First: treat the ground as suspect
The visible depression is usually a fraction of the cavity beneath it. Compacted, root-bound surface soil bridges a void well, which is precisely why the surface still looks like ground.
So before anything else, keep vehicles, equipment and foot traffic off the area. This applies particularly to anything heavy — a vehicle crossing ground that supports a person is a different load case entirely.
If the area is near a pool deck, slab, walkway or footing, note that those structures may have lost bearing support even if nothing has visibly moved.
Second: document it before anything changes
Five minutes of photography now is worth a great deal later.
- A wide shot showing the whole wall and where the affected area sits along it
- Close-ups of the depression, with something in frame for scale
- The ground immediately behind the wall along its full length
- The wall face at the lowest tide you can catch — it exposes far more of the structure
- Anything exposed that looks like hardware: rod ends, plates, the back of the cap
- A note of the date and what you have noticed changing
Third: watch the wall on a falling tide
This is the most informative thing you can do yourself, and it takes one observation at the right moment.
As the tide drops, water behind the wall drains. Watch where it comes out and what it looks like.
Clear water from weep holes is drainage working as designed. Cloudy or tinted water, or water coming through panel joints and cracks rather than from weep holes, is backfill in transit — and it tells you roughly where the pathway is.
Look also at the bottom beneath any discharge point for a fan of fine sediment building up. That is your soil.
- 1Clear water from a weep hole — drainage working exactly as designed
- 2A crack through the panel becomes an unfiltered route out
- 3Cloudy discharge and a sediment fan below it — backfill leaving the property
Fourth: deal with what you control
Two things are genuinely within a property owner’s reach and both reduce the load on the wall.
Redirect stormwater. Downspouts, deck drains and regraded areas that discharge near the top of a wall erode backfill from the land side, entirely independently of anything happening at the waterline. Moving that discharge away from the wall is frequently the cheapest meaningful improvement available on a waterfront lot.
Clear the weep holes. Blocked drainage does not just raise pressure behind the wall — it actively drives water toward whatever unfiltered opening is available, which means it drives soil out. Clearing them is maintenance, not repair, and it matters.
What not to do
Three common responses that tend to make things worse or hide the problem.
Do not just fill the depression
Fill added to an active pathway follows the original soil out, and in the meantime the void underneath keeps growing where nobody can see it.
Do not seal the leak from the water side
Blocking a visible discharge without providing filtered drainage can raise pressure behind the wall and relocate the discharge to the next weakest point.
Do not climb on or near a wall that has moved
And do not go into the water to get a better look at the toe. Photographs from stable ground are enough to start with.
Frequently asked questions
How urgent is this?
Soil loss does not stabilise on its own — the mechanism that caused it continues until something changes. It is rarely an emergency on the day you spot it, and it is reliably more expensive the longer it runs. Getting it looked at within weeks rather than seasons is a reasonable standard.
Can I fill it temporarily to stop someone falling in?
Marking and fencing the area off is safer and more honest than filling it, because fill conceals the extent without addressing anything and can give a false impression that the ground is sound.
What should I have ready for an assessment?
Your photographs, roughly when you first noticed it, whether it has changed, what the wall is made of if you know, and approximately how much of the wall is affected. That is enough to start.