  Understanding the response of estuaries to sea-level rise is crucial in
developing a suitable mitigation and climate change adaptation strategy. This
study investigates the impacts of rising sea levels on salinity intrusion in
salt-wedge estuaries. The sea-level rise impacts are assessed in idealized
estuaries using simple expressions derived from a two-layer hydraulic theory,
and in the Neretva River Estuary in Croatia using a two-layer time-dependent
model. The assessment is based on three indicators - the salt-wedge intrusion
length, the seawater volume, and the river inflows needed to restore the
baseline intrusion. The potential SLR was found to increase all three
considered indicators. Theoretical analysis in idealized estuaries suggests
that shallower estuaries are more sensitive to SLR. Numerical results for the
Neretva River Estuary showed that SLR may increase salt-wedge intrusion length,
volume, and corrective river inflow. However, the results are highly non-linear
because of the channel geometry, especially for lower river inflows. A
theoretical assessment of channel bed slope impacts on limiting a potential
intrusion is therefore additionally discussed. This findings emphasize the need
to use several different indicators when assessing SLR impacts.
