Contribution of citizen science in

flood hazard assessmentBocar Sy, Corine Frischknecht, Hy Dao, David Consuegra, Gregory Giuliani

Yeumbeul Nord:

Area: 9km2

Total population: 168’379

Altitude: 0-20m

Several floods: 2005, 2009

Flooding causes: Natural and

anthropogenic

Where: Yeumbeul Nord, Dakar, Senegal

Dakar

Sea

This area is characterized:

Lack of catalogue of past

events

Poor coverage of

hydrometeorological data

No regular update of basic

data

Some issues with satellite

images (e.g frequency)

82 Neighbourhood

chiefs and 182

local

representatives

Local associations

and selected

people

Local associations

Training, rain

gauge fabrication,

data collection,

data on Facebook

Validation of land-

use map, mapping

with handled GPS

and mobile GIS

Training on map,

mapping on the

field, double

checking

Rainfall data acquisition, land-use mapping and investigation on

past flood events

Training, different target

groups, local languageHigher

quality data

Rainfall Land-use Flood events

daily

average

information

more detailed

and updated

depth

extent

How: Involvment of citizens

Daily average rainfall

0

5

10

15

20

25

30

35

40

45

TND DRS5 LDIAT NSEN MSY DBA Dakar Yoff

30.08.2016 06.09.2016 10.09.2016 11.09.2016 17.09.2016

Citizen rainfall data versus the nearest official station

(Dakar-Yoff), located 20 km from Yeumbeul Nord

Official station

.

Citizen gauges vs official station

Values are in the same range

with a variability less than 10 mm

(exception of 17Sept.)

Results

Extent

Neighbourhood chiefs vs

remote sensing

Some differences in spatial

distribution

Remote sensing 0.72 km2 and

neighbourhood chiefs 0.90 km2

an increase of 25%

Neighbourhood chiefs

2009 event: depth varies from

0.2 m to 1m

Depth

Results

Citizenscience

Ground

dataCitizenscience

Scenario

Basic

data

Key flood

hazard

parameters

Scenario

Basic

data

Key flood

hazard

parameters

Past flood events

having affected the

area

Land-use elements

potentially influencing

flood magnitude

Rainfall intensity

An alternative approach

for areas with scarce data

and insufficient financial

resources

New insights on

Thanks