# A Novel Suspended-Sediment Sampling Method: Depth-Integrated Grab (DIG)
## 5 Conclusions  
Even with the advancement of technology, sampling suspended sediment still remains the primary means of understanding fluvial suspended sediment. The novel DIG-SSC sampling method provided more accurate results than Grab-TSS, and results showed there was no significant difference between the DIG and EWDI methods. The DIG method is easier and cheaper to sample than with isokinetic samplers and EWDI sampling methods. However, DIG-SSC was only tested at 9 sites (48 sample pairs) within a range of river and suspended-sediment characteristics, so this method would benefit from further testing at other rivers with different river and suspended-sediment characteristics not represented in this study. Additional data collection could entail comparing the same number of verticals from EWDI and DIG. Collecting additional data to determine the IE, tow tank testing, and 3D modeling may help answer if the DIG sampler is isokinetic or not. Comparing the same number of verticals and isokinetic testing may help determine the cause of variability  
Figure 8: Suggested depth-integrated grab (DIG) suspended-sediment sampling setup for high (**a,b**) and low (**d**) stream velocities: (**a**) Depth-integrated grab (DIG) suspended-sediment sampler (US WBH-96 with a hole in the bottle’s cap) attached to a sounding weight; (**b**) A bridge board, A-55 sounding reel, US WBH-96 with a hole in the bottle’s cap attached to a sounding weight, and a person sampling from a bridge; (**c**) A bridge board, b–reel, and a person sampling from a bridge; (**d**) Depth-integrated grab (DIG) suspended-sediment sampler (US WBH-96 with a hole in the bottle’s cap) attached to a rope. between EWDI and DIG methods observed in this study. Answering these questions could help potential users know if this method could be applied at rivers beyond this study area. In addition to there being benefits of additional data collection, since this is a new sampling method, here are some important considerations when using the DIG method:  
1. The DIG method does not replace isokinetic samplers and EWDI methods but shows promise as an alternative if users are unable to use isokinetic samplers and EWDI sampling methods. 2. The DIG method may only be used at sites that are well mixed horizontally. If a site is poorly mixed horizontally, EWDI methods with a DIG sampler can be used. 3. Grab sampling often occurs at lower velocities as isokinetic samplers are not recommended. The DIG-SSC method could replace grab sampling at lower velocities. If users are unable to use the DIG-SSC method, here is one important consideration when using the Grab-TSS method:  
1. Grab-TSS may only be used as an estimate of suspended fines. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13137844/s1](https://www.mdpi.com/article/10.3390/app13137844/s1)]([https://www.mdpi.com/article/10.3390/app13137844/s1](https://www.mdpi.com/article/10.3390/app13137844/s1)), Table S1: All sampling-method comparison and river condition data for 9 river sites in Minnesota, 2018-2019. Conceptualization, J.T.G. ; methodology, J.T.G., J.W.L. and G.D.J. ; formal analysis, J.T.G. and S.B.L. ; investigation, J.T.G. and J.W.L. ; resources, J.T.G., G.D.J. and J.W.L. ; data curation, E.N.C. ; writing--original draft preparation, J.T.G., S.B.L. and E.N.C. ; writing--review and editing, J.T.G., S.B.L., J.W.L. and G.D.J. ; visualization, S.B.L., J.W.L. and E.N.C. ; supervision, J.T.G. ; project administration, J.T.G. and G.D.J. ; funding acquisition, J.T.G. and G.D.J. All authors have read and agreed to the published version of the manuscript. This research was funded by the Minnesota Clean Water Fund via the Minnesota Pollution Control Agency and U.S. Geological Survey Cooperator Matching Funds. Not applicable. The results from SSC and percentage fines laboratory analysis are available in the USGS National Water Information System [28]. The results from the TSS laboratory analyses are available from the Water Quality Portal [29].