| Table 1. Comparison of LiDAR data point densities, DEM cell sizes, and interpolation methods in overland flow routing, which are the main results of this study aiming at improved stream extraction and soil wetness mapping within a forested catchment. In general, breaching leads to more realistic flow paths than filling, and the changes in DEM are smaller on average with breaching. The more overlapping stream/ditch segments were found in the stream extraction, the better flow routing corresponds to the topographical database maintained by the NLS (2021b). However, raster cell may affect flow accumulation, thus the overlaps should not be compared with different cell sizes. Key flow paths were selected so that they were located along the main waterways and were divided roughly evenly within the catchment. | ||||||||||||
| Low-density airborne LiDAR | High-density airborne LiDAR | |||||||||||
| DEM cell size | 1 m | 2 m | 1 m | 2 m | ||||||||
| Interpolation method | TIN | IDW | Kriging | TIN | IDW | Kriging | TIN | IDW | Kriging | TIN | IDW | Kriging |
| Share of remodeled raster cells in conditioned DEM: | ||||||||||||
| Breached cells (>10 cm) | 1.4% | 1.1% | 1.1% | 4.6% | 3.1% | 4.5% | 3.9 % | 3.1% | 3.9% | 6.3% | 5.8% | 6.6% |
| Mean breach depth [m] | –0.18 | –0.11 | –0.12 | –0.14 | –0.13 | –0.14 | –0.12 | –0.11 | –0.12 | –0.16 | –0.16 | –0.17 |
| Filled cells (>10 cm) | 6.0% | 5.9% | 4.9% | 5.8% | 5.6% | 5.1% | 3.4% | 5.6% | 2.8% | 6.4% | 5.6% | 4.0% |
| Mean filling height [m] | 0.62 | 0.51 | 0.43 | 0.45 | 0.48 | 0.37 | 0.53 | 0.46 | 0.44 | 0.52 | 0.55 | 0.35 |
| Overlapped streams/ditches using different channelization thresholds: | ||||||||||||
| 0.1 ha | 73% | 73% | 74% | 70% | 70% | 71% | 76% | 76% | 76% | 72% | 72% | 72% |
| 0.2 ha | 63% | 63% | 64% | 61% | 61% | 62% | 67% | 67% | 67% | 63% | 64% | 64% |
| 0.5 ha | 49% | 50% | 50% | 48% | 48% | 49% | 52% | 53% | 53% | 50% | 50% | 50% |
| 1.0 ha | 38% | 39% | 38% | 37% | 37% | 38% | 39% | 40% | 40% | 38% | 38% | 38% |
| Key flow paths found: | ||||||||||||
| Culverts (n = 20) | 75% | 70% | 75% | 60% | 55% | 60% | 75% | 85% | 85% | 65% | 80% | 85% |
| Streams/ditches (n = 20) | 65% | 55% | 80% | 55% | 70% | 55% | 70% | 85% | 85% | 80% | 90% | 85% |
| Altogether (n = 40) | 70% | 63% | 78% | 58% | 63% | 58% | 73% | 85% | 85% | 73% | 85% | 85% |