Galton boards: steel balls travel down and land in 1 of 4columnswithateachjunc8ona50%chanceofballgoingle=orright. Galton boards randomly determine: (i) rainfall amount(columns: 1s, 2s, 4s, or 9s) and (ii) rainfall loca8on (columns:lake/reservoir, moor & reservoir, moor, or no rainfall).ProbabilityasymmetricGaltonboard:(3,7,5,1)/16.Planview:

Wetropolis:modelsforeduca8on&water-managementoffloodsanddroughtsOnnoBokhove1,TomKent1,HenkdePoot2andWoutZweers3

1SchoolofMathema8cs,UniversityofLeeds,Leeds,UK;2Nobis&3Wowlab,Enschede,TheNetherlands

“Wetropolis:makingtangible,interac8vemodelsforeduca8on&policy”isanEFRORDconsor8um(EUfundforregionaldevelopment),ledbyNobis,DrHenkdePoot,henkdepoot@nobis.pro References

Educa8on&water-managementMathema8csofextremerainfall/flooddemonstrator

Wetropolis interac8ve flood demonstrator is based on amathema8cal design and visualises how extreme rainfall events cancauseextremeriver-floodeventsinadynamic,conceptualandscaledtable-topset-up.GaltonboardsareusedtomodeldifferentrainfallscenariosoverthecourseofaWetropolisday(wd=10seconds)andextremefloodinginacitybyrainfallonthecurrentandpreviousdays,asintherealworld[1].

Overview,modelleda=erLeeds’BoxingDayflood2015(1:300yrreturn-periodevent):•  1:100 sloped river bed;Wetropolis day 10s; upstream inflow;with

canal,reservoir/lake&porousgroundwatermoordrainingintoriver;•  chance of rare flood event in city a=er 90% rainfall (9s/wd) is

(1/16)x(7/16)=7/256witha(256/7)x10s=6:06minreturnperiod.

Wetropolis isdesigned toflood ( r i g h t ) u n d e rextreme rainfall (9s/wd)in moor & reservoir; twoconsecu8ve wd ’ s o fextremerainfall leadtoachance of (7/256)2 <1%;cf.Boxing-Dayflood2015,see; hkps://youtube.com/watch?v=N4Sp5gHXcz4

Droughts:tovisualisedroughtforthe1/16throuteofadryday,weusetheoutcomeofthefirstGaltonboard(notusedwithoutrainfall)a=er2pinswith(3,1)/4probability.Forthe1/4-case,weenforcedroughtfor4days,visualisedbyadrinkwaterpipefromthemoorfallingdry:nowatersupply!Newproba-bili8esthenadjustto:(12,28,20,3,4)/67forrainfallinreservoir,moor&reser-voir,moor,norainonsingleday&norainfor4days.Droughtreturnperiod:67x10s=11:10min.Newfloodingreturnperiod:(16x67/28)x10s=6:23min.

Modulardesign:wearecurrentlymakingaWetropolisNFMdemonstratorwith•  par8cipant-built

leakydamsinoasis-landscape;and,

•  river-bedinsertsofdifferentroughness(“trees,cement,gravel”).

NFM=NaturalFloodManagement.

PromoteacDvethinkingaboutdifferentscenariosofflood/droughtmi8ga-8on:Wetropolisisusefulprecursorincrea8on[2]ofwater-management

solu8ons;alsoenhancesci8zens’par8cipa8on.

Wetropolisledtoflood-excess-volumebasedcost-

effec8venessanalysis,e.g.,RiverBragueflood

2015,France[3]: