Red River, the main river closely attached to Hanoi’s development process, starts from Nguy Son moutain at a height of l,776m in Er Du, Yuanan province; It comes into Vietnam from Ha Khau Gate in the direction of the north west and south east and flows into the Gulf of Tokin at Ba Lat Gate in Nam Dinh. The river is 1,160 km long, including 556km running through Vietnam. Red River flows into Hanoi from Phong Van, Ba Vi district. After going to the north to surround Co Do, Tan Hong, it runs to the east and south at Quang Lang commune, Phu Xuyen district. It covers some 120 km in Hanoi area. The flood on the river is mainly caused by flood at the major estuaries of Da and Lo rivers. Annually, the flood season lasts from June and October in the solar year (coinciding with the rainy season). The Red River dyke was damped from 1108. The section from Nghi Tam to Thanh Tri was called Co Xa dyke. Currently, Red River in Vietnam has around 1,267km dyke on both left and right banks. The dyke surface’s height is 14m.

 
 

Photo: Duong River

Duong River, a branch of Red River, is 65km long and links the big rivers in the north namely Red and Thai Binh rivers. Duong River separates from Red River from Ngoc Thuy commune, Gia Lam district. It flows into the east and the south east and through Thuan Thanh and Gia Luong districts in Bac Ninh. It joins Thai Binh River at Dai Than near Pha Lai. The section through Hanoi is 17.5km long. Duong River had an old name of Thien Duc, Dong Ngan and Bac Giang River.

 
 

Photo: the current To Lich River

To Lich River is the branch of Red River. It separates from Red River from Ha Khau ward at “drain gate of Huong Bai village” where is now Tran Nhat Duat School (Tran Nhat Duat Street). It runs in the direction of the west east to Buoi market and comes to Ha Lieu commune (Thuong Tin-Ha Tay) then joins Nhue River. In 1889, the French Colonialism filled the To branch from the Huong Bai Gate (Ha Khau) to Thuy Khue. From being filled, the river is only the drainage flow for Hanoi and has become seriously polluted.

 
 

Photo: Nhue River

Nhue River is called Tu Liem River. The part near Bat Lang lagoon, Ha Mo commune, Dan Phuong, was very small and the became bigger like a awl, thus, it was called Nhue River. The river runs in the direction of Noth East-South East through Tu Liem, Thanh Tri, Thuong Tin and Phu Xuyen and then joins Day River in Phu Ly town.
Kim Nguu River was a branch of To Lich River running from Yen Lang ward through La Thanh and Nam Dong drain, Phuong Liet ward (Dong Da ) to Thinh Liet commune. Here, it joins Set River and then flows into Thuong Tin (Ha Tay) and meets Nhue River. This is the main branch. There are many other branches flowing within Hai Ba Trung district and Thanh Tri district, but, their main role is serving as the drainage system of the inner city.

Ca Lo River was formerly a branch of Red River, separating from Trung Ha commune, Yen Lac district, Vinh Phuc, some 3 km from Red River. The river has another name called Phu Lo. The tortuous river is located on the boundary between Soc Son districts and Me Minh and Hiep Hoa districts. From August 1, 2008, Ha Tay merged into Hanoi; therefore, the capital city now has additional rivers, including Da River or called Bo or Da Giang River which is natural boundary in the west of Hanoi at present. Starting from Yuanan, China, Da River was in the north west of the old Son Tay province. The section from Che Mountain to Trung Ha is 32km, parallel with Red River, and met a annular drain in Hoa Binh tơn. Thus, it had to run to the north and pour into Thao River before joining Lo River at Hac T-junction.

 
 

Photo: Day River

Day River, or called Hat Giang, is a branch on the right bank of Red River at Hat Mon (or Hat t-junction). This was where Hai ba Trung set up altar to offer gifts and prayers to Heaven before attacking To Dinh’s force. Silt on the river bank was a favorable condition for the appearance of villages growing mulberry, breeding silkworms, weaving fabric. The riverside land area from Dan Phuong to My Duc can grow thousands of hectares of mulberry.

 
 

Photo: Tich River

Tich River originates from the north eastern mountain side of Ba Vi Mountain and flows into the area between Cam Linh and Thuy An commune. This is the main drainage outlet of the Ba Vi mountainous region. All of the rain water from the north eastern mountain side pour into the river. Therefore, the river eroded the area at the mountain foot, creating flat terrain. Here, the river ran tortuously like in the delta region. However, at present, the terrain has been extended with deposits of silt, making the river bed become more sloping and cause erosion again. At that time, the ground surface became harden and turned into laterite, hence, the river does not have a bank like other rivers in the delta region, but sloping similar to ones in the mountainous areas. Tich River is among rare cases in Vietnam. Coming to Xuan Mai, we meet Bui River which runs from Luong Son district, Hoa Binh province. * The water level of Red River is the highest?
Red River starts from Co Do commune, Ba Vi district, to Quang Lang commune, Phu Xuyen district. It is over 100km long with an average annual water flow of 2,640 m3/s and a total water flow of 83.5 million m3. When flood happens, the river’s water surface is some 7m higher than Hanoi streets. In 1971, the river saw the historic flood from the 20th to 2006 with the water level raised up to 14.13m, causing breach in Cong Thon dyke. This was the big flood within 100 years. Besides, Hanoi also witnessed other floods with high water levels of between 12.5 and 13m in 1893, 1904 and 1915, 11.12m in 1924, 11.92m in 1926 (causing breach in Lam Du dyke); The water level in 1945 was measured at 12.68m and 12.7m in 1983. The flood on Red River was the water concentration of the three big rivers of Da, Lo and Thao. When floods happen, the river’s water level can climb up to 0.4m/h and 2.5m/ day. The flood in September 1975 saw the water level of 2.2m/day. Annually, up to 10 floods occurs on Red River from June and October, each can last for one to two week (The flood happening in August 1945 lasted for 14 days, the one in August 1971 lasted for 15 days).