North district – Catchment factor

• Hong Kong has no large rivers. • The larger rivers are mainly in the northwest,

including: Shan Pui River, Shenzhen River, Kam Tin River, Sheung Yue River, and Ng Tung River.

• Mountain• Low lying

The reason of flooding in North district

• Private land developer and government continue change the use of land in north

• Land area use to dredge water greatly reduces due to the reconstruction of land.

• In order to continence the work of drain flooded, government connect the drains directly from Sheung Shui, Fanling Town Centre to Ng tung river

The structure of river in Hong Kong

• Rivers in Hong Kong are generally short and small, without a distinctive middle course. Typically, the upper course is steeper, the middle one gentle while the lower course is nearly flat

• Upper course - steep, many narrow, V-shaped valleys are formed by the prevailing downward erosion

• Lower course - flat terrain, it is easy cause flooding

Shape of river basin in Hong Kong

• From the distribution of tributary(river), three kind of shape are list below :

• Dendritic Drainage Pattern

• Rectangular Drainage Pattern

• Radial Drainage Pattern

• Dendritic Drainage Pattern the most common drainage pattern in Hong Kong

e.g. Lam Tsuen River

• Rectangular Drainage Pattern Appear at regions of the western New Territories

e.g. the upper course of Tuen Mun River

• Radial Drainage Pattern found on roughly conical mountains

e.g. Sunset Peak

The occurrence of Shenzhen River

• Longest river in Hong Kong

• Between New territories and Sham Chun

• Early 90s, lots rainfall lead to flooding

• Main source of flooding in Hong Kong

Before the construction of Shenzhen River

• Bend, meandering taking place

• Poor drainage of water

After the construction of Shenzhen River

• Depth of water increase from 3m to 7m

• Straight• lower course flow

has upgrade • Thread of flooding

Eliminate

Evaluation

• The problem of flooding reduce.

• Amount of silt bring the problem of flooding again

• Poor maintenance