Yes, parts of Marchwood are at real risk of flooding, and it is the one thing about the village you cannot afford to be relaxed about. This is low ground near the mouth of a river, close enough to the water that the water is a factor and not just a view. Some streets sit in the higher flood zones, a fair share carry a surface-water risk, and the long-range picture gets worse rather than better. None of it makes the place uninhabitable. All of it makes the address you choose matter more than usual.
On river and sea flooding, the split is stark from street to street. Only a small slice of Marchwood, under one in fifty of its area, sits in the middle flood zone, but about one in seven falls in the highest zone, the band the Environment Agency keeps for land with a genuine chance of flooding in any given year. That is not a background hum. That is a real fraction of the village where the risk is on the table every winter, and it clusters on the low, waterside ground rather than spreading itself evenly.
Surface water is the quieter menace, and it is more widespread. Nearly one in five postcodes here carry a high surface-water flood risk, another one in five sit in the medium band, and getting on for half have at least some low-level risk. Surface water is the flooding that arrives not from the river but from a downpour the drains cannot swallow fast enough, and flat, low ground of this kind is exactly where it gathers. It is less cinematic than a bursting river and just as good at ruining a ground floor.
Looking forward, the trend points the wrong way. Once the climate allowance is folded in, the share of Marchwood in the higher-risk flood zone climbs to about a third, which is the planners' polite way of saying that homes safe today are not all guaranteed to stay that way. Buying here is a decision about the next few decades, not just the next survey.
For insurance, that matters in actual money. A property in a high flood zone can mean a steeper premium, a bigger excess, and some paperwork before a policy is written, and lenders pay attention to the same thing. It is usually still insurable, but insurable and cheap are not the same word. Get a quote on the specific house before you commit, not after you have.
So the honest verdict is that flooding is Marchwood's real weak spot, the one dimension where the village scores poorly and earns the mark. The Forest and the quiet are the reward. The water is the price, and it is paid one contour line at a time.