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Abstract
Flooding Pattern
ConclusionStudy Area
Acknowledgement
Maps and charts
Flooding in Bangladesh coast is generally classified into four
types. These are fluvial flood, tidal flood, fluvio-tidal flood and
storm surge flood. Except storm surge flood, the other three types
of flood are caused by fluvial flows from the upstream rivers
systems of Ganges-Brahmaputra-Meghna and tides from the Bay
of Bengal. Polders are constructed in the coastal region as a
protective measure from tidal flood and salinity. These protective
measures divided the coastal floodplains into protected and non-
protected areas. It is generally expected that protected part inside
the polder will remain flood-free from the types of flood mentioned
above except during the situation when polders are overtopped by
the surrounding river water. Depending on the flood protection
measures and sources of flood water, flooding patterns in the non-
protected part of the coast behaves in a complicated manner. So
far there is no comprehensive study to investigate this flooding
pattern. In this study we have applied the Delft 3D model to study
the coastal flooding pattern in both protected (when polders are
overtopped) and non-protected part of the region. It is found that
fluvial flooding is characteristically different from the fluvio-tidal
flooding and tidal flooding. Fluvial flooding is confined in the
northern part of the coast whereas tidal flooding is confined in the
southern part. There are scattered part in the region where
flooding is found to be caused by both fluvial flow and tide. These
floods are considered to fluvio-tidal. This information will be useful
for the planning purpose when further interventions are planned in
the coast.
Fluvial Flooding
Tidal
Flooding
Fluvio-tidal
Flooding
Fig 1: ESPA Study Area
Inundation Map
1998 2000
1998 2000
Fig 2: Inundation Maps
Fig 3: Three types of Flooding
Flooding patterns in Bangladesh Coast
There are 4550 Unions in Bangladesh from which a subset of 653 Unions
are selected for ESPA study area. Here all these 653 unions are
categorized with respect to their flooding pattern in the non-protected part
and are shown in Fig 4. Year 1998 is selected as an extreme flood event
and year 2000 is selected as an average flood event in the region.
Fatin Nihal, Shanjida Noor, Anisul Haque, Munsur Rahman, Delowar Hossain
Institute of Water and Flood Management (IWFM)
Bangladesh University of Engineering and Technology
Three types of flooding patterns have found in the non-protected
part of the study area. Among 653 unions in the study area,
fluvial flood is the most dominating flood type followed by fluvio-
tidal and tidal floods. Fluvial flooding is confined in the northern
part of the coast whereas tidal flooding is confined in the
southern part. There are scattered part in the region where
flooding is found to be caused by both fluvial flow and tide. In an
average flood event 20%, 5% and 6% areas of the region is
flooded by fluvial flood, tidal flood and fluvio-tidal flood
respectively which is increased to 38%, 6% and 11% during an
extreme event.
Fig 4: Maps and pie charts for 653 unions
1998 2000