Weather Radar and Hydrology Edited by

Abstract This paper aims to present the operation of the AIGA flood warning system. Developed by Cemagref and Météo-France, this method combines radar rainfall and a simple distributed hydrological model taking into account antecedent soil moisture conditions. Discharges are calculated at ungauged points on the river network and compared to statistical reference values. Depending on the occurrence level of the on-going event, different warnings are emitted in real-time. The case study presented focuses on the dramatic event of 15 June 2010 in the area surrounding the town of Draguignan, south of France.

Key words flood warning system; ungauged catchments; post event analysis

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 556-561

Uncertainty estimation of deterministic river basin response simulations at gauged locations
Zachary L. Flamig¹, Emmanouil Anagnostou²,
Jonathan Gourley³ & Yang HONG¹

1 Atmospheric Radar Research Center, University of Oklahoma, 120 David L. Boren Blvd. Norman, Oklahoma 73072, USA

[e-mail]

2 Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Rd, UNIT-2037, Storrs,
Connecticut 06269, USA

3 NOAA/National Severe Storms Laboratory, 120 David L. Boren Blvd. Norman, Oklahoma 73072, USA
Abstract This study presents a method to supply uncertainty estimates to flood predictions based on deterministic river basin response simulations from an uncalibrated, distributed hydrological model. A
15-year radar rainfall archive was used to run a hydrological model, thus providing a time series of simulated flows at every model grid cell. At grid cells corresponding to streamgauge locations, the time periods at which observed streamflow exceeded pre-computed observed flow frequency thresholds (e.g. 2-, 5-, 10-year return period flows) were identified. The distributions of simulated flows within (i.e. flooding at the respective frequency threshold) and outside (non-flooding at the respective frequency) these time intervals were then computed. The accuracy of the method is evaluated during an independent validation period where probabilities of flood >0.9 during flood cases are predicted more than 90% of the time, while probabilities of flood equal to zero occurred 75% of the time during non-flood cases.

Key words flood; distributed hydrological model; uncertainty estimation; probabilistic forecasting

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 562-567.

Flash flood forecasting using Data-Based Mechanistic models and radar rainfall forecasts
Paul j. smith¹, keith beven¹, luca panziera² & Urs germaNn²

1 Lancaster Environment Centre, Lancaster University, UK

[e-mail]

2 MeteoSwiss, Locarno Monti, Switzerland
Abstract The parsimonious time series models used within the Data-Based Mechanistic (DBM) modelling framework have been shown to provide reliable accurate forecasts in many hydrological situations. In this work the DBM methodology is applied to forecast discharges during a flash flood in a small Alpine catchment. In comparison to previous work this catchment responds rapidly to rainfall. It is demonstrated, by example, that the use of a radar-derived ensemble quantitative precipitation forecast coupled to a DBM model allows the forecast horizon to be increased to a level useful for emergency response. A treatment of the predictive uncertainty in the resulting hydrological forecasts is discussed and illustrated.

Key words DBM; NORA; flash flood; IMPRINTS; Verzasca

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 568-573.

Urban flood prediction in real-time from weather radar and rainfall data using artificial neural networks
Andrew P. Duncan, Albert S. Chen, Edward C. Keedwell, Slobodan Djordjević & Dragan A. Savi



Centre for Water Systems, University of Exeter, Harrison Building, North Park Road, Exeter EX4 4QF, UK

[e-mail]
Abstract This paper describes the application of Artificial Neural Networks (ANNs) as Data Driven Models (DDMs) to predict urban flooding in real-time based on weather radar and/or raingauge rainfall data. A
123-manhole combined sewer sub-network from Keighley, West Yorkshire, UK is used to demonstrate the methodology. An ANN is configured for prediction of flooding at manholes based on rainfall input. In the absence of actual flood data, the 3DNet / SIPSON simulator, which uses a conventional hydrodynamic approach to predict flooding surcharge levels in sewer networks, is employed to provide the target data for training the ANN. The ANN model, once trained, acts as a rapid surrogate for the hydrodynamic simulator. Artificial rainfall profiles derived from observed data provide the input. Both flood-level analogue and flood-severity classification schemes are implemented. We also investigate the use of an ANN for nowcasting of rainfall based on the relationship between radar data and recorded rainfall history. This allows the two ANNs to be cascaded to predict flooding in real-time based on weather radar.

Key words artificial neural network; manhole; multi-layer perceptron; nowcasting; prediction; rainfall; urban flood; weather radar

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 574-580

Contribution of weather radar data to hydropower generation optimization for the Rhone River (France)
Benjamin GRAFF¹, Dominique FAURE², Guillaume BONTRON¹ & SEBASTIEN LEGRAND¹

1 Compagnie Nationale du Rhône, 2, rue André Bonin, 69316 Lyon Cedex 04, France

[e-mail]

2 Alicime, 14 rue du Docteur Bordier, 38100 Grenoble, France
Abstract CNR operates 19 hydropower plants all along the Rhone River in France. To forecast hydropower generation and to ensure the security of people and plants, CNR has developed hydrometeorological forecasting tools, rainfall–runoff modelling and propagation models, for the Rhone River and some of its main tributaries. With the assistance of Alicime, CNR achieved an application named AEGIR to integrate radar QPE into its hydrometeorological forecasting process. AEGIR allows CNR: to assess spatial rainfall pattern and rainfall variability in time and space over the Rhone River basin; to compare radar QPE and observed raingauge measurements; to forecast rainfall hyetograph for each sub-basin of the Rhone River. The paper focuses on the contribution of radar QPE regarding CNR’s purposes, by analysing the quality of observed and forecasted radar quantitative estimates over the Rhone River basin, and finally assessing the operational use of radar QPE as an input into pre-existent rainfall–runoff models.

Key words weather radar; QPE; rainfall–runoff forecasting; Rhone River; hydropower generation

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 581-586

Relations between streamflow indices, rainfall characteristics and catchment physical descriptors for flash flood events
P. A. Garambois^1,2, H. Roux^1,2, K. Larnier^1,2 & D. Dartus^1,2

1 Université de Toulouse, INPT, UPS, IMFT (Institut de Mécanique des Fluides de Toulouse), F-31400 Toulouse, France

[e-mail]

2 CNRS; IMFT; F-31400 Toulouse, France
Abstract Flash flood is a very intense and quick hydrologic response of a catchment to rainfall. This phenomenon has a high spatial-temporal variability as the generating storm often hits small catchments (few km²). Given the small spatial-temporal scales and high variability of flash floods, their prediction remains a hard exercise as the necessary data are often scarce. This study investigates the potential of hydrologic indices at different scales to improve understanding of flash floods dynamics and characterize catchment response in a model independent approach. These hydrologic indices gather information on hydrograph shape or catchment dynamic for instance and are useful to examine catchment signature in function of their size. Results show that for middle-size (>100 km²) catchments response shape can be correlated to storm cell position within the catchment contrarily to smaller catchments. In a multi-scale point of view, regional characteristics about catchment geomorphology or rainfall field statistics should provide useful insight to find pertinent hydrologic response indices. The combined use of these indices with a physically-based distributed modelling could facilitate calibration on ungauged catchments.

Key words flash flood; hydrologic indice; ungauged catchment

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 587-592.

Radar for hydrological modelling: new challenges in water quality and environment
M. Bruen

Centre for Water Resources Research, School of Civil, Structural and Environmental Engineering, Newstead Building, University College Dublin, Belfield, Dublin 4, Ireland

[e-mail]
Abstract Any exploration of actual and potential uses of radar information in hydrological models must start with a survey of actual and potential uses of hydrological models. Their early history is closely associated with the increasing availability of computing power while the more recent past shows an increasing range of applications. Early developments were for water resources management, floods and droughts, but the range of potential uses has expanded considerably. For instance, in Europe, the requirements of the EU Water Framework Directive will increase the use of either distributed or semi-distributed models in “design” mode to identify critical source areas contributing contaminants and sediment to rivers and lakes. The critical sources areas can be a small percentage of the total catchment area, but contribute most of the sediment and a lot of the associated particulate contamination. The rainfall climatology at such small scales may be developed from radar records and may be important for the management of risk if there is significant spatial variability at such scales. In the past, radar-based rainfall forecasts would only be used for river flow forecasting; however their use can be extended to such water quality applications as forecasting bathing water quality on beaches as a public information service.

Key words hydrological modelling; radar; Water Framework Directive; Floods Directive

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 595-600.

Advances in the application of radar data to urban hydrology
Hans-Reinhard Verworn

Institute for Water Resources Management, Leibniz University, Appelstr. 9A, 30167 Hannover, Germany

[e-mail]
Abstract When radar data are to be used in urban hydrology a few special aspects have to be considered. The smaller scales in time and space require a higher resolution and rapid availability if utilised for real-time applications, and have consequences for the processing of data. This review focuses on some of the problems and the developments and improvements in recent years.

Key words urban hydrology; urban drainage; radar rainfall data; nowcasting

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 601-606

What is a proper resolution of weather radar precipitation estimates for urban drainage modelling?
Jesper E. Nielsen, michael R. Rasmussen & Søren ThorndaHl

Aalborg University, Department of Civil Engineering, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark

[e-mail]
Abstract The resolution of distributed rainfall input for drainage models is the topic of this paper. The study is based on data from high-resolution X-band weather radar used together with an urban drainage model of a medium-sized Danish village. The flow, total runoff volume and CSO volume are evaluated. The results show that the model to some extent is dependent on the rainfall input resolution and recommendations for the resolution are given. However, none of the investigated resolutions can be characterized as “unusable”.

Key words weather radar measurements; urban drainage modelling; MOUSE; radar data resolution: LAWR

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 607-613.

The flooding potential of convective rain cells
efrat Morin & hagit yakir

Geography Department, Hebrew University of Jerusalem, Jerusalem 91905, Israel

[e-mail]
Abstract Flash floods caused by convective rain storms are highly sensitive to the space–time characteristics of rain cells. In this study we exploit the high space–time resolution of the radar data to study the characteristics of the rain cells and their impact on flash flood magnitudes. A rain cell model is applied to the radar data of an actual storm and the rain fields represented by the model further serve as input into a hydrological model. Global sensitivity analysis is applied to identify the most important factors affecting the flash flood peak discharge. As a case study we tested an extreme storm event over a semi-arid catchment in southern Israel. The rain cell model was found to simulate the rain storm adequately. We found that relatively small changes in the rain cell’s location, speed and direction could cause a three-fold increase in flash flood peak discharge at the catchment outlet.

Key words convective rain cells; flash floods; weather radar

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 614-619.

Analysis of different quantitative precipitation forecast methods for runoff and flow prediction in a small urban area
ALMA SCHELLART¹, SARA LIGUORI², STEFAN KRÄMER³, ADRIAN SAUL⁴ & MIGUEL RICO-RAMIREZ²

1School of Engineering, Design and Technology, University of Bradford, Richmond Road, Bradford BD7 1DP, UK

[e-mail]

2 Department of Civil Engineering, University of Bristol, Bristol BS8 1TR, UK

3 Institute for Technical and Scientific Hydrology (itwh) Ltd., Engelbosteler Damm 22, 30167 Hanover, Germany

4 Dept. of Civil and Structural Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK
Abstract Due to the relatively small spatial scale as well as rapid response of urban drainage systems, the use of quantitative rainfall forecasts for providing quantitative flow forecasts is a challenging task. Due to urban pluvial flooding and receiving water quality concerns it is, however, worthwhile to investigate the potential. In this paper, two radar nowcast models have been compared and used to create quantitative forecasts of sewer flows in the centre of a small town in the north of England.

Key words urban; rainfall–runoff; radar nowcasting; (NWP) flow forecasting; urban drainage

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 620-625.

On comparing NWP and radar nowcast models for forecasting of urban runoff
S. Thorndahl¹, T. Bøvith², M. R. Rasmussen¹ & R. S. Gill²

1 Aalborg University, Department of Civil Engineering, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark

[e-mail]

2 Danish Meteorological Institute, Lyngbyvej 100, DK-2100 Copenhagen Ø, Denmark
Abstract The paper compares quantitative precipitation forecasts using weather radars and numerical weather prediction models. In order to test forecasts under different conditions, point-comparisons with quantitative radar precipitation estimates and raingauges are presented. Furthermore, spatial comparisons of forecasts and observations have shown good results during stratiform conditions, but more scattered results during convective conditions. Finally, the potential for applying forecasts as input to urban drainage models is investigated. Results prove promising.

Key words numerical weather prediction; radar nowcasting; QPE; QPF; urban flow forecasting

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 626-631.

Decision support for urban drainage using radar data of HydroNET-SCOUT
Arnold lOBBRECHT^1,2, thomas eINFALT³, leanne REICHARD¹ & irene pOORTINGA¹

1 PO Box 2177, 3800 CD Amersfoort, the Netherlands

[e-mail]

2 UNESCO-IHE, PO Box 3015, 2601 DA Delft, the Netherlands

3 Hydro & meteo GmbH&Co.KG, Breite Str. 6-8, 23552 Lübeck, Germany
Abstract Users of hydro-meteorological data often face problems with collecting, handling and quality control of data from radar and raingauges. Current web technologies allow centralised storage, data management and integration of software tools. HydroNET and SCOUT tools have been integrated to produce accurate precipitation information and to present easy-to-understand interfaces to practitioners. The SCOUT software has been developed by hydro&meteo for obtaining calibrated precipitation information from raw radar data. HydroNET has been developed by HydroLogic with the aim of bringing meteorological data to the desktop of water managers and to support their daily work. Co-creation with users has led to HydroNET portal (www.hydronet.eu). This portal integrates the functionalities and supports water managers in assessing historical, current and forecasted precipitation events. The portal has been built using the Software as a Service (SaaS) paradigm. It is highly customisable and permits the user to configure its own interface, tools and warning levels.

Key words precipitation; raingauge; radar; RTC; DSS; web-service; SaaS; HydroNET; SCOUT

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 632-637.

Radar-based pluvial flood forecasting over urban areas: Redbridge case study
Li-Pen Wang¹, Nuno Simões^{1, 2}, Miguel Rico-Ramirez³,
Susana Ochoa¹, Joao Leitão⁴ & Čedo Maksimović¹

1 Department of Civil and Environmental Engineering, Imperial College London, Skempton Building,
South Kensington Campus, London SW7 2AZ, UK

[e-mail]

2 Department of Civil Engineering, University of Coimbra, Coimbra, Rua Luís Reis Santos, 3030-788 Coimbra, Portugal

3 Department of Civil Engineering, University of Bristol, UK

4 Laboratório Nacional de Engenharia Civil, Av. do Brasil 101, 1700-066 Lisboa, Portugal
Abstract 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 1D/1D dual drainage simulation scheme. A highly-urbanised catchment, Cranbrook (located in the London Borough of Redbridge), is employed for this case study to analyse the associated uncertainties. The aim of this work is to assess the impact of using rainfall forecasts with different spatial and temporal resolutions to forecast pluvial flooding over urban areas. Results show that promising performance in hydraulic forecasting is in general observed by using higher spatial and temporal resolution nowcasts as inputs; this implies the necessity of using advanced radar-based nowcasting techniques to improve the state-of-the-art pluvial flood forecasting over urban areas.

Key words nowcasting; flood forecasting; radar; rainfall; urban drainage

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 638-643.

A new FEH rainfall depth-duration-frequency model for hydrological applications
Elizabeth J. Stewart, David G. MORRIS, David A. JONES &
cecilia SVENSSON

Centre for Ecology & Hydrology, Wallingford, Oxfordshire OX10 8BB, UK

[e-mail]
Abstract Recent research funded by the Joint Environment Agency/Defra Flood and Coastal Risk Management R&D Programme has developed a new statistical model of point rainfall depth-duration-frequency (DDF) for the UK. The analysis made use of an extensive set of annual maximum rainfall depths for daily and recording raingauges across the UK. The new model will eventually replace the Flood Estimation Handbook (FEH) rainfall DDF model to provide estimates of rainfall depth for storm durations ranging from under 1 h to 8 days and return periods from 2 years to >10 000 years. The paper reports on current progress to generalise the new model so that it can be applied at any point, catchment or user-defined area, and potential links between the new model and hydrological applications of weather radar are highlighted.

Key words rainfall; depth-duration-frequency; Flood Estimation Handbook; radar rainfall; urban drainage

Weather Radar and Hydrology

(Proceedings of a symposium held in Exeter, UK, April 2011) (IAHS Publ. 351, 2012), 644-649.