Sediment

1. Reporting about sediment disasters in Cagayan River Basin, Philippines
   1. Sediment: some information about it
      1. In Magat River, a major infrastructure for irrigation and hydropower, bathymetric surveys showed that more than 30% reservoir trapping efficiency is reduction. Annual average sedimentation rate in the reservoir of 20 MCM/yr which is 5.5 times higher than the design. The rate of siltation in the live storage is 16.3 MCM/yr and 3.7m MCM/yr in the dead storage. Hence, it is expected that the power generation will cease most probably within 5 years without partial flushing implementation, while the irrigation service area will be reduced by 393 ha/yr
   2. Landslides (Cagayan Valley Regional Disaster Risk Reduction and Management Council, 2020)
      1. Typhoon Quinta (Oct 27, 2020)-series of landslides were reported along the National highway in Cagayan province particularly in the municipalities of Sta. Praxedes, Claveria and Sta Ana.
      2. NE Monsoon enhanced by Typhoon Vicky (Dec 18-20, 2020)-landslide incidents were reported in the provinces of Nueva Vizaya and Cagayan within the CRB with details below.

         

      3. Tail-end of a cold front and Typhoon Ulysses (Nov 8-13, 2020)-there were 9 landslides across the region with details below

         

      4. Tail-end of a frontal system and NE monsoon (Nov 28 - Dec 18, 2020)-2 landslides reported with details below

         

      5. Typhoon Pepito (Oct 19-Oct 22, 2020)-there were 9 landslides reported in the region with details below

         

         Localized thunderstorm and SW monsoon (Oct 11-13, 2020) - Sta. Fe road in the Natioanl Hiway was unpassable due to landslide along with 3 local roads.

      6. Northeasterly surface windflow in the region (Oct 16-18, 2020) - 4 landslides were reported in Baggao, Cagayan with details below.

         

      7. TD Ofel (Oct 13-15, 2020) - 1 person evacuated due to landslide threat

      -		Cagayan	Isabela	Nueva Vizcaya	Quirino	Batanes	Total
      Aftermath of Typhoon Quinta (December 2020) Waist to Knee-deep level	Number of Affected Brgys.	3	-	-	-	-	3
      	Number of Affected Persons	-	-	-	-	-	-
      	Number of Casualty	-	-	-	-	-	-
      Aftermath of the Northeasterly Surface Wind flow *1 parially damaged house	Number of Affected Brgys.	4	-	-	-	-	4
      	Number of Affected Persons	-	-	-	-	-	-
      	Number of Casualty	-	-	-	-	-	-
      Tail-end of a cold front and Typhoon Ulysses (Nov 8-13, 2020)	Number of Affected Brgys.	5	-	3	1	-	8
      	Number of Affected Persons	-	-	-	-	-	-
      	Number of Casualty	4	-	10	-	-	14
      Tail-end of a frontal system and NE monsoon (Nov 28 - Dec 18, 2020)	Number of Affected Brgys.	4	-	-	-	-	4
      	Number of Affected Persons	-	-	-	-	-	-
      	Number of Casualty	-	-	-	-	-	-
      NE Monsoon enhanced by Typhoon Vicky (Dec 18-20, 2020)	Number of Affected Brgys.	1	-	-	4	-	5
      	Number of Affected Persons	-	-	-	-	-	-
      	Number of Casualty	-	-	-	-	-	-

2. Reporting about sediment disasters in Vu Gia-Thu Bon Basin, Vietnam
   1. Landside

      In 2020, Quang Nam has 7 major landslides, 46 deaths.

      

      

      

   2. Erosions

      

      Table 1: The erosion information at major erosion sites (field survey, March 2021)

      No.	River	X	Y	Location	Contents
      1	ThuBon	15.866933	108.241967	Hoi An, Quang Nam	The right bank is strongly eroded, with a length of about 1200m The largest erosion width is about 150m, the average erosion width is about 80m Erosion height is about 2.4m Erosion shape: vertical slide The location of the strongest erosion has coordinates: 15.86302522, 108.23836718 The left bank is slightly eroded
      2	ThuBon	15.869333	108.170117	Dien Tho, Dien Ban, Quang Nam	At the location of the curved river and the location where sand is mining (6 machines are sucking sand) The left bank is eroding strongly and is continuing to erode The erosion length is 1600m, the erosion height is 2m - 5m. Right bank is eroding but stabilized
      3	ThuBon	15.848107	108.140508	Dai Hoa, Dai Loc, Quang Nam Hạ lưu cầu Giao Thủy	Located at sand mining site (10 machines are exploiting sand) The left bank is strongly eroded, the erosion length is about 1110m. Erosion height 3.5m Sand mining leaves large gravel beds to emerge out of the water The right bank is an alluvial ground
      4	ThuBon	15.824577	108.086903	Dai Thang, Dai Loc, Quang Nam	Both banks are moderately eroded Sand mining greatly changes the topography of the riverbed, some locations have large local depths Sand mining leaves large gravel beds to emerge out of the water, especially on the left bank
      5	Quang Hue	15.845017	108.114154	Cửa ra sông Quang Hue giao với sông Thu Bon	o The right bank has a large erosion of about 360m, the erosion height increases gradually to the outlet from 1m - 5m, the erosion is vertical. The embankment works but has been damaged in part, the rest is damaged at the foot of the embankment The left bank is alluvial ground, near the sand mining site, so erosion areas appear The size of sand on the riverbed and on the banks of the Quang Hue river is larger than in the Thu Bon River The water of Quang Hue river is more turbid than Thu Bon river, at the intersection, it creates two distinctly different turbidity waters
      6	Vu Gia	15.866729	108.062721	Dai Phong, Dai Loc, Quang Nam	There are 6 machines mining sand at the erosion site Both banks are eroded, the length of the erosion is about 920m, the height of erosion is 1m - 3m Greater erosion on the left bank
      7	Vu Gia	15.848948	108.019589	Dai Quang, Dai Loc, Quang Nam	o There are 3 machines that are mining sand o Erosion on the right bank is about 200m in length, 0.5 - 1.5m in height o The roof embankment is damaged
      8	Vu Gia	15.85551	107.98033	Dai Hong, Dai Loc, Quang Nam	There are 6 machines that are mining sand Erosion is very large on both sides, erosion is continuing The right bank is about 1600m long, about 3.5m high The left bank is about 370m long, about 1.5m high
      9	Vu Gia	15.83466	107.933318	Dai Lanh, Dai Loc, Quang Nam	The right bank is very strongly eroded, the erosion length is about 2500m, the height is from 1m - 5.5m, the average width is 50m. The location of the strongest erosion is at coordinates 15.83449589, 107.93434381 Many people's houses have been drifting down into the river, some houses inside are in danger of erosion, people have to move The left bank is slightly eroded, about 0.5m high Location of sand mining, leaving large gravel yards at the bottom of the river
      10	Bung	15.821184	107.835974	Dai Son, Dai Loc, Quang Nam	The left bank at the position of the curved river section is strongly eroded, the erosion length is about 220m, the height is 4m The size of gravel on the bottom of the river is large, there is a large gravel beach emerging on the left bank The water is clearer than Vu Gia and Con Rivers
      11	Lac Thanh	15.939786	108.181309	Dien Hoa, Dien Ban, Quang Nam	Left bank erosion (on railway bridge), erosion length about 550m, height 1m-3m Sand mining paused, due to major erosion On the left bank, there is a sand mining site
      12	Qua Giang	15.970807	108.205385	Hoa Phuoc, Hoa Vang, Da Nang	The left bank is strongly eroded (above the Qua Giang bridge, the position of the river is curved) about 710m in length, about 0.5m - 2.5m in height. The right bank is heavily eroded with a length of about 300m, a height of 0.5m - 2m Vertical slip erosion