Micro-topographical surface alteration caused by tillage and irrigation canal maintenance and its consequences on excess water development

The most common forms of low relief plains created by agriculture are ridges and furrows that develop parallel to ploughing and irrigation or drainage canals. These micro-forms influence the surface run-off conditions of a field, as they act as overland flow paths or barriers depending on their orientation, resulting in the development of excess water. The consequences of excess water retention are soil degradation and crop loss, which for example, in 2011 threatened 11% of the agricultural lands of Hungary. The goals of the present research are to evaluate the spatial distribution and morphology of forms created by tillage and irrigation or drainage canal maintenance, and to study their effect from the point-of-view of blocked drainage and excess water build-up. The studied tillage ridges were formed during the last 20 years and their height reaches 0.19-0.26 m. The ridges block the overland flow and facilitate the development of excess water on 14.1% of the study area. Along 85.4% of the canal banks canal berms appear. Their average height is 0.38 m (max: 1.43 m) and width is 17 m (max: 54.8 m). Considering the height of the tillage ridges, they have less influence on overland flow than that of the canal berms, but, due to the low relief of the area, both play an important role in disconnecting overland flow routes. Thus (dis)connectivity could develop within an agricultural plot as the higher parts of the plot could be disconnected from the lower parts by ridges, and the canal berms disconnect the plot and the artificial drainage system. Regarding overland flow, ridges and berms disconnect the plots from their drainage canals (buffer function), and in the natural drainage routes they act as barriers. The dis-connectivity function of the studied forms increases over time and as a result of intensive tillage. Therefore, they will play a more and more important role in altering overland flow and developing excess water hazard.