Private land developer and government continue change the use of land in north district, agricultural land was converted into car park, high-rise buildings and Container yard etc.Land area use to dredge water greatly reduces due to the reconstruction of land. Natural land has been paved by hard surface. Lead to rainfalls flow into the river directly. In order to continence the work of drain flooded, government connect the drains directly from SheungShui, Fanling Town Centre to Ng tung river, however do not widen the river channels or open another channels, it leads to problem of flooding
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 flatAs the upper course is steep, many narrow, V-shaped valleys are formed by the prevailing downward erosionThe lower course has a flat terrain, it is easy cause flooding
上游的支流往下流方向不斷匯合 ， 主流與支流連結的夾角小於 90 度，就像樹木的主幹與樹枝一樣。Tributaries from the upper course merge with the main stream at fairly regular intervals. The angle between the major channel and its tributaries is less than 90 degrees, similar to that between a tree trunk and its branchesthe major channel and its tributaries are connected at angles close to 90 degree. This can occur if faults and joints in the bedrock are arranged at right angles, so rivers and streams flow and erode along these lines of weaknessRadial drainage patterns comprise several streams that diverge from the same point. Streams and rivers often radiate in all directions from the peaks of mountains.
足以抵禦50年一遇的洪水。淤泥的問題，並就深圳河的水質問題提上議程The place of construction is between, HK zH must have a good communication.
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