TY - JOUR
T1 - Flood risk reduction by parallel flood defences – Case-study of a coastal multifunctional flood protection zone
AU - Marijnissen, Richard J.C.
AU - Kok, Matthijs
AU - Kroeze, Carolien
AU - van Loon-Steensma, Jantsje M.
PY - 2021
Y1 - 2021
N2 - In this paper the safety of a double-dike system (or twin dikes) is assessed. Such a system consist of two parallel lines of flood defences. During storms the combined strength of the parallel flood defences must prevent flooding of the hinterland. A culvert can be implemented for the tidal exchange of sea water to enable new land-uses in the area between the dikes such as aquaculture, saline agriculture, salt marsh restoration and clay extraction. We develop a general framework for assessing the safety of such double dike systems and apply a simplified version to the Double Dike between Eemshaven and Delfzijl (The Netherlands) to test this method. In doing so, we aim to quantify the flood protection benefits of parallel flood defenses and enable their use in multifunctional flood protection strategies. Within the framework the transmission of hydraulic loads by the seaward dike to the landward dike in the case-study was described by overtopping, overflow and erosion of the outer slope, alongside discharge through the culvert in the event of a non-closure. For the subset of coastal double dike systems with a tall seaward dike (as in the case-study), the results show only a negligible improvement in flood protection compared to a single dike system. With the addition of a culvert in the first dike, flood risk will only be reduced by the second landward dike if its height is sufficient to retain water in the event of a non-closure during common storm events. These double dike systems are implemented for potential uses of the inter-dike zone, e.g. for nature restoration, rather than as a measure to primarily improve flood protection.
AB - In this paper the safety of a double-dike system (or twin dikes) is assessed. Such a system consist of two parallel lines of flood defences. During storms the combined strength of the parallel flood defences must prevent flooding of the hinterland. A culvert can be implemented for the tidal exchange of sea water to enable new land-uses in the area between the dikes such as aquaculture, saline agriculture, salt marsh restoration and clay extraction. We develop a general framework for assessing the safety of such double dike systems and apply a simplified version to the Double Dike between Eemshaven and Delfzijl (The Netherlands) to test this method. In doing so, we aim to quantify the flood protection benefits of parallel flood defenses and enable their use in multifunctional flood protection strategies. Within the framework the transmission of hydraulic loads by the seaward dike to the landward dike in the case-study was described by overtopping, overflow and erosion of the outer slope, alongside discharge through the culvert in the event of a non-closure. For the subset of coastal double dike systems with a tall seaward dike (as in the case-study), the results show only a negligible improvement in flood protection compared to a single dike system. With the addition of a culvert in the first dike, flood risk will only be reduced by the second landward dike if its height is sufficient to retain water in the event of a non-closure during common storm events. These double dike systems are implemented for potential uses of the inter-dike zone, e.g. for nature restoration, rather than as a measure to primarily improve flood protection.
KW - Double dike
KW - Flood risk
KW - Multifunctional flood defences
KW - Nature-based flood defences
UR - http://www.scopus.com/inward/record.url?scp=85107076644&partnerID=8YFLogxK
U2 - 10.1016/j.coastaleng.2021.103903
DO - 10.1016/j.coastaleng.2021.103903
M3 - Article
AN - SCOPUS:85107076644
SN - 0378-3839
VL - 167
SP - 1
EP - 18
JO - Coastal Engineering
JF - Coastal Engineering
M1 - 103903
ER -