How to Assess Windthrow Risk on Your Property

A mature tree can look perfectly sound from the ground, then move or fail when saturated soil and strong winds arrive together. To assess windthrow risk properly, you need to consider more than the condition of the trunk or canopy. The tree, its roots, the soil, its recent management and the targets nearby all affect the level of risk.

Windthrow describes a tree being uprooted by wind, often with its root plate lifting from the ground. It is a common concern after prolonged rain and storms, particularly on exposed sites across East Sussex. It can also develop gradually, with small changes in stability giving early warning before a serious failure.

What makes windthrow a risk?

A tree does not need to be dead to be vulnerable to windthrow. Healthy trees may fail where the ground is waterlogged, rooting space is restricted or the tree has become exposed following changes around it. The question is not simply whether a tree could fall. Almost every tree could fail under exceptional conditions. The practical question is whether it is likely to fail, and what it could strike if it does.

This is why location matters. A leaning tree in a remote part of a woodland may require monitoring or sensitive management, while a similar tree above a driveway, public footpath, building or play area may need a more urgent response. A professional assessment weighs the likelihood of failure against the consequences, rather than assuming that removal is always the answer.

How to assess windthrow risk: the key checks

A visual check from a safe distance can identify reasons to seek advice. Do not approach a tree that has moved in high winds, especially if roots are lifting, branches are hanging or overhead services are nearby. Ground conditions can change quickly and a partially uprooted tree may be under considerable tension.

Look for root plate movement

The root plate is the mass of roots and soil that anchors the tree. Fresh cracks or heaving soil around the base are among the clearest signs that a tree has moved. You may see a raised area of turf or soil on one side, gaps opening on the other, or exposed roots that were previously underground.

Movement of the root plate after a storm should be treated seriously, even where the trunk remains upright. The tree may have lost much of its anchorage and further wind can cause complete failure. Avoid parking, walking or working beneath the canopy until it has been inspected.

Check for a new or worsening lean

Many established trees grow with a natural lean and have adapted their root systems and branch structure over time. A lean is therefore not automatically dangerous. What matters is whether it is recent, increasing or accompanied by soil disturbance, cracks in the trunk, or damaged roots.

Compare the tree with older photographs if possible, or with nearby vertical features such as a fence line or building. A sudden change after wind is more concerning than a long-standing, stable form. Trees at the edge of woodland, on banks or beside recently cleared ground deserve particular attention because they may now be taking wind from a new direction.

Consider the ground and drainage

Saturated ground reduces the resistance available to a root system. Clay soils can soften significantly after prolonged rain, while shallow soils over chalk, rock or compacted ground may limit rooting depth. Poor drainage, leaking pipework and repeated soil disturbance can all contribute to reduced stability.

Recent excavation is especially relevant. Building works, trenching, driveway installation and changes in ground level can sever or bury roots well beyond the visible trunk. Damage may not show immediately. A tree can remain green and appear healthy while its anchorage has been compromised.

Inspect the trunk and crown for imbalance

A tree with substantial decay at the base, a cavity, fungal fruiting bodies or a major split may be less able to withstand wind loading. Dead or broken branches do not necessarily indicate windthrow risk, but they can create a separate hazard during high winds and should be considered as part of the overall inspection.

Crown shape also matters. A large, heavily weighted limb, a dense crown catching the wind, or a canopy extending strongly to one side can increase leverage on the stem and roots. Equally, indiscriminate reduction work can create new problems. The right specification depends on the species, condition, age, setting and wildlife value of the tree.

Think about recent changes around the tree

Trees adapt to their surroundings. Those growing within a group or woodland often develop with shelter from neighbouring trees. If adjacent trees have been removed, died back or failed in a storm, the remaining trees may suddenly be exposed to stronger winds.

This does not mean every newly exposed tree must be pruned or removed. It does mean its condition and position should be reviewed. Selective woodland management can reduce risk while retaining habitat, screening and the long-term character of the site.

Factors that can make a tree more vulnerable

Certain circumstances call for a closer inspection, particularly when several occur together:

• a recent storm has caused a new lean, soil cracking or root lift;

• the tree stands in wet, compacted, shallow or disturbed soil;

• there are signs of decay, basal damage or previous root loss;

• the crown is heavily one-sided or has large overextended limbs; and

• the tree could reach people, buildings, roads, vehicles or neighbouring land if it failed.

These signs are indicators, not a diagnosis. Fungal brackets, for example, vary greatly in significance depending on the fungus, host tree and location of decay. Similarly, a tree with a broad crown may be well adapted to its form. Sound arboricultural judgement is needed to avoid unnecessary work while dealing with genuine risk.

Why professional assessment is often the sensible next step

A qualified arborist can inspect the tree from ground level, identify defects, consider site history and recommend proportionate action. Where needed, this may include a more detailed assessment, climbing inspection or specialist investigation. The aim is to establish what is reasonably foreseeable and what practical measures will reduce risk.

Recommendations may range from monitoring and improving access management to carefully specified pruning, bracing in suitable cases, or removal where no reasonable retention option exists. Work should be planned in accordance with BS 3998:2010 tree work recommendations, which promotes good practice and helps protect the health and structure of retained trees.

For larger sites, estates and commercial premises, a recorded inspection programme is particularly useful. It provides a clear basis for prioritising work, documenting decisions and reviewing trees after severe weather. This is more reliable than reacting only when a branch falls or a tree becomes visibly unstable.

Avoid quick fixes after a storm

Storm damage can create pressure to act immediately, but hasty work may increase risk. Topping a tree or removing large limbs without a clear objective can leave significant wounds, encourage weak regrowth and alter the way the remaining crown responds to wind. It may also fail to address the real issue if the root system is unstable.

Keep people away from the affected area, note any visible changes and arrange an inspection. Never attempt to pull over, winch or cut into a leaning tree without the correct equipment, training and exclusion zone. Trees affected by windthrow can shift unexpectedly, and damaged limbs may be held under load.

Before any major work, check whether the tree is protected by a Tree Preservation Order or stands within a conservation area. Ecological considerations also matter. Nesting birds, bat roost potential and other habitat features should be considered when planning the timing and method of work.

Sensible management protects both people and trees

Assessing windthrow risk is not about treating every mature tree as a problem. Well-managed trees provide shade, habitat, privacy and lasting value to a property or landscape. The best decisions recognise those benefits while addressing clear, site-specific hazards with the least intrusive effective measure.

If a tree has moved, the ground around it is lifting, or you are concerned about its condition near a frequently used area, arrange professional advice promptly. BC Tree Services can provide practical, responsible tree assessments and recommended work for properties, estates and managed sites, helping you make a safe decision before the next period of severe weather.