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