Floods and Landslides experiments

 

1) Norway Case Study - Preventing floods and landslides

The researchers in Norway tested flood retention and the impact of vegetation on river bank stability in the Morsa Catchment. They modelled the effect of different sized retention dams in forest areas (upstream agricultural fields) and the root strength of river bank vegetation.

Norway flooding
Preventing floods and landslides

Final Results

Water retention ponds

  • The flood peak is most likely lowered by the inclusion of a retention area in the catchment. The retention area has a large impact on decreasing soil erosion on the down-slope agricultural fields.  It captures and diverts surface runoff, resulting in less sheet and especially gully erosion on the agricultural land.
  • Although the number of floods was not quantified during the experiment, according to the statements of the farmers, the flooding over
    the agricultural land is reduced from 2-3 times a year to once every second year (reduction in local flooding). 
   Norway RA Figure2
  Example of the modelling results for the area without and with implemented retention pond 

Further details about this experiment can be found in the fact sheet HERE (NOand in the project report HERE

Bank stability 

  • The grass and shrub plots showed similar dynamics both in groundwater level and soil water content fluctuation, while clear differences were observed in hydrological responses within the plot containing trees. The trends observed in soil water content variation corresponded to the groundwater level fluctuations. The differences can be explained by different root depths and subsequent root water uptake.
  • Soil-root strength changes with time. In all three plots, higher values of shear strength were observed during late spring and summer. This trend stems from two factors: intensity of the vegetation growth (higher root density) and lower soil moisture content. Variation in modelled slope stability corresponds to variation in groundwater levels and stream water levels.   The probability of riverbank failure was higher during spring and early autumn, and lower during the summer. The tree plot was the most stable and shows the highest capacity to accommodate potential shear stress.
Changes in average shear strength with time and with depth, for the three plots   Norway BZ Figure3
Changes in average shear strength with time and with
depth, for the three plots
  Frequency of Fs for all simulated scenarios, for min and max slope angles. Stability classes: red – unstable slope; yellow – conditional stability; green – stable slope

Further details about this experiment can be found in the fact sheet HERE (NOand in the project report HERE.

For more information about this experiment, please contact Jannes StolteThis email address is being protected from spambots. You need JavaScript enabled to view it.

 

2) Slovakia Case Study - Mitigating muddy floods and soil erosion

The researchers in Slovakia conducted three eperiments 1) tested the effect of rainfall intensity, soil moisture and vegetation cover on generation of overland flow and sediment transport; 2) measurements of gully erosion; and 3) measurements of sediment loads and bed sediments in a small water reservoir.

muddyfloods gulleyerosion
                                                               Mitigating muddy floods and gully erosion

Final results

 Experiment  Results 
1. Generation of surface runoff  
  • High dependency on the type of soil cover, crop management techniques used, and the stage of vegetation growth on the volume of surface runoff,
  • bare soil together with high initial soil moisture (above 40%) had the most significant impact on the amount of surface runoff,
  • erosion modelling confirmed a good protective effect of winter wheat, which could be planted even on steeper slopes, with no need to plant an excessive number of protective vegetation strips,
  • the simulations with a 100-year rainfall revealed, that when compared to the bare soil, a 42% decrease of surface runoff volume was estimated when the area was used for maize production, and as much as a 90% decrease when used for winter crop production. 
 CropsResults
 2. Changes in erosion gully
  • Analysis of historical maps identified changes in the position of the gully erosion between the individual years, while the bottom part stayed relatively stable
  • For a detailed analysis of gully erosion, the experiments focused on the assessment of changes in the gully rills volume and selected parameters using a terrestrial laser scanner, UAV technology and GNSS. The measurements show that despite the use of small wooden check dams, the erosion processes are still ongoing
  • Comparison between 2014 and 2015 showed the gully volume had increased by more than 10 %. Between 2015 and 2016 the volume increased by almost 80 m3, which represents an 8% increase
  • Measurements suggest that the geometry of the erosion gully near the wood check dams is somewhat stable. The gully is continuously observed and monitored
  • In two of the existing check dams, an increase in the longitudinal slope was recorded, which was caused by deposits of eroded soil particles.
     results 2    
 3. Changes in sediment loads
  • Over five years, 10.694 m3 of bottom sediments accumulated in the Svacenický Creek reservoir.  Meanwhile, during the same time period, 179m3 of soil on the area above 1,693m2 was eroded.  Results confirmed ideas about ongoing sedimentation processes in Svacenický creek.     
  • Management practices caused significant differences between runoff and the amount of soil loss in the Svacenický creek catchment.
  • In the case of different land management strategies, the most intensive erosion processes were detected on the fallow land cover type as opposed to the winter wheat, where the effect of the net erosion rapidly decreased in the catchment                  
results 3

 

Further details about the experiment on the generation of runoff can be found in the fact sheet HERE(SK), changes in erosion gully fact sheet HERE (SK) and changes in sediment loads HERE (SK) and in the project report HERE.

Scientific Articles

Michaela Danáčová, Radovan Nosko, Roman Výleta, Beata Randusová, Ján Szolgay (2015) Possibilities of estimating the gully erosion changes on the Myjava Basin Published in: ACTA HYDROLOGICA SLOVACA Ročník 16, Tematické číslo 1, 2015, 167 - 175

Korbeľová, Lenka, and Silvia Kohnová (2017) Methods for Improvement of the Ecosystem Services of Soil by Sustainable Land Management in the Myjava River Basin Published in: Slovak Journal of Civil Engineering 25, no. 1, 2017, 29-36  https://doi.org/10.1515/sjce-2017-0005

Čistý, M., Čelár, Ľ., Minarič, P. (2015) Conversion Between Soil Texture Classification Systems Using the Random Forest Algorithm, Air, Soil and Water Research. Published in: Air, Soil and Water Research. Volume 8, Pages 67-75, ISSN 1178-6221 http://www.la-press.com/conversion-between-soil-texture-classification-systems-using-the-rando-article-a5217

For more information about this experiment, please contact Ján Szolgay  This email address is being protected from spambots. You need JavaScript enabled to view it.