Simulation and comparison of stream power in-channel and on the floodplain in a German lowland area

Abstract

Extensive lowland floodplains cover substantial parts of the glacially formed landscape of Northern Germany. Stream power is recognized as a force of formation and development of the river morphology and an interaction system between channel and floodplain. In order to understand the effects of the river power and flood power, HEC-RAS models were set up for ten river sections in the Upper Stör catchment, based on a 1 m digital elevation model and field data, sampled during a moderate water level period (September, 2011), flood season (January, 2012) and dry season (April, 2012). The models were proven to be highly efficient and accurate through the seasonal roughness modification. The coefficients of determination (R 2 ) of the calibrated models were 0.90, 0.90, 0.93 and 0.95 respectively. Combined with the continuous and long-term data support from SWAT model, the stream power both in-channel and on the floodplain was analysed. Results show that the 10-year-averaged discharge and unit stream power were around 1/3 of bankfull discharge and unit power, and the 10-year-peak discharge and unit stream power were nearly 1.6 times the bankfull conditions. Unit stream power was proportional to the increase of stream discharge, while the increase rate of unit in-channel stream power was 3 times higher than that of unit stream power on the floodplain. Finally, the distribution of the hydraulic parameters under 10-years-peak discharge conditions was shown, indicating that only 1-10% of flow stream was generated by floodplain flow, but 40-75% volume of water was located on the floodplain. The variation of the increasing rate of the stream power was dominated by the local roughness height, while the stream power distributed on the floodplain mainly depended on the local slope of the sub-catchment.

Impact of conservation practices on runoff and soil loss in the sub-humid Ethiopian Highlands: The Debre Mawi watershed

“…Later in the rainy season (Fig. 8), the sediment concentrations decrease because the rill formation and expansion decline (Tebebu et al, 2010;Tilahun et al, 2013a;Tilahun et al, 2013b;Zegeye et al, 2010) with greater concentrations during high flow events compared to the small storms due to less stream power (Song et al, 2014). Though concentrations decrease due to the vegetation cover, unlike in developed countries, the cover does not provide full canopy because of the low nutrient status of the soils and lower fertilizer application in the Debre Mawi watershed.…”

Being an expert witness in geomorphology

“…4). Calculations of unit stream power using HEC-RAS (see for example, Song et al, 2014) by Professor Hugo Loaiciga, member of our research team (Loaiciga, personal written communication, 2008), and the author concluded that Unit stream power in 2005 against the bluff at Monte Vista across from the levee at Live Oak Acres was about 800 W/m 2 --sufficient using Costa (1983) to move boulders up to about 1000 mm in diameter. By comparison, the unit stream power just upstream of the levee against the eastern bank of the river was about 115 W/m 2 ) --sufficient to move particles of about 200 mm diameter (Costa, 1983).…”

Watershed Spatial Discretization for the Analysis of Land Use Change in Coastal Regions

“…For the drainage network ordering process, we estimated a length of 100 m based on field survey observations. The final catchment extraction and merge operations were performed using pre-defined outflow points, based on the water course distribution, easily accessible and suitable to measure with flow meters (Song et al, 2014).…”

“…Song et al (2014) described this as the first step before analyzing the alluvial and hydrological effects of river and estuarine systems. In the absence of a sub-basin discharge monitoring, it becomes more efficient and realistic to estimate the basin hydrological parameters if the spatial distribution is consistent.…”

“…Geographical and climatic features result in regions prone to flooding, such as high water tables, coastlines with orographic precipitation, and extensive lowlands with large perennial rivers (Dutta, 2011;Song et al, 2014). Floods occur when river flow overtops natural and artificial banks, spreading water over the surrounding plains (Aggarwal et al, 2014).…”