Project name: Heidlandgraben, Heykenauweg, Hamburgo, Germany

Products: Secumat® 601 G4 | Secutex® 301 GRK 5 C

                              Fig. 1: Cutting of Secumat® in situ                          Fig. 2: „Interlocking“ of the topsoil with the artificial root
                                                                                                                                network of Secumat® on the slope

Challenge

While expanding the surface drainage of an industrial area in Hamburg-Hamburg, the Heidlandgraben was expanded. The cross-section of the drainage channel had to b given a large volume in the confined space between the plots of land and thus be able to hold more capacty. For this reason, it was necessary to make the slopes relatively steep. The subgrade formed a sandy subsoil, on which the topsoil for the greening requires additional support against surface-parallel erosion phenomena.

In spring, Northern Germany often experiences heavy rainfall, which also in Hamburg repeatedly leads to severe erorion phenomena (e.g. groover or surface erosion) on newly formed slopes. As the construction of the new cross-section of the Heidlandgraben took place directly after the high-risk winter period, more frequant erodion damage was to be expected.

Fig. 3 3: Erosion-protected Heidlandgraben after completion with Secumat®.

Solution

To protect the Heidlandgraben against erosion damage, the client decided to use the Naue® erosion control system. A permanent erosion control mat with an extruded polypropylene monofilament core from Secumat® product group was used.

The erosion control mat was cut to size on site to the appropiate length for the slope (plus anchor trench). Due to its low weight, the material was intalled by hand. The backfilling was carrie out using a long arm excavator from the accessible side of the channel. Armourstones were placed in the bottom of the channel. To effectively prevent the sandy subsoil from beign washed out through the coarse backsill even in the event of a substantial rise in the water level, a Secutex® separatio and filter nonwoven was installed on the subgrade in advance.

The artificial UV-stabilised root network of Secumat® products provided better support for the topsoil on the steeply formed slope flanks of the trench -  especially during the construction phase, but also permanently after greening hand taken place.

The positive effect of Secumat® was already evident during the construction phase. During heavy rainfall events, the difference between embankment areas already finished with Secumat® and topsoil and the areas not yet worked on became clear. On te slopes that had already been profiled but not yet covered with Secumat® and new topsoil, deep erosion grooves formed in some cases due to surface water collecting and running off, while the areas newly constructed with Secumat® did not show any significant erosion.

After completing the construction measure in 2007, the vegetation was able to establish itself on the embankments within a very short time. Even today, the slope flankfs of the Heidlandgraben are very well protected by the installed Secumat® product and show no erosion damage.