River modelling for flood risk map prediction
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Date
2009
Authors
Alaghmand, Sina
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Abstract
The research illustrates an importance of river flood in urban areas which cause
lost of lives and properties damages. Knowledge on the river basin response to rainfall
events of runoff is vital in engineering practices for urban planning and development.
Flood hazard map prediction is a combination of hydrological modelling, hydraulic
modelling and river flood visualization using GIS. The case study of this research is
Sungai Kayu Ara located in Damansara, Kuala Lumpur. A total of 36 scenarios are
identified in order to assess the effects of rainfall magnitude (20 year, 50 year and 100
year ARI) and duration (60, 120, 180 and 360 minutes) for existing, intermediate and
ultimate development conditions. The results of hydrological model simulation indicated
that, an increase in the rainfall magnitude leads to increase of runoff volume and peak
discharge while increase of rainfall event duration increases the runoff volume but
decreases the runoff peak discharge. Furthermore, an ultimate river basin development
conditions (90% imperviousness) generate higher runoff volume and peak discharge in
comparison with existing and intermediate development conditions. The river flood
hazard maps are generated based on water depth, flow velocity and combination of
water depth and flow velocity. These maps showed that the impact of water depth is
more considerable than flow velocity during river flood. Hence, hazard attributed to
water depth is more significant in comparison with flow velocity. River flood hazard
maps are the base of the river flood risk prediction. River flood risk maps are considered
as the function of river flood hazard, vulnerability and exposure. In this case, land-use
type, main road accessibility and debris flow are involved to reflect the terms
vulnerability and exposure in river flood risk map prediction. These four elements are
provided as GIS raster layers in which all pixels indicate the severity value of each
element. The generated river flood risk map is the result of combination of four main
elements, river flood hazard, land-use type, main road accessibility and debris flow. The
suggested method for river flood risk map prediction recommends four classes of
severity for river flood consists of, low, medium, high and extreme. The established
flood risk prediction map has shown that the river flood hazard, debris flow hazard,
land-use type and main road accessibility have significant impact and able to facilitate
the planning and management of river flooding in urban areas. The variation of
predicted river flood risk pattern is a function of river flood hazard and debris flow
hazard patterns; as the distribution of hazards produced by land-use type and main road
accessibility is uniform.
Description
Master
Keywords
River modelling , Flood risk map