This study try to reveal the effects of soil hydromechanical properties on gully erosion in the mollisol region of Northeast China. The authors conducted a long time monitoring of soil hydromechanical properties in both rainy and snow melting season, which were the key periods for gully expansion in the region. Though the gully headcut erosion has been well discussed, but few studies have analyzed gully head erosion based on continuous observation of soil hydrological parameters, which can help us to deep understand the mechanism of collapse of gully wall. Therefore, I suggest the manuscript could be accepted for publication after a minor revision. Following suggestions are my considerations for the authors.

1: The title and objective of this study did not show the key important finding of this study, I suggest the author to make the clear progress in these key parts including the hydromechanical properties.

1. Figure 11 (last figure) is the key finding and main contribution in the study domain of gully erosion, as it clearly clarifies the role of suction stress of storied water on soil loss from slope and gully bed respectively. In predicting the soil loss, the soil water storage (unit: mm) couldn’t equal to the event rainfall amount, but partially from the initial soil water. Therefore, I suggest the authors strength the application of the results of figure 11, or give some clear explanations.

3: Some figures are not clearly show the results: Fig 2, gully No II, the widths decreased from 2 to 3, which was confusion to me. Figure 3, normally the gully bed erosion rates was mainly caused by the runoff scouring, and many previous studies proved that the hydraulics of runoff in the rainy season significant higher than the snow melting runoff. So how do you explain the extremely high erosion rates of gully bed 1 in snowmelt season? Fig 8.a, the bar of “rainy events” is not clear, and in my opinion, showing the average rainfall of each rainfall grade can better reflect the impact on VWC.

Some important references need be cites, e.g. Hu Gang et al., (2007, 2009), Wu Yongqiu et al., (2008).

本研究揭示了我国东北部软土地区沟渠床土壤流失和陡峭边坡水力学性质的重要性。与以前在监测地点进行的沟渠侵蚀研究相比,这项工作清楚地表明了以前的研究未涉及的沟渠开发中一些未知但极其重要的方面,包括源头水文学、吸力应力及其对土壤流失的影响。在很多关于沟渠开发的研究中,大多数的研究工作都是只分析沟渠的回潮率、沟渠面积扩张、沟渠面积等。或根据降雨指数建立土壤流失方程,它们无法将陡峭侧墙观测到的土壤流失与水文因素结合起来,更不用说源头的水文机械状态了。因此,我建议经过一些微小的修改后,可以接受这项工作。下面的评论可以为作者考虑,并可能有助于提高手稿的质量。

1. 标题或摘要应该强调这项工作的重要发现。"3.4土壤水储存和排水"和图11中的方法充分说明,土壤损失预测不能来自于事件降雨,而应来自于先前的降水。在预测土壤流失时,考虑前期降水是合理的、合理的,因为土壤水分状况会极大地影响陡峭山坡的径流时间、强度和土壤稳定性。因此,我建议作者应该在讨论部分扩展这个结论。
2. 图6有些问题。为什么同一土壤的润湿干燥过程不同?是因为气压还是因为不同的测试程序?你能在文本中给出一些解释吗?这对读者有帮助吗?
3. 在引文中可以考虑有关径流和土壤流失的前期降水的参考资料。实际上,大多数的土壤流失预测(如USL方程)主要是基于降雨和径流因子。前期降水对径流因子的影响很大。

This work exhibits the important of hydro-mechanical properties on the soil loss in channel bed and on steep slope in the mollisol region of Northeast China. In comparison with previous studies on gully erosion at monitoring sites, the work clearly shows the some unknow, but extreme important aspects in the gully development that previous studies haven’t been addressed, including the headwater hydrology, suction stress, and their influence on the soil loss. In lots of studies on gully development, most works either solely analyze the channel head retreat rate, gully area expansion, gully area-volume, etc., or develop soil loss equation on rainfall index, they cannot combine the observed soil loss on steep sidewall, with the hydrological factors, not to mention the hydro-mechanical status in the headwaters. Therefore, I recommend the work could be accepted after some minor revisions. Following comments can be considered for the author and may be helpful for the quality improvements for the manuscript.

1. The title or the abstract should highlight the important finding of this work. The methods in “3.4 Soil water storage and drainage” and the figure 11 sufficiently illustrate that the soil loss prediction cannot be from the event rainfall, but from the antecedent precipitation. It is rational and logistical to consider antecedent precipitation in predicting soil loss because the soil water status greatly influent the time, intensity of runoff and the stability of soil on the steep slope. Therefore, I suggest the authors should extend the finding in the discussion part. 

2. I have some issues on the figure 6. Why the lines of wetting and drying process for the same soil are different? Is it because of the air pressure or different tests procedures? Can you give some explanations in the text? This would be helpful for the readers? 

3. Some references about the antecedent precipitation on the runoff or soil loss can be considered in citation. In fact, most of the soil loss prediction (such as USL equation) mainly base on the rainfall and runoff factor. The effect of antecedent precipitation has a great influence on the runoff factor.

It has been revised according to the opinions and agreed to hire. congratulations