Step 2: Hydrology Assessment

Learning how water enters, moves through, and drains from the site to uncover hydrological barriers

Restoration succeeds or fails on hydrology. Even perfect planting, high-quality propagules, and careful nursery work cannot overcome a site where water no longer moves as it should. Step 2 guides you through understanding the tidal pathways, freshwater inputs, and subtle topographic features that determine whether a mangrove system can sustain itself again.

If Step 1 taught you how to read the landscape, Step 2 teaches you how to read its circulation.

Following the Path of Water

Begin by tracing the main routes that water takes to reach and leave the site. Move slowly and deliberately, following each channel, culvert, or inlet. Notice how wide or narrow they are, whether sediment has built up at their mouths, and whether they still connect directly to the sea.

Some channels may look open but sit just high enough that they only function during the highest tides. Others may have been altered by storm deposits, excavated unintentionally, or partially blocked by vegetation debris.

Your goal is to understand not just where water is, but where it wants to go — and what stands in its way.

Understanding Tidal Reach and Hydroperiod

Every mangrove species depends on a specific flooding regime. Some zones tolerate daily inundation; others require occasional tidal wetting. Step 2 asks you to map this pattern in your mind.

Walk the site during different tide stages when possible. At low tide, note which areas drain fully and which remain flooded. At high tide, observe which areas fill first, which fill last, and which remain dry altogether.

Hydrology often reveals itself through small clues:

debris lines from the last high tides,
barnacles or encrusting organisms marking past water levels,
changes in sediment firmness,
zones where pneumatophores cluster densely.

Try to imagine the hydroperiod not as a single moment, but as a rhythm — a pattern that repeats day after day and determines whether sediments receive enough oxygenation to avoid stagnation.

Identifying Barriers and Artificial Blockages

Many hydrological problems are human-made, even if unintentional. A small berm built to stabilize a road. A culvert buried over time. A storm drain redirected during construction. These structures can isolate whole sections of a wetland.

Look for:

culverts that are too small, clogged, or positioned above tidal height;
road edges acting as unintended dikes;
backfilled or abandoned channels;
storm wrack blocking natural flow paths;
sediment deltas formed where runoff meets still water.

Sometimes the barrier is subtle — just a few centimeters of compacted fill — yet enough to cut off tidal exchange. Mapping these restrictions, even informally, is essential before any intervention.

Following Freshwater Inputs Across Seasons

Hydrology is not only tidal. Freshwater arrives from hillsides, streams, storm drains, and occasional springs. In Grenada, wet-season rainfall can dramatically reshape water levels and sediment movement.

During the wet season, freshwater pulses:

deliver sediment,
dilute salinity,
create short-term flooding,
carry debris or nutrients into mangrove basins.

During the dry season, diminished freshwater can raise salinity, concentrate stagnation, or alter the soil’s sulphide balance.

Step 2 asks you to consider both conditions. Sites often behave differently across seasons, and restoration planning must reflect this variability.

Mapping Microtopography and Flow Pathways

Hydrology is deeply tied to elevation — not large differences, but very small ones. A slight rise may keep an area dry for months; a shallow depression may trap water long after the tide retreats.

Walk the site slowly and observe the patterns:

Where does water linger after low tide?
Where does sediment accumulate?
Where do seedlings cluster or fail?
Which areas feel firmer underfoot?

These micro-patterns often reveal the most important questions:

Is the site draining as it once did?
Is water being held longer than the ecosystem can tolerate?
Has storm deposition reshaped the drainage lines?

Understanding these subtleties guides decisions in Step 3, when hydrological repair is designed.

Recognizing Hydrological Stress Signals

Hydrological failure often expresses itself long before sediment or vegetation collapse.

Common early signals include:

algal mats in areas that should flush out,
isolated pools with deep organic sludge,
sharp transitions between healthy and failing vegetation,
salt crusts that appear only after a new drain is installed,
seedlings succeeding in one corner and universally failing in another.

None of these signs exist in isolation. Step 2 helps you connect them back to water movement.

Integrating Hydrological Observations

By the end of Step 2, you should have a clear understanding of:

how the tide reaches the site,
how long water stays in each zone,
what blocks or slows its movement,
how freshwater behaves across seasons,
and how microtopography shapes drainage.

This knowledge allows you to determine whether hydrological modification is necessary — whether the site needs a cleared channel, a reopened culvert, a lowered berm, or simply the removal of storm debris.

Only after hydrology is understood and corrected do planting decisions become meaningful.