Mangrove Propagule Tidal Dispersal — 2D

Tidal Forcing

Tidal current amplitude U₀ 0.28 m/s

Tidal period T 50 s

Propagule Physics

Drag response time τ 2.0 s

Root capture density 0.55

Live Readouts

Stranded

Mean drift (afloat)

0.0 m

Tide elevation η(t)

0.00 m — slack

How it works

This is a Hovmöller (distance–time) strip chart, a standard oceanographic technique for tracking dispersal along one spatial axis through time — not a top-down map. The horizontal axis is cross-channel position z (bank ↔ bank); the vertical axis is time, scrolling as the simulation runs, newest at the bottom. Background shading is the local water depth field h(z,t) at that instant; each propagule leaves a bright trail tracing its own z(t) as the strip scrolls past it.

Tide elevation:  η(t) = A·sin(2πt/T)
Tidal current:   u(t) = U₀·cos(2πt/T)   (along-channel, drives drift stat only)
Cross-channel:   dvz/dt = −vz/τ + noise(√dt)     (Langevin/Ornstein–Uhlenbeck)
Local depth:     h(z,t) = h₀ − k·|z| + η(t)
Stranding:       if h(z,t) < h_strand and |z| in root fringe →
                  captured with probability ∝ root density · dt (Poisson process)

U₀, T — the along-channel flood/ebb current. It does not steer a propagule across the strip (that's governed only by the lateral relaxation/noise term) but sets how far it drifts along the channel — read out as "Mean drift".
τ — how tightly a propagule's cross-channel velocity relaxes toward zero. Small τ damps lateral wandering quickly (tight trails); large τ lets random turbulent kicks build up more lateral spread (a released-from-rest particle's spread grows as t³ at first, crossing over to ordinary t¹ diffusion once t ≫ τ).
Root capture density — the probability per unit time that a propagule sitting over exposed, shallow fringe at low tide is mechanically trapped. Capture times follow an exponential (Poisson) distribution with mean 1/(root density × 0.9).
The scrolling background reveals the tide cycle directly: dark blue bands are submerged fringe, brown bands are exposed mud at low tide — trails that reach a brown band and stop are strandings.

Mirrors field/hydrodynamic studies of mangrove propagule dispersal (e.g. Van der Stocken et al.), where residence time near suitable banks at the right tidal phase — not just current speed — governs establishment versus long-distance export.

← bank fringe · mid-channel · bank fringe →
↓ time (newest at bottom)

Flood tide

Afloat propagule trail Stranded (trail stops) Submerged fringe / mud

Mangrove Propagule Tidal Dispersal — 2D Strip Chart