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Pluvial flooding is a critical issue in many cities worldwide and for flood mitigation measures thecauses and characteristics behind pluvial flooding are of interest. Pluvial flooding occurs when
the rainfall amounts exceed the capacity of storm water drains to collect the water and the capacityof the ground to absorb water. This is usually associated with short-duration storms. In thesituation that the frequency of rainfall with strong intensity would increase due to climate change,risk reduction of pluvial floods is further challenge. However, it is hard to understand substantial
characteristics of pluvial floods especially on the scale of city blocks, because they are seldom
measured with instruments. It is also difficult to predict areas prone to the flood caused by heavy
rainfall with a certain intensity. Indeed, even not in the climate change situation, insufficient
capacity of a drainage system, which may be different from that of design, is also anotherimportant factor to cause pluvial floods to cope with these challenges. Modelling approach alone
is not adequate to evaluate the causes and severity of pluvial floods.
If actual from that of design, the primary goals of this study, therefore, is to propose an effective
data collection system for understand substantial characteristics of pluvial floods and applies it tomodels for identifying pluvial flooding processes including drainage models. Utilizing theseresults, the severity of pluvial flood is finally evaluated in relation to controlling factors.
In this study, I set Tsushima, Japan and Yangon, Myanmar as the target areas. These areas suffer
frequently pluvial floods during monsoon seasons and typhoon approach. It could be describedthat the elevation, weather, drainage system, urban development and altitude of the citizens, which
are characterized in each city, are strongly influenced on pluvial flood occurrence and severity. I
presented the water logger monitoring system in urban storm drainage to identify the process ofpluvial floods in both cities during heavy rain. It is also applied to preparation for inundation map
with high resolution terrain data compared with simulation model results. I used New Integrated
Lowland Inundation Model (open source) and InfoWorks ICM (commercial models) to assess thepluvial flood and to explore the effects of sediment depth and other factors in a different storm
drainage system of each city that influence on flood severity.
Pluvial flood severity depends on not only rainfall intensity but also other controlling factors in
the urban area such as sediment depth and garbage clogging inside drainage channels and waterlevel variation of a river that receives the water from drainage systems. Pluvial flood severity isstrongly related to sediment depth in the drains, and duration of flood is more sensitive affects
than flood discharge. Flood inundation map is set based on joint impact of sediment and increased
rainfall that shows where flooding may occur and how severe flood will be over a range of waterlevels in the urban city center.

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We demonstrated that estimating local pluvial flooding process in an urban area using water depth
loggers and a digital elevation model, which are cost-effective and do not require the latest
technology. The results showed recorded water depths in storm water drainage systems could beapplied for tracking the pluvial flooding process by combining it with high-resolution altitude
distribution. The results of modelling demonstrated that considering with open channel storm
drain can retain flood water than without considering open channel storm drain. Because
considering with storm drain has less impacts of floods, while considering without storm drain
has big impacts of floods.
Pluvial flood can occur typically coincide with sediment depth and garbage clogging insidedrainage channels, garbage blockage at trash screen and water level variation of a river thatreceives the water from drainage systems according to the comparison of the logger andsimulation results and site inspection. InfoWorks ICM provides faster calculating time, accurate
flood characteristics of the simulation results like flood depth that can directly compare withlogger depth, special feature like sediment in drain than New Integrated Lowland Inundation
Model (NILIM). All of the simulations with different scenarios by applying InfoWorks ICM ismore effective and efficient for flood risk evaluation and identification for this study. Effluent
capacity of open channels is more sensitive in flooding than closed drain system. Indeed, thepluvial floods often occur closely to the open channel drainage system.
Flood risk management of developing countries have a lot of challenges, not only structural
mitigation measures but also non-structural mitigation measures especially lack of land use
regulation, enforcement of illegal waste disposal, and weakness of collaboration among different
departments. I set pluvial flood risk management governance structure of Yangon, to reduceoverlap and gap in responsibilities and to promote bridging concepts of visions for flood risk
management plans and programs, clear rules of sharing responsibilities among different
departments. I suggested some pluvial mitigation measures based on simulation results and field
inspection that are reliable and achievable.