Recent gully erosion intensity in an agricultural landscape underlain by fluvioglacial sediments (NE Czechia)

Abstract

AbstractInappropriate agricultural management practices combined with intense rainfall often lead to gully erosion. Knowledge of the causes and consequences of past erosion pulses is essential not only for farmers to improve land management, but also for municipalities to define infrastructure threats associated with material transport. This study comprehensively evaluates accelerated gully erosion and estimates gully transport capacity in fluvioglacial sediments left by a Pleistocene ice sheet in northeastern Czechia. Geomorphic mapping of an area of approximately 2 km2 revealed gullies up to 3.5 m wide and deep, with their heads starting at the boundaries of fields and pastures. The ground‐penetrating radar survey confirmed the presence of soil pipes contributing to gully formation due to unmaintained field drainage combined with the natural occurrence of soil pipes. Microscopic analysis and dendrogeomorphic dating of 102 cross‐sections from 28 exposed tree roots revealed 18 years of gully incision since 1985, with increased activity from 2007 to 2014. The mean incision rates ranged between 1–20 cm/year, but could reach 1 m during individual events. More intensive incisions were typical for soils with higher smectite content. The last severe erosion event in 2014 caused clogging of culverts and damage to infrastructure by transporting boulders up to 34 cm in diameter at critical flow velocities of 2.4–2.8 ms−1. Considering the predominance of human‐induced factors (e.g., current soil compaction due to grazing and failure to maintain the drainage pipe outlets), ongoing gully erosion can be expected during intense rainfall events unless appropriate agricultural or stabilization measures are addressed.