My last post explored the mud flats bordering the North Sea in northern Germany, where we found conflicting methods applied to control and protect the levee system. This post investigates more aggressive measures implemented at the mouth of the Eider River. We will briefly look at the Eidersperrwerk, a gate system designed to control both storm surge incursion up the Eider, and river outflow
We will focus on the seaward mud flats in this post. Let’s take a look at the south side of the river first (upper-right of Fig. 1).
Comparing Fig. 1 to Figs. 2 and 5-8, we can see the effects of years (probably decades), during which interval the northern margin of the river mouth filled with sediment and grass was established (Fig. 5). Subsequently, it seems that erosion removed some of this soil and grass (Fig. 6). Meanwhile, storms have been slowly wearing away the boulders armoring the base of the levee (Fig. 8) and a semipermanent fair-weather berm was constructed (compare Figs. 1 and 7).
In summary, something appears to have changed in the dynamic environment around the mouth of the Eider. It should come as no surprise that constructing a gate system and cutting off a major sediment supply for at least half the time had dramatic effects on the nearshore. Mud flats are very sensitive to sediment supply, and it could have been either reduced alongshore transport from the north, or the almost-complete denial of rive-borne mud that led to the current situation.
Some scientists propose that storminess varies on many scales, from decadal to millennial as climate fluctuates…