Organic material in the stream channel was surveyed in four locations on 8 Jan 2021 in dry channels that had not flowed since woody leaf senescence (Fig. 1a). The four sites were 1) upstream of the weir in the removal area watershed N2B (39.08995 N, 96.58900 W), 2) downstream of  removal area in watershed N2B in a channel with intact riparian forest (39.08994 N, 96.58859 W), 3) further downstream of the previous point, in mature gallery forest and at one of the long-term litter deposition sites (39.09867 N, 96.88967 W), and 4) in the control watershed N1B, in an area of younger riparian forest with small trees (39.08656 N, 96.57703 W).  Each site had 10- 0.25 m2 quadrats spaced over a few hundred meters. We took 10-20 paces upstream and blindly cast the quadrat into the channel. All leaves, small wood, and seed parts were collected from inside the quadrat and weighed in the field. For large samples, the entire damp sample was weighed and a ~30 g subsample was placed in a paper bag to assess damp mass to dry mass. The entire sample was taken and weighed for smaller samples. The subsamples were weighed again and then the bag alone after 3 days drying at 60 °C. The proportion of damp to wet mass for each sample was used to correct dry mass of the entire sample. A subset of 18 samples of collected leaves was ashed at 450 °C to determine ash free dry mass (AFDM) to dry mass ratios. This factor was 0.74 with a standard deviation of 0.07.