Technical report erosion resistance of grassland as dike covering

Technical report erosion resistance of grassland as dike covering

Verheij, H.J.
Kruse, G.A.M.
Niemeijer, J.H.
Sprangers, J.T.C.M.
De Smidt, J.T.
Wondergem, P.J.M.

Rijkswaterstaat

TAW/ENW

1997-11-28

Old dikes are usually still constructed entirely from clay and since 1953 many much heavier dikes have been made from a core of sand with a covering. This construction puts heavier requirements on the covering, as it also does for grassland on a clay layer. These and other developments have led to the need for more insight into the strength of grassland as a dike covering and into the possibilities of managing it better. Regular maintenance is essential for grass coverings and furthermore they are relatively sensitive in their early years to damage; even somewhat older grass coverings sometimes show signs of unexpected damage. They require expenditure to put right and cause doubts about their strength under extreme circumstances. In addition, the Flood Defences Act requires an evaluation every five years of the existing primary flood water defences, of which the dike coverings form an important part. Dike managers have an inclination to put a hard covering on a dike because there is so little insight into the strength of grass coverings, thereby contributing to the reduction of herbage-rich grasslands. As a result, the other functions of dikes, such as the preservation of environment, landscape and culture-history values (abbreviated in Dutch as LNC-values), recreation and agriculture get less attention. Because dikes play a water defensive role before everything, other functions can only be considered if the required erosion resistance of the covering is sufficiently durable. Safety against water is the primary goal, for river, sea and lake dikes. This study has also been aimed at increasing insight into the strength of grassland as a dike covering and on measures that can increase the desired strength.

grass
dikes
levees
wave-structure interaction

TPG130510

http://resolver.tudelft.nl/uuid:446b0289-dad6-4c87-b8cd-bb81128a5770

Rijkswaterstaat, DWW

English translation of a TAW guideline

Hydraulic Engineering Reports

report

© 1997 Rijkswaterstaat