Ground-penetrating radar profiling on embanked floodplains

Abstract

The extreme floods of 1993/94 and 1995 have demonstrated that river management is of crucial interest for the Dutch population, of which most live below flood stage level. Middelkoop (1997) has shown how embanked floodplains along the major rivers in the central Netherlands have experienced gradual decrease in accommodation space due to frequent deposition of mud drapes and sand during floods. Middelkoops results were based on the examination of historical maps and geochemical characterization of heavy metals in overbank deposits. In the light of a likely increase in extreme floods in the near future, river management is increasingly dependent on accurate assessment of recent sedimentation rates in the embanked floodplains and the resultant decrease of accommodation space. Assessment of sedimentation rates in embanked floodplains is also of interest for sand and clay exploitation in these areas.In order to develop new research techniques for measuring sedimentation rates on embanked floodplains, an example near Winssen, along the river Waal, was studied. This site was selected because it is (largely) undisturbed and has the availability of historical age control.Following Middelkoops' findings, sedimentation on floodplains is now studied using a combination of geophysical profiling, coring, geochemical analysis and OSL dating. This multidisciplinary approach allows a more comprehensive description and interpretation of overbank sedimentation. The purpose of this paper is to discuss the results of the geophysical profiling. Geological and historical setting of the Rhine-Meuse floodplain near WinssenThe embanked floodplain of Winssen is situated along the river Waal, the major branch of the Rhine (Fig. 1). Between 1050 and 1350 AD the Waal was embanked by man (Pons, 1957) and the original floodplains (Fig. 1) were isolated from the active river. Between the time of the embankment and about 1600 AD, the confined river channel eroded parts of the pre-embankment deposits within the channel between the embankments (Middelkoop, 1997). An additional effect of the embankment A number of radar facies units were recognized. Boreholes were used to relate radar facies units to sedimentary facies and to determine radar velocity. The GPR groundwave is affected by differences in moisture and texture of the top layer and probably interferes with the first subsurface reflector. The architectural elements recognized in the GPR transects confirm earlier reported insights on human-influenced river behaviour. This is testified in the development of sand bars during flood regimes that are probably more widespread than previously established.

Selection of integration time intervals for quartz OSL decay curves

“…Historical maps of the area indicate that the section of floodplain from which the sample was taken was formed between 1723 and 1810 AD (Middelkoop, 1997;Bakker et al, 2007  Sample NCL-1107136 is from a very young embanked floodplain of the River Waal (Hobo et. al, 2010).…”

Evaluation of hydraulic conductivity of subsoil using electrical resistivity and ground penetrating radar data: example from Southwestern Nigeria

“…The Radargrams produced along the eight traverses (traverses 1, 2, 3, 4, 5, 6, 7 and 8) are presented and analyzed (Figs. 5,6,7,8) showing three subsurface layers namely; the lateritic topsoil, weathered layer (subsoil) and lastly the basement.…”

Exploring Integrated Geophysics and Geotechnics as a Paleolandscape Reconstruction Tool: Archaeological Prospection of (Prehistoric) Sites Buried Deeply below the Scheldt Polders (NW Belgium)

“…The results of GPR would provide the best models of the subsurface (e.g. Bakker et al, ; Vandenberghe and van Overmeeren, ) but the method is hindered by the presence of clay and brackish groundwater (Olhoeft, ) and was therefore not suitable in our case. De Smedt et al () and Conyers et al () have mapped shallow (pre‐)historic paleolandscapes in alluvial plains in an archaeological context using frequency domain EMI survey supported by a limited number of handcorings.…”