Managers of flood defences perform safety assessments of to check whether their flood defences satisfies the safety norm. They use the DUROS+ model for the dune safety assessments; this model uses hydraulic conditions and grain size as input variables and accounts for uncertainties induration and accuracy. These hydraulic conditions are calculated to execute the safety assessment without required knowledge about probabilistic calculations, and are based on probabilistic calculations. 
 
The impact of Non-Water-Retaining

objects

(NWO)

on

dune

safety

is

currently

not

included

in

the

Duros+

model

(model

for

dune

safety

assessments

)

.

This

study

aims

to

include

the

impact

of

NWO's

on

dune

safety

in

the

probabilistic

calculations

for

the

determination

of

the

input

parameters

in

the

Duros+

model.

The

impact

of

NWO's

on

dune

safety

in

this

study

is

based

on

calculation

rules

developed

by

Deltares

and

Arcadis.