diff --git a/changelog_unreleased/266-adaptive-lease-time-threshold b/changelog_unreleased/266-adaptive-lease-time-threshold
new file mode 100644
index 0000000000..9802eca838
--- /dev/null
+++ b/changelog_unreleased/266-adaptive-lease-time-threshold
@@ -0,0 +1,7 @@
+[func]		fdupont
+	Added the new "adaptive-lease-time-threshold" parameter
+	for the FLQ (Free Lease Queue) allocator which reduces
+	lifetime of leases when pools of a subnet have an
+	occupancy rate above a configured threshold (new feature
+	from ISC DHCP).
+	(Gitlab #226)
diff --git a/doc/sphinx/arm/dhcp4-srv.rst b/doc/sphinx/arm/dhcp4-srv.rst
index aec25d71c2..a669cff9ba 100644
--- a/doc/sphinx/arm/dhcp4-srv.rst
+++ b/doc/sphinx/arm/dhcp4-srv.rst
@@ -8985,3 +8985,20 @@ avoiding unnecessary impact on the server's startup time.
    As a result, the servers will not be able to offer some of the available
    leases to the clients. Only a server reclaiming a particular lease will
    be able to offer it.
+
+In Kea 3.1 a new parameter ``adaptive-lease-time-threshold`` was added.
+It can be specified at global, shared network and subnet levels and
+takes a floating point value between ``0.`` (excluded) and ``1.``.
+It is disabled by default or when set to ``1.``. It is active only with
+he FLQ allocator and when the occupancy rate of pools of subnet is
+above the specified value the server decreases the lease valid lifetime
+to the applicable ``min-valid-lifetime`` for new clients. Clients
+renewing an already existing lease get at least the remaining lifetime
+from the current lease. Since the leases expire faster, the server may
+either recover more quickly or avoid pool exhaustion entirely.
+
+The occupancy rate is defined as being the number of already assigned
+addresses (including the address being assigned) divided by the total
+number of addresses in pools where the address can be allocated from
+(i.e. if the query is not member of a ``client-classes`` guard of a pool
+this pool is not taken into account).
diff --git a/doc/sphinx/arm/dhcp6-srv.rst b/doc/sphinx/arm/dhcp6-srv.rst
index 268804cf1d..6bf1c1c8d9 100644
--- a/doc/sphinx/arm/dhcp6-srv.rst
+++ b/doc/sphinx/arm/dhcp6-srv.rst
@@ -8730,3 +8730,21 @@ avoiding unnecessary impact on the server's startup time.
    As a result, the servers will not be able to offer some of the available
    leases to the clients. Only a server reclaiming a particular lease will
    be able to offer it.
+
+In Kea 3.1 a new parameter ``adaptive-lease-time-threshold`` was added.
+It can be specified at global, shared network and subnet levels and
+takes a floating point value between ``0.`` (excluded) and ``1.``.
+It is disabled by default or when set to ``1.``. It is active only with
+he FLQ allocator and when the occupancy rate of pools of subnet is
+above the specified value the server decreases the lease valid lifetime
+to the applicable ``min-valid-lifetime`` for new clients. Clients
+renewing an already existing lease get at least the remaining lifetime
+from the current lease. Since the leases expire faster, the server may
+either recover more quickly or avoid pool exhaustion entirely.
+
+The occupancy rate is defined as being the number of already assigned
+delegated prefixes (including the address being assigned) divided by the total
+number of prefixes in pools where the address can be allocated from
+(i.e. if the query is not member of a ``client-classes`` guard of a pool,
+or if the delegated prefix length is not compatible this pool is not taken
+into account).