GCS nesting analysis outputs

Methodology + motivation

  • Cross-sections along each of the selected flow stage centerlines are aligned to the longest centerline path (typically the lowest flow stage) based on Euclidian distance.

  • Ws, Zs, C(Ws, Zs) values are aligned for all flow stages, faciliating comparison.

  • GCS nesting analysis attempts to capture the nested hierarchical topographic structure of the study river.

  • Nesting patterns associated with landforms can be provide insight into which flow stages (and their respective discharges) contribute to maintaining desirable aspects of channel topography such as riffle-pool sequences, or heterogeneity broadly.

Outputs

Directory Location: By default all nesting analysis outputs are saved @ GCS_analysis_outputs/nesting_analysis/.

Visual Outputs:

Static .png plots visualizing Ws, Zs, and C(Ws, Zs) series where each flow stage is stacked in a single plot, i.e., Ws_nesting_gcs_plots.png (see example below).

../_images/Ws_nesting_gcs_plots.png

Interactive HTML “Sankey Diagrams” visualizing cross-section landform transitions between each increasing flow stage. The code outputs one with ‘normal’ cross-sections included, and another focusing only on non-normal GCS landforms (see the static example below).

../_images/hover_gcs_sankey.png

Tabular Ouputs:

  • A .csv table with Chi-squared significance levels associated for all landform transitions between flow stages. landform_transitions_chi_square.csv.

    • Note that the Chi-squared expected frequency parameter is defined by the relative landform abundance at the higher flow stage for a given transition.

    • For example, take a river where 50% of cross-sections that are nozzles (narrow and shallow) at a 0.7ft flow stage transition into wide bars (wide and shallow) at a 1.2ft flow stage. If wide bar cross-sections only represent 20% of the higher flow stage, we can say that nozzles preferentially transition into wide bars if significant at the p < 0.05 level.

  • A .csv table with results from a T-Test comparing the the relative width (Ws) values of cross-sections with Zs < -0.5 and Zs > 0.5 at the next higher flow stage.

    • The idea here is to see whether high and low elevation cross-sections have some preferential relationship with channel geometry at the next-higher flow stage.

    • Output: preferential_nesting_ttest.csv.