Geoscience Reference
In-Depth Information
Chapter 1
INTRODUCTION
Summary of Chapter 1
The objective of this chapter is obviously to introduce the subject of
this research, which is uncertainty in flood forecasting and warning
systems. It starts with defining different types of flood and gives a
brief introduction to the international dimension of the consequences
of flood hazard. A few recent disastrous flood events are also
presented. Secondly, different options of flood management are
described with a more detailed introduction to flood forecasting,
warning and response systems. Next, uncertainty issues in flood
forecasting and warning are discussed, potential benefits of uncertainty
assessment in flood forecasting are presented, the objectives of the
research are set forth and two application examples are introduced. The
structure of this thesis is outlined at the end of this chapter.
1.1
Flood and flood hazard
A flood can be defined as the inundation of a normally dry area caused by an increased
water level in a watercourse or in a body of water. Broadly, flooding can be classified as
river flooding, coastal flooding
and
urban flooding
. This study is limited to the floods in
rivers, which can be characterised by the sudden or gradual increase in water levels,
normally beyond the bank level of the river watercourse and subsequently inundating its
surroundings. From the nature of its occurrence, floods in rivers can be further
distinguished as
flash flooding
and simply
river flooding
. Flash flooding is characterised
by a sudden and massive increase of water quantity (e.g., caused by short intense bursts
of rainfall, commonly from thunderstorms) often combined with mud or debris flows,
leaving endangered communities only limited time to respond. River flooding, on the
other hand, is marked by relatively slowly rising water levels of main rivers and a gradual
inundation of floodplains due to generally continuous long duration rainfall. The former
imposes a different and indeed more daunting challenge to the alertness of flood prone
communities, whereas the larger scope and longer duration of the latter constitutes a
major challenge to the scale and endurance of disaster management arrangements
(Rosenthal et al., 1998). Various definitions of a flood and a comprehensive description
of different types of flooding are presented by Ward (1978).
1.1.1
International dimension of the consequences of flooding
Floods remain one of the most frequent and devastating natural hazards worldwide.
Internationally, floods pose a widely distributed natural risk to life, whereas other natural
hazards such as avalanches, landslides, earthquakes and volcanic activities are more local
