Controls on the development of continuous gullies: A 60 year monitoring study in the Moldavian Plateau of Romania

Abstract

Gully erosion is a major environmental threat on the Moldavian Plateau (MP) of eastern Romania. The permanent gully systems consist of two main gully types. These are: (1) discontinuous gullies, which are mostly located on hillslopes and (2) large continuous gullies in valley bottoms. Very few studies have investigated the evolution of continuous gullies over the medium to longer term. The main objective of this study was to quantitatively analyse the development of continuous gullies over six decades . The article aimed at predicting temporal patterns of gully head erosion based on field data from multiple gullies.Fourteen representative continuous gullies were selected near the town of Barlad, most of them having catchment areas < 500 ha. Linear gully head retreat (LGHR) and areal gully growth (AGG) rates were quantified for six decades. Two main periods were distinguished and compared (i.e., the wet 1961-1980 period and the drier 1981-2020 period). Results indicate that gully erosion rates have significantly decreased since 1981. The mean LGHR of 7.7 m yr À1 over 60 years was accompanied by a mean AGG of 213 m 2 yr À1 . However, erosion rates between 1961 and 1980 were 4.0 times larger for LGHR and 5.9 times more for AGG compared to those for 1981-2020.Two regression models indicate that annual precipitation depth (P) is the primary controlling factor, explaining 57% of LGHR and 53% of AGG rate. The contributing area (CA) follows, with $33%. Only 43% of total change in LGHR and 46% of total change in AGG results from rainfall-induced runoff during the warm season. Accordingly, the cold season (with associated freeze-thaw processes and snowmelt runoff) has more impact on gully development. The runoff pattern, when flow enters the trunk gully head, is largely controlled by the upper approaching discontinuous gully.areal gully growth, cold season, hydraulic radius, linear gully head retreat, runoff pattern | INTRODUCTIONGenerally, the rate of gully growth is most closely related to the topographic position of the gully head than to any other single factor (Brice, 1966). Logically, this means that gully growth is mainly controlled by the size of the catchment area (CA) upstream of the gully head. Some authors have advocated that the decrease in gully growth rate results from the associated decrease in gully CA and

Root Distribution and Soil Properties of Gully Heads and Their Effects on Headcut Migration in the Mollisols Region of Northeast China

“…This result was close to the result reported by Hu et al [39] and Wu et al [40] in rolling hill areas in black soil of northeast China [39,40], and it was also within the range of Vanmaercke et al [6] who reported that linear, areal, and volumetric migration rate were 0.01-135 m yr −1 , 0.01-3628 m 2 yr −1 and 0.002-47430 m 3 yr −1 , respectively, through compiling the 933 individual gullies from 70 study areas in 25 countries of six continents that reflected a wide range of environmental conditions and gully headcut retreat globally. However, our results were distinctly greater than the result in the other study areas worldwide [12,[54][55][56][57]. For example, Frankl et al [56] found that the linear, areal, and volumetric retreat rate were 0.34 m yr −1 , 1.70 m 2 yr −1 and 5.20 m 3 yr −1 over the rainy reason of 2010, respectively, while larger rates were found during medium to long time periods (1-47 years), with averages of 3.8 m yr −1 , 31.5 m 2 yr −1 and 47.7 m 3 yr −1 in northern Ethiopia, respectively.…”

Natural multi-hazard risk perception and educational insights among Geography and Tourism students and graduates amid the Covid-19 pandemic

“…The most recent and impactful floods in Northern Serbia took place along the Danube and Tisa floodplains in 2013 [ 105 ], and their tributaries in 2014 [ 106 ]. Soil erosion and landslides are widespread in both regions due to a large spectrum of natural settings such as geological structure and lithology [ [107] , [108] , [109] ], relief fragmentation, soil properties, climate and hydrographic network particularities, but also due to the influence of anthropogenic factors [ [110] , [111] , [112] ].…”

Soil Conservation Measures on Degraded Land in the Hilly Region of Eastern Romania: A Case Study from Puriceni-Bahnari Catchment

“…By using the data collected from the field, the gully erosion in the Puriceni-Bahnari catchment was drawn up. Thus, the presence of the two main gully types that are specific to the Barlad Plateau can be noticed, namely, continuous gullies on the valley bottom [50] and discontinuous gullies on the valley side [51] (Figure 8). At the catchment level, the mean value of annual soil loss on the agricultural land due to soil erosion amounted to 15.46 t•ha −1 •yr −1 (13,500 t•yr -1 ).…”