This script post-processes Delft3D-4 accumulated seabed flux output to generate seabed sediment distribution maps. The main workflow implements the Central accumulated sediment flux (ASF) approach: it compresses the flux time series per grain size, combines positive (depositional) and negative (erosional) fluxes, and converts the result into relative grain-size availability and bed-layer fractions.
- Reads accumulated flux MAT files for multiple grain-size classes and a hydrodynamic grid MAT file (HDF5 / v7.3 format).
- Separates positive and negative fluxes and applies a chosen statistical operator (e.g. mean, percentiles, trimmed mean / ASF).
- Combines positive and negative components according to a selected analysis method (ASF is the default).
- Optionally applies simple shear-stress-based weighting between grain-size classes.
- Normalises the combined flux per cell across grain sizes to obtain:
- percentage contribution of each size class, and
- bed-layer fractions suitable as input for morphodynamic models.
- Optionally computes a D50 map from the ASF-based grain-size percentages.
- Writes all outputs as
.xyztext files (X Y Z) that can be imported into GIS or plotting software.
Operation (op) options – time-series statistic per grain size and flux sign (positive = deposition and negative = erosion) for each grid cell
op |
Name | Description (per grid cell, per grain, per sign) | Extra input/notes |
|---|---|---|---|
| 1 | Mean | NaN-aware arithmetic mean of the flux time series | Works for all analyses 1–7 |
| 2 | 95th percentile | 95th percentile of flux values | |
| 3 | Minimum | Minimum flux value | |
| 4 | Maximum | Maximum flux value | |
| 5 | Median | Median flux value | |
| 6 | Trimmed mean (ASF core) | Mean over the interquartile range (25–75 %); returns both trimmed mean and counts N_trim |
Needed for ASF when combined with analysis = 6 |
| 7 | 75th percentile | 75th percentile of flux values | |
| 8 | Exceedance mean | Mean of values above the exceed_pct percentile |
Uses exceed_pct (default 25 %) |
| 9 | BSS-conditioned mean | Mean of flux values at times when BSS exceeds its exceed_pct percentile |
Requires BSS file with matching time dimension |
For
analysis = 7(CFR), the sameopcodes are applied to positive/negative flux magnitudes before forming the cumulative flux ratio.
analysis |
Name | Description (per grid cell, per grain) | Special requirements / comments |
|---|---|---|---|
| 1 | Threshold split | Uses positive statistic for grain sizes ≤ thresh and negative statistic for grain sizes > thresh |
Requires thresh and grain sizes on both sides of the threshold |
| 2 | Positive only | Uses only the positive (depositional) statistic | |
| 3 | Negative only | Uses only the negative (erosional, absolute value) statistic | |
| 4 | Residual depositional flux | Positive − negative; negative values clipped to 0 (emphasises net deposition) | Requires both pos and neg stats (analyses 1–6) |
| 5 | Geometric-mean transport | √(pos · neg), with small epsilon; emphasises co-occurrence of deposition and erosion | Requires both pos and neg stats |
| 6 | Total transport / ASF | If op = 6 and N_trim available: ASF = μ⁺·N⁺ + μ⁻·N⁻; otherwise total = pos + neg |
ASF configuration is op = 6, analysis = 6 |
| 7 | Cumulative flux ratio (CFR) | Ratio of positive to negative statistics minus 1, i.e. CFR − 1, computed from sign-separated flux fields | Uses only CFR branch in operate_mat (choice = 3) |
| Purpose | Recommended setting | Comment |
|---|---|---|
| ASF sediment distribution (default) | op = 6, analysis = 6 |
Central, frequency-weighted gross exchange per grain |
| Simple depositional intensity | op = 1,2,5,7, analysis = 2 |
Deposition (Positive) flux only |
| Simple erosional intensity | op = 1,2,5,7, analysis = 3 |
Erosion (Negative) flux only (absolute values) |
| Net residual deposition | op = 1 or 6, analysis = 4 |
Highlights areas of persistent deposition |
| CFR diagnostics | op = 1–9, analysis = 7 |
Different op give different CFR summaries |