Investigating the Erosion Resistance of Different Vegetated Surfaces for Ecological Enhancement of Sea Dikes

Abstract

Dense grass covers are generally recommended for surface protection of sea dikes against mild and moderate hydraulic loads. The standard seeding mixtures were composed to meet the technical requirements and ensure dike safety. These mixtures are, however, limited in their species diversity. In the present study, four differently vegetated surfaces were tested regarding their erosion resistance against wave impacts and overflow. The test vegetations ranged from a species-poor grass-dominated reference mixture to species-rich herb-dominated mixtures. Two vegetations were reinforced with a three-dimensional geogrid. For the unreinforced vegetations, the erosion rate due to wave impacts decreased exponentially with increasing root density and root length density. The geogrid reinforcements functioned as additional protection when the upper vegetation layer was eroded and led to slightly decreasing erosion rate with depth. In overflow simulations, the relatively densely-vegetated grass-dominated mixture experienced least erosion. Erosion was mainly initiated at bare spots emphasizing the major role of a closed vegetation cover and dike maintenance. The present results give new insights into erosion patterns of unreinforced and reinforced vegetated dike covers and the relation between vegetation parameters and hydraulic resistance to wave impacts and overflow.

The Effect Of Geometrical Transitions On The Wave Overtopping Load

“…The coefficients have the dimensions 29.4 kg/m 10/3 , 443 N/m 2 , 11.8 kg/m 10/3 and 108 N/m 2 . The increase in load with increasing height was also found in previous studies (Scheres & Schüttrumpf, 2020;Stanczak, 2008).…”

The four components to combine flood protection with other functions

“…A similar concept in which the dike's ecological value is enhanced by flowers or herbs on its outer cover, is another example. The erosion-resistance of the dike cover is primarily governed by the root density and the overall root depth (Scheres & Schüttrumpf, 2020;Vannoppen, Poesen, Peeters, De Baets, & Vandevoorde, 2016). Introducing additional vegetation species to improve the ecological value of the dike therefore has a direct influence on the dike design.…”

Numerical Modeling for the Effect of Soil Type on Stability of Embankment

“…Dikes are widely used to save various types of lands and avoid the danger of overtopping failure [2,3], drinking and irrigation, energy production and recreation purposes [4] as well as support power generation [5]. Overtopping failure, which occurs due to the transition of overtopping wave into the downstream slope, is considered the main cause of dike's failure [6,7]. The dike's breach failure is dependent on different geotechnical and hydraulic parameters, such as excess rainfall, upstream slope collapse, settlement of the dike crest, inadequate design and construction of the spillway, and global warning [8].…”