Flooding occurs when surface water exceeds the carrying capacity of a river channel, causing inundation onto floodplains alongside river banks. Flooding in Hong Kong is classified on a scale from minor to major based on the affected area. Over half of flooding blackspots in Hong Kong are located in the Northern New Territories due to natural factors like weather and catchment features as well as human influence. Upcoming slides will discuss the causes of flooding, measures taken by the government, and evaluations of these efforts.

1. What is flooding ?
• surface water > carrying capacity of the
channel
• exceed bankfull stage
• inundation occurs at flat ground (flood-
plain) alongside the river banks

2. Magnitude of flooding in HK
Blackspot Scales: Major - affecting
area > 100
Medium - affecting hectares
area > 10 hectares
Small - affecting
 serious
 significant
area >0.25 hectares
property socio-
 agricultural
Minor -
affecting area
damage , damage/ economic
isolated serious
< 50x50m
(0.25 hectare) property traffic disruption
 minor damage/
traffic
disruption
public
nuisance and disruption
inconvenience Source: DSD

3. Flooding Blackspots in H.K.
(out of 16 total blackspots)
Northern New Territories
(56%)
Southern New Territories
(13%)
Kowloon (6%)
Islands (25%)
Source : DSD

4. Why in Northern New Territories?

5. Coming up next …
Weather
Natural factors
Catchment
1. Causes of flooding features
Human
influence
2. Measures taken by government to tackle flooding
3. Evaluation of gov.’ s effort and suggestion