Li-Pen Wang

National Taiwan University | NTU · Department of Civil Engineering

Spatial and temporal variability of rainfall input plays a critical role on the performance of the urban runoff simulations. For this reason, urban hydrological application demands accurate products of high-resolution and high-quality rainfall estimates, which use and understanding become critical for more robust models. In this study, the spatial...

Stochastic rainfall models are commonly used in practice for long-term flood risk management. One of the most widely used model types is based on point processes. Despite the widespread use of such models, whether their known simplifications in describing the space-time structure of rainfall will affect the accuracy of flood estimation has not been...

The use of Poisson cluster processes to model rainfall time series at a range of scales now has a history of more than 30 years. Among them, the randomised (also called modified) Bartlett-Lewis model (RBL1) is particularly popular, while a refinement of this model was proposed recently (RBL2; Kaczmarska et al., 2014). Fitting such models essentiall...

FloodCitiSense aims at developing an urban pluvial flood early warning service for, but also by citizens and city authorities, building upon the state-of-the-art knowledge, methodologies and smart technologies provided by research units and private companies. FloodCitiSense targets the co-creation of this innovative public service in an urban livin...

The use of Poisson-cluster processes to model rainfall time series at a range of scales now has a history of more than 30 years. Among them, the Randomised (also called modified) Bartlett–Lewis model (RBL1) is particularly popular, while a refinement of this model was proposed recently (RBL2) (Kaczmarska et al., 2014). Fitting such models essential...

Radar-rain gauge merging techniques have been widely used to improve the applicability of radar and rain gauge rainfall estimates by combining their advantages, while partially overcoming their individual weaknesses. Despite significant research in this area, guidance on the suitability of, and factors affecting merging techniques at the fine spati...

This paper proposes a new object-based storm tracking algorithm, based upon TITAN (Thunderstorm Identification, Tracking, Analysis and Nowcasting). TITAN is a widely-used convective storm tracking algorithm but has limitations in handling small-scale yet high-intensity storm entities due to its single threshold identification approach. It also has...

Fractal analysis relies on scale invariance and the concept of fractal dimension enables one to characterize and quantify the space filled by a geometrical set exhibiting complex and tortuous patterns. Fractal tools have been widely used in hydrology but seldom in the specific context of urban hydrology. In this paper, fractal tools are used to ana...

Fractal analysis relies on scale invariance and the concept of fractal dimension enables to characterise and quantify the space filled by a geometrical set exhibiting complex and tortuous patterns. Fractal tools have been widely used in hydrology but seldom in the specific context of urban hydrology. In this paper fractal tools are used to analyse...

Pluvial flood nowcasting is gaining ground not least because of the advancements in rainfall forecasting schemes. Short-term forecasts and applications have benefited from the availability of such forecasts with high resolution in space (∼1km) and time (∼5min). In this regard, it is vital to evaluate the potential of nowcasting products for urban i...

This study compares two nonparametric rainfall data merging methods—the mean bias correction and double-kernel smoothing—with two geostatistical methods—kriging with external drift and Bayesian combination—for optimizing the hydrometeorological performance of a satellite-based precipitation product over a mesoscale tropical Andean watershed in Peru...

Gauge-based radar rainfall adjustment techniques have been widely used to improve the applicability of radar rainfall estimates to large-scale hydrological modelling. However, their use for urban hydrological applications is limited as they were mostly developed based upon Gaussian approximations and therefore tend to smooth off so-called "singular...

It is a common practice to assign the return period of a given storm event to the urban pluvial flood event that such storm generates. However, this approach may be inappropriate as rainfall events with the same return period can produce different urban pluvial flooding events, i.e., with different associated flood extent, water levels and return p...

Following extensive surface water flooding (SWF) in England in summer 2007, progress has been made in improving the management and prediction of this type of flooding. A rainfall threshold-based Extreme Rainfall Alert (ERA) service was launched in 2009 and superseded in 2011 by the Surface Water Flood Risk Assessment (SWFRA). Through survey respons...

Rainfall estimates of the highest possible accuracy and resolution are required for urban hydrological applications, given the small size and fast response which characterise urban catchments. While radar rainfall estimates have the advantage of well capturing the spatial structure of rainfall fields and its variation in time, the commonly availabl...

Urban catchments are typically characterised by high spatial variability and fast runoff processes resulting in short response times. Hydrological analysis of such catchments requires high resolution precipitation and catchment information to properly represent catchment response. This study investigated the impact of rainfall input resolution on t...

Gauge-based radar rainfall adjustment techniques have been widely used to improve the applicability of radar rainfall estimates to large-scale hydrological modelling. However, their use for urban hydrological applications is limited as they were mostly developed based upon Gaussian approximations and therefore tend to smooth off so-called "singular...

This study investigates the impact of rainfall estimates of different spatial resolutions on the hydraulic outputs of the models of four of the EU RainGain project's pilot locations (the Cranbrook catchment (UK), the Herent catchment (Belgium), the Morée‐Sausset catchment (France) and the Kralingen District (The Netherlands)). Two storm events, one...

The applicability of the operational radar and raingauge networks for urban hydrology is insufficient. Radar rainfall estimates provide a good description of the spatiotemporal variability of rainfall; however, their accuracy is in general insufficient. It is therefore necessary to adjust radar measurements using raingauge data, which provide accur...

The work presented here is a contribution to the Thames Water project of improving the Counters Creek catchment sewerage system in London. An increase in the number of floods affecting basements in the area has indicated the need for improvements to the system. The cost of such improvements could be very high, and as such it is important to determi...

This paper presents an approach to enhance the role of local stakeholders in dealing with urban floods. The concept is based on the DIANE-CM project (Decentralised Integrated Analysis and Enhancement of Awareness through Collaborative Modelling and Management of Flood Risk) of the 2nd ERANET CRUE funding initiative. The main objective of the projec...

A nowcasting model coupled with an urban drainage model is used in this study to assess the forecasting of pluvial floods in urban areas. The deterministic nowcasting model used in this paper is part of the Met Office STEPS (Short-Term Ensemble Prediction System) system, and the hydraulic model is run based on the ID/ID dual drainage simulation sch...

This paper presents the main findings and lessons learned from the development and implementation of a new methodology for collaborative modelling, social learning and social acceptance of flood risk management technologies. The proposed methodology entails three main phases: (1) stakeholder analysis and engagement; (2) improvement of urban pluvial...

A more reliable flood forecasting could benefit from higher-resolution rainfall forecasts as inputs. However, the prediction lead time of the operational rainfall forecasting models will substantially diminish while sub-hourly (e.g., 5-min) rainfall forecasting is required. A method that integrates the SVM (Support Vector Machine) and Cascade-based...

For reliable prediction of urban pluvial flooding it is essential to have reliable spatial and temporal rainfall prediction at an appropriate scale. Radar data are considered to be the most reliable. However, many urban catchments do not have access to radar data. This paper presents a new methodology for rainfall forecasting based on a network of...

Short-term surface flood modelling requires reliable estimation of the distribution of floods over urban catchments with sufficient lead time in order to provide timely warnings. In this paper new improvements to the traditional Support Vector Machine (SVM) prediction technique for rainfall prediction are presented. The results obtained using the n...

In order to effectively prevent, mitigate and manage urban pluvial flooding, it is necessary to accurately model and predict the spatial and temporal distribution of both rainfall and surface flooding. A number of different modelling and prediction techniques have been applied to three UK case studies. The case studies illustrated potential improve...

The current European Directive for Flood Risk Management (FRM) requires a demand-driven approach in which policy makers work together with practitioners and the general public in preparation of FRM plans and actions. In that context, the DIANE-CM project, funded by the 2nd ERANET-CRUE initiative proposes an innovative approach which brings the conv...

The theory of Multifractals has been widely applied to modelling spatial and/or temporal distributions of rainfall by characterising their scale-invariant features. Random cascade methods are the main tool in this field to simulate rainfall structures by constructing generators. However, the type and parameters of generators strongly depend upon th...

This work aims to develop a semi-deterministic multiplicative cascade method for producing reliable short-term (sub-daily) rainfall sequences. The scaling feature of sub-daily rainfall sequences is analysed over the timescales of interest (i.e., 5 min to hourly in this research) to help derive the crucial parameters, i.e., the fragmentation ratios,...

The concept of an improved rainfall model is introduced in this paper, which aims to increase the lead time of the state-of-the-art short-term rainfall forecast modelling so that the operational surface flooding models enable to estimate reliable flood distribution.Apractical methodology proposed by thiswork is to generate finer-resolution rainfall...

This work aims to develop a semi-deterministic multiplicative cascade method for producing reliable short-term (sub-daily) rainfall sequences. The scaling feature of sub-daily rainfall sequences is analysed over the timescales of interest (i.e., 5 min to hourly in this research) to help derive the crucial parameters, i.e., the fragmentation ratios,...

The authors would like to appreciate the referee's insightful comments on this work and for generously providing useful references to help understand the deficiency of this paper. In the following, the authors would like to respond to the issues raised in the comments following the titles in the referee's supplementary detailed comments.