bank erosion assessment - europa · the mathematical model bstem (bank stability and toe erosion...
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Bank erosion assessment
Erosion Modelling WorkshopJoint Research Centre
Ispra, Italy20-22 March 2017
Maria Lilli, Environmental Engineer, MScTechnical University of Crete (TUC)
Greece
River bank erosion assessment
Bank failures occur by gravity requiring evaluation of geotechnical variables
70-90% of sediment comes from bank Problems of bridge failure and loss of
agricultural land Downstream problems from
sedimentation, flooding and habitat loss
Steep land slopes… Flush floods…
Relate flood events to bank restoration measuresBank restoration measuresE.A. Varouchakis, G.V. Giannakis, M.A. Lilli, E. Ioannidou, N.P. Nikolaidis, and G.P. Karatzas, 2016, “Development of a statistical tool for the
estimation of riverbank erosion probability”, SOIL, 2: 1-11
The BSTEM model results together with field inspection were used to setup the statistical model by interpreting the erosion existence in terms of binary data (1 = “presence of erosion” and 0 = “no erosion”).
The probability of erosion at the riverbanks of River Koiliaris, was estimated considering a series of easy to determine independent geomorphological variables (bank slope, river cross section) through LR and LWLR methodologiesStatistical model
use restored sites at Koiliaris CZO and Evrotas River Basin in GreeceVerification
Estimation of the ratio of flood volume to precipitation volume (Vf/VR) andits relationship with Bank Erosion Indicator (BEI) and the stability factor (Fs)provided by BSTEM.
Creation of an empirical mathematical equation that correlatesprecipitation volume, stability factor and median grain size of soil of thebank.
In this way the bank stability factor can be related to BEI through Vf/VR and to expedited type of surveys.
Define bank failure thresholds Fs= 0-1 unstable
Fs= 1-1.5 partial failureFs>1.5 stable
The mathematical model BSTEM (Bank Stability and Toe Erosion Model) was developed by A. Simon, A.Curini, R. Thomas and N. Bankhead, who are members of National Sedimentation Laboratory of USDepartment of Agriculture.
BSTEM Model – Simulation of bank failure
Baseflow separation and flood depths.The segment was divided into sections and 9 locations were chosen forfurther analysis.
Hydrograph analysis
field surveyslocation of bank failure sites3-D representation of the river segmenthydrological datasediment analysis for texture
Data collection
Bank erosion assessment methodology
Thank you