infinite slope stability analysis F: Factor of safety γ, c', Φ': Soil properties γ w : Density of water h: Level of groundwater z: Depth of soil β: Inclination of slope

10. 80km Tsurumi river basin MP-X radar Real-time evaluation

11. Meso-β scale depression on 9 July 2005 22:59 Rainfall rate Water storage Predicted landslides

12. Meso-β scale depression on 9 July 2005 23:29 Rainfall rate Water storage Predicted landslides

13. Meso-β scale depression on 9 July 2005 23:53 Rainfall rate Water storage Predicted landslides

14. 3 km Actual landslide Predicted grid Landslide on 9 July 2005

15. Evaluation with past events Upper Abukuma River basin (151.07km 2 ) Rainfall event in August 1998

16. 043215 02JST on 27 August (2 hours before severe landslides) Distance (km) Slope failure Predicted grids Welfare facility

17. Predicted factor of safety (F) and occurrence of landslides Factor of safety OccurNot occur F < 1205 grids1809 grids F > 156 grids5318 grids Correct forecasts: 74.8 % False alarm ratio: 89.8 %

18. Conclusions  An accurate forecast of shallow landslides is still difficult.  Increase of landslide potential in a few-km scale may be predictable using rainfall observation with the X-band polarimetric radar (lead time is about 2 hours).  The lead time would be greatly extended if a reliable QPF is available.