Urban Flood Forecasting Now a Reality: CIWEM Urban Drainage Group Presentation

ICMLive & KickingBryony Crickmore Richard Allitt Associates LtdAlex Grist Richard Allitt Associates Ltd

Thursday 5th November 2015

ICMLive and Kicking 05/11/2015

Contents Introduction

Concept

Process

The Model

Data Streams

Examples

After the Alert

Summary


Overview

Richard Allitt Associates (RAA) has undertaken an offline trial of ICMLive (flood forecasting software) in partnership with Borough of Poole, Bournemouth Borough Council and Wessex Water.

The Bournemouth & Poole fully integrated models were used to run ‘real-time’ simulations and generate alerts to forewarn of predicted events


Process


Concept Aim of trial was to provide a ‘real-time’ model that generated forecasted alerts for

flooding from all sources and spill events

Use Met Office “Nowcast” and “Nimrod” data alongside data provided by Wessex Water

Need originates from pluvial flooding problems

Alerts would be set up that focussed upon predicted flooding and spill events


The Combined Model 394,000

Population

30,802 Nodes

30,702 Conduits

3 details 2D zones

3.9km of river reach

2D ponds


The Model

Aim of ‘real-time’ simulations = quick & accurate predictions

Quick AND Accurate model achieved by;1. Model Simplification2. Model Confidence


The Model - Confidence

Model confidence comes through comprehensive verification of the model prior to its use in ICMLive

Verification of the model helps to:- Minimise chance of genuine alerts not being sent

Both the Poole and Bournemouth models were fully verified for the foul/combined, surface water, fluvial and pluvial runoff so we had the necessary confidence in their performance


The Model - Confidence


The Model - Simplification

Faster simulations will:1. Save Resources2. Allow decisions to be made quicker3. Allow more informed decisions to be made


Model - Simplification

Objects•12,050 nodes

•39 outfalls

•12,096 pipes

•1 2D zone

Bournemouth



25 min

Target Time = < 10 minutes


The Model - Merging WaPUG Code of Practice states:-

Grouping a number of similar consecutive pipes together to a single pipe (merging);

WaPUG Code of Practice states:-Excluding small diameter pipes from the periphery of the system and inputting the flows to the next pipe downstream (pruning);

The Model - Pruning



Purple lines = Pruned links


The Model - Pruning



25 min

Target Time = < 10 minutes



25 minutes

Baseline

4 minutes

Pruned & Merged


The Model - Simplification Simplification was carried out to achieve a quick simulation time

Areas of interest were left unaltered and only the surrounding areas were simplified

The result of this simplification is that the run time was drastically reduced making them fit for purpose

Model was check after each stage of simplification to ensure that the confidence remained in the model


Data Streams Spatial data:

1. Met Office Nowcast (forecast)2. Met Office Nimrod (hindcast)

A script downloads from the FTP site every 10 minutes and then the ICMLive system automatically loads the data into the system every 10 minutes

Scalar data:1. Rain Gauges2. Flow Monitors


Frontal Rainfall Example

Nimrod

5 hours warning

Nowcast

02:14 – 29/10/2015

09:14 – 30/10/2015


Actions & AlertsAlert Definition List

Action List






Actions & Alerts

Action List


Example Outputs

Manholes predicted to flood are listed

The onset and the end time of the event included


Example Ouputs Results are displayed in the

operator client interface

Themes have been predefined in the manifest

Customized the theme

Radar rainfall has also been set up to be displayed


Storm Event 03/07/2015 1 in 100 year storm event hit Bournemouth on the evening of the 3rd of July

this year Localised event of short duration but caused a lot of damage with a

number of properties suffering from internal flooding

http://www.bournemouthecho.co.uk/news/13370923.Flash_flooding_and_spectacular_skies_as_Dorset_hit_by__megastorm_/?ref=trn


23:00


23:15


23:30


23:45


00:00


Forecast Rainfall (03/07)23:00 23:15 23:30

23:4500:00


Example – Lower Gardens Many of the sewers and drains surcharged in this area as well as river flooding

Were closed for several days due to overflowing sewers

http://www.bournemouthecho.co.uk/news/11327036.VIDEO__Bournemouth_s_Lower_Gardens_flooded_after_heavy_rain/


Example – Lower Gardens Series simulations run from 22:00 to 00:30

First simulation where relevant alerts issued = 23:30

Onset time of predicted flooding:

23:15 23:30 WarningFoul/Combined - 00:00 30 minutesStorm - 23:45 15 minutes


Example – FloodingAlerts generated from 23:30

simulation highlighted in greenReported/observed flooding cases for 03/07 storm from Bournemouth Borough Council

Predicted and known events in very similar locations


Example – Flooding

First simulation where relevant alerts issued = 23:30

Onset time of predicted flooding:- Range from 23:40 until 00:20- Warning time ranging from 10 to 50 minutes

597 flooding alerts were generated from the 23:30 simulation (356 alerts foul/combined)


This was a ‘thunderstorm’ one of the problems is that this rainfall is not ‘predicted’ well by the current Met Office Nowcast data.

This necessitates the need for a model to run as quickly as possible as the predicted rainfall lead time may only be 30 mins.

Example Flooding


The Model – ‘Parent/Child’ Recent software development was that of the ‘Parent/Child’ arrangement

Trigger alert generated

Poole ‘Child’ Model Triggered

Bournemouth ‘Child’ Model Triggered

‘Parent’ Model

Trigger alert not generated


After the Alert – Benefits

Local CouncilsAccurate prediction of flood;

1. locations2. depths3. extents4. Timings

Enables councils to prepare the catchment by;

1. readying flood response teams2. closing flood gates3. preparing sand bags4. warning the public


After the Alert - BenefitsWater CompaniesOperational benefits

Greater control over CSO spills

Reduce impacts by;1. emptying storm tanks in

advance 2. controlling pumping

stations 3. operating sluice gates


Summary

ICMLive enabled us to set up a fully integrated flood forecasting model for an urban area of 394,000 population

Used in conjunction with Bournemouth Borough Council, The Borough of Poole and Wessex Water

Alerts successfully generated from the model that forecasted flood and spill events

Forecast data still has short comings when predicting flood and spill events due to convective storms


Next Steps

Use of scalar data

Refining the alert & action lists

Bring it online!

Any Questions?@raa_ltd

Urban Flood Forecasting Now a Reality: CIWEM Urban Drainage Group Presentation

Engineering