LGA Institut für Umweltgeologie und Altlasten GmbH

Runoff modeling – Valuable forecasting tool for upcoming heavy rainfall events

Posted on 12 June 2023.

Repeated heavy precipitation in 2017 and 2019 led to debris flows in the community of Kauerndorf, which buried the B289 federal road. As a precautionary measure to prevent further debris flows, the construction of an erosion protection construction was therefore planned, which should reduce the catchment area of future heavy precipitation. We were commissioned to prognostically verify the effectiveness of the planned structure. For this purpose, runoff modeling was generated based on the Digital Elevation Model (DTM) with 1-m resolution.

In concrete terms, when calculating a runoff model, sinks without runoff are first eliminated in the DTM (= filled). These are flowed through in reality and would distort the model without correction (= filling). Then, the flow direction of each cell, or square meter, is determined based on the slope. In this way, it is determined into which neighboring cell a drop of water theoretically flows in the cell under consideration. Based on the flow direction, the runoff per cell is finally accumulated. Cells with a high runoff accumulation value are areas where surface runoff is concentrated.

Flow direction and number of cells flowing into each cell
(Source: https://desktop.arcgis.com/de/arcmap/latest/tools/spatial-analyst-toolbox/how-flow-accumulation-works.htm)

In order to verify the effectiveness of the planned erosion protection construction, project manager Thomas Struller set up an investigation concept in which, in a first step, the real runoff conditions are modeled and validated or calibrated on the basis of terrain surveys. In a second step, the terrain surface is manipulated in the model to represent the geometry of the planned construction. Remodeling the runoff conditions with the manipulated surface then shows the runoff after the construction has been built. The difference between the two models can be used to derive the effectiveness of the construction.

According to Simon Landgraf, who performed the modeling and terrain survey, there was no need to calibrate the model. Already the first calculation presented runoff lines that exactly matched the reports of local residents and the event sketches of the debris flows. This high level of agreement is consistent with experience from other projects, in which torrents and mudslides that had already occurred could be reconstructed with meter accuracy by the runoff modeling and thus the source or cause of the event could be determined retrospectively.

Modeled surface runoff

The second model with incorporated erosion protection construction clearly showed that the runoff formation in the upper slope can be reduced by the construction. There is hardly any surface runoff in this area, which in turn greatly relieves the erosion channel in the lower slope. The effectiveness of the erosion protection construction could thus be prognostically tested and proven.

Result of runoff modeling with erosion protection construction

Rockfall protection fence and then what? About the need for regular construction inspections

Posted on 20 April 2023.

High demands are placed on safety constructions (SiBW) against falling rocks and boulders with regard to structural safety, serviceability and durability. It is often forgotten that the construction of rockfall protection fences, meshes, rock nails, shotcrete and the like does not per se provide protection for decades. To reliably fulfill their function, regular inspection and, if necessary, maintenance (servicing) and repair (overhaul) of the SiBW are required.

For inspections, a distinction is made between initial recording, visual inspection, checking, testing and special checking. During the initial recording, the structure is inspected and all data relevant to the construction are recorded on a form. The annual visual inspection is used to check for any events that may have occurred and/or major damage (possibly affecting the serviceability of the SiBW). The visual inspection also serves to check the SiBW for vegetation that would hinder a reliable inspection of the construction in the following year, so that an clearing can be arranged in good time. If, in the opinion of the expert, the serviceability of the SiBW is impaired or an incident is reported, a special check of the SiBW is recommended. The regular inspection in the 5-year cycle replaces the visual inspection in the corresponding year and includes a manual inspection specific to the construction. The inspection in the 15-year cycle replaces visual inspection or checking in the corresponding year. Like the checking, the testing is carried out close to the hand and specific to the construction. In addition, the environment of the SiBW is checked for relevant changes to ensure the continued suitability and serviceability of the SiBW.

Inspection at an old safety construction

The inspections of the past months show the usefulness and necessity of initial recordings and periodical inspections. This year again, numerous “minor” defects were found, ranging from incorrectly installed wire rope clamps and missing components to incompletely filled boreholes with exposed anchors, thus negatively affecting the serviceability of the SiBW. As far as the defects are not due to external influence (missing component, theft, vandalism), experience has shown that they are usually remedied by the construction company at no cost, especially if the defect is claimed within the warranty period.

Exposed anchor

Other defects, in turn, included severe corrosion on constructions as well as uninspected self-built constructions on rock sections above residential buildings that are at risk of falling. Here, the defects cannot be remedied with simple steps, but the inspection should still not be avoided. After all, the inspection of the condition of a SiBW is closely linked to the question of insurance and liability in the event of personal injury and property damage.

Old metal cramps and rock nails, checking via rappelling

Feel free to contact us when:

• There are SiBW of unknown age and origin on your parcels of land
• You are a SiBW owner and have not had any inspections carried out yet
• You do not know for sure what condition your SiBW is in
• You wish to ensure that any claims for defects can be asserted before the expiry of the warranty period (in the case of buildings in accordance with VOB/B §13 Para. 4 four years after acceptance of the building)
• You want a tabular record and spatial location of your SiBW
• You wish to have an inspection plan for your SiBW for your long term planning
• You wish to be advised in any other way on SiBW and inspections

Foundation stone laid for Cube One of UTN (University of Technology Nuremberg)

Posted on 21 November 2022.

Since the purchase of the land by the State of Bavaria, the LGA Institut für Umweltgeologie und Altlasten GmbH has accompanied the formation of the UTN – the new Technical University of Nuremberg.

On November 18, 2022, Prime Minister Dr. Markus Söder then laid together with the Science Minister Markus Blume, Construction Minister Christian Bernreiter, the founding president at Nuremberg University of Technology, Prof. Dr. Dr. h.c. mult. Hans Jürgen Prömel, and the Mayor of the City of Nuremberg, Marcus König, the foundation stone for the first building on the campus – Cube One.

The time capsule with photos of the undeveloped area, a streetcar model, a building model and a USB stick with programming code is walled in (from left: Marcus König, Christian Bernreiter, Markus Söder, Markus Blume and Hans Jürgen Prömel)

The foundation stone is laid

The LGA Institut für Umweltgeologie und Altlasten GmbH contributed to the quick realization of the building project with the investigation and remediation of contaminated sites, with the supervision of the site clearance and with the preparation of a contaminated site and subsoil expertise (in cooperation with LGA Baugrund GmbH). Even the radon concentrations in the subsoil were measured by the LGA Institut für Umweltgeologie und Altlasten GmbH investigation department and the radon activity concentrations for the future building were estimated – harmless.

The LGA Institut für Umweltgeologie und Altlasten GmbH was also allowed to participate in the structural planning and in the framework planning for the UTN. Their greatest concern, to prevent senseless soil disposal with gigantic emissions of CO2 and waste of diesel fuel through intelligent soil management, found its way into the planning and was laid down in a progressive soil management concept together with the environmental protection office of the city of Nuremberg. For the construction of Cube One, therefore, only a few hundred tons of soil from a fuel spill had to be disposed of via biological cleaning – a great success for the environment!

New Mantelverordnung: introduction of EBV and adaptation of BBodSchV, DepV and GewAbfV

Posted on 04 October 2022

In July 2021, the legislature published the new Mantelverordnung (“Regulation on the Introduction of a Substitute Construction Materials Regulation, on the Revision of the Federal Soil Protection and Contaminated Sites Regulation and on the Amendment of the Landfill Ordinance and the Commercial Waste Ordinance”).

Classification of mineral waste

Substitute Construction Materials Ordinance (EBV)

The most important item is the introduction of the Substitute Building Materials Ordinance (EBV), which for the first time sets out nationwide and legally binding requirements for the production and use of mineral substitute building materials (including recycled building materials from construction and demolition waste, soil and dredged material, gravel for railway tracks). The EBV thus replaces, among others, the LAGA M20 leaflet.

Further information on the new regulations can be found here.

To give you an overview of the most important changes and help you prepare in good time, we have produced a brochure that you can download here:

Brochure on the New Mantelverordnung (German)

3D laser scanner measures and visualizes rock cellar in road embankment

Posted on May 10, 2022.

Determining the exact position of rock cellars or caves in relation to the ground surface requires precise surveying techniques. The smallest angular errors can “warp” the entire model and cause several meters of positional deviation above a certain corridor length, which is an unacceptable inaccuracy, especially for questions concerning building and traffic infrastructure.

3D scan of rock cellars under a building

However, the all-clear was given for the recently inspected basements. Besides a few structures in need of monitoring, the basements were mostly in good condition. The monitoring program is used to determine whether the monitored structures need to be rehabilitated or technically secured in the long term if their condition deteriorates.

Successful participation in various round robin tests

Posted on 07 March 2022.

The quality of sampling determines the accuracy of expert statements. Errors made here can no longer be cured in the subsequent steps.

Round robin test on explosive residues in soil     The Federal Environment Agency had invited engineering companies to this round robin test in Kempten. A plot of land contaminated by explosives was to be representatively sampled according to the rules of the “art of contaminated sites” (area composite sample of topsoil, effect pathway soil – man). Dr. Kunibert Eberlein and Simon Landgraf from our company were represented.

Sampling from an excavator shovel

Comparative measurement of groundwater sampling from a measuring point
In cooperation with four other offices or laboratories, we organized a comparative measurement at a groundwater measuring point. The analysis results (5 samples each for heavy metals and further inorganic parameters, 10 samples for LHKW), were comprehensively statistically evaluated. Fabian Ziegler, Hendrik Belz and Gerold Neumann participated from our office.

The results of the round robin tests on explosives residues are still pending.
The round robin tests for sampling at accessible and non-accessible excavations will be presented on 30.06.2022 within the framework of the GAB’s contaminated site symposium.
The statistical evaluation of the groundwater sampling was carried out by AIR – Analytik Institut Rietzler GmbH using the round robin evaluation software A45 from AQS Baden-Württemberg. In addition to the standard deviation of the on-site parameters, the zu-scores were determined for the individual samplers for the investigated organic and inorganic parameters. The results were made available to all test participants in a final report.