**10. References**

304 Soil Erosion Studies

*Vmax*=1.38×10-2 m/d

*Vmáx*=7.55×10-3 m/d

(a) Day 17 of filling

Fig. 22. Velocity vectors (magnitude) for two different time intervals during rapid filling and

(b) Day 44 of drawdown

The main conclusions and recommendations derived from this chapter are the following: If internal erosion caused by water flow or seepage through earth dams, levees, and other earth structures that contain water is not detected in time and if corrective actions are not taken to stop or control such erosion, the consequences may be a complete

 The process of soil erosion might occur through the mass of the earth structure or through its foundation. The initiation of this process usually starts at the exit point of

 The main factors that affect the erosion phenomenon are: a) the erodibility of the soil; b) the water velocity inside the soil mass; c) geometry of the earth structure. The erodibility of the soil depends on several factors, such as water content, plasticity index, undrained shear strength, mean grain size, percent passing #200, soil clay minerals, soil

 The seepage forces that affect the erosion problem are related to the hydraulic gradient that exists in the soil mass. This gradient might be computed and analyzed through the graphical flow net method or through one of the numerical methods that exist in the literature. Several procedures and practical recommendations were presented for preventing damages due to soil erosion. Among those are: a) Obtain the best selection of available construction materials; b) Control the homogeneity of the materials during the construction process; c) Use transition zones between the coarse and fine materials; d) Use properly designed filters and drains for all earth facilities exposed to damaging

 The erodibility of soils might be analyzed through laboratory and field tests. Some of the most common of these tests were mentioned in this chapter, particularly the ones

the seepage and retrogressive erosion results in the formation of a "pipe".

dispersion ratio, water salinity, soil pH and water pH, among other factors.

actions of water in their foundations or around the impervious core.

related to the identification of dispersive soils.

drawdown (exaggerated scale) (Lopez-Acosta et al., 2010)

**9. Conclusions and recommendations** 

failure of that structure.

*V*=1.23×10-2 m/d

*V*=1.19×10-2 m/d

*V*=3.54×10-3 m/d


**15** 

*1Germany 2Czech Republic* 

**Lake Mladotice in the Western Czech Republic –** 

Landscape changes are distinguished into those generated by natural processes and those caused or triggered by human activity (Barsch et al. 1993; Jansky & Urbanova 1994; Favis-Mortlock et al. 1997; Bork et al. 1998; Voelkel 2005; Bičik & Kabrda 2007; Bičik & Jeleček 2009). The geoarchives do not reveal which of these factors ultimately caused greater soil erosion. Improved dating techniques are necessary to increase the temporal resolution of the sediment records which have clearly increased the level of knowledge in recent years (e.g.

When examining sediment archives from recent times, we may have the opportunity to identify the factors controlling sediment formation in much more detail (e.g. Junge et al. 2005). This was the case with the natural "experimental setup" at Lake Mladotice (western Czech Republic), where it was possible to analyse a sediment archive dating back to 1872. Since the onset of lake sedimentation, rainfall and runoff have been recorded (in some cases continuously) at monitoring stations located in the surrounding area of the catchment area

Air photos from several decades document pre- and post-communist land use changes in the lake's drainage basin. Furthermore, records exist of fertiliser programmes affecting sediments and hydrochemism. Because of the change in land use, increased soil erosion and a rise in the sedimentation rate were expected. Against this background, our investigations into the lake sediments and the drainage area of Lake Mladotice aim to address the

1. To what extent has land use changed in the drainage basin of Lake Mladotice since 1872? 2. Has the magnitude or frequency of the rainfall runoff events changed since 1872? 3. To what extent is the sediment record a product of the rainfall runoff events or the

**1. Introduction** 

Geyh 2005, Kadlec et al. 2009).

following questions:

of the lake (Schulte 2007, Schulte et al. 2007).

change in land use in the drainage basin?

**Sediments as a Geoarchive for Flood** 

**Events and Pre- to Postcommunist** 

**Change in Land Use since 1872** 

*2Department of Physical Geography and Geoecology,* 

*Freie Universität Berlin, Berlin,* 

*Charles University of Prague, Praha,* 

Achim Schulte1, Bohumir Jansky2 and Julius Česak2 *1Institute of Geographical Sciences, Department of Earth Sciences,* 

Special Publication No. 210, American Society of Civil Engineers (ASCE), *Proceedings of the 5th International Conference on Scour and Erosion (ICSE-5)*, ISBN 978- 0-7844-1147-6, San Francisco, CA, USA, November 7-10, 2010, pp. 273-282

