Stormwater - Urban Roading & Rural

On this page you can find out information about our roading and rural stormwater.

Urban stormwater

Stormwater from our roading network is dealt with in two ways - swales and kerb and channel.


Where there is no kerb and channel, stormwater is often collected in a swale on the berm of the road. From there it either drains away into the ground or to a drain or a ditch. Sometimes the swales are connected by culverts under driveways. When there is heavy rain, ponding occurs in the swale and then drains away after the weather clears.

During periods of prolonged rain or wet weather the ponding can remain for several days, but it will begin to recede after the weather has cleared.

Kerb and channel

Stormwater from the road is channelled to a nearby stormwater catch-pit. You may have seen a catch-pit near a road, with a grid over it for safety and to prevent large debris from blocking it. The catch-pit allows sediments in the water to settle before clearer stormwater flows away in a pipe to a stream or a ditch.

During a heavy downpour the channel can become flooded, but as the water drains away from the catch-pit the water level above it will reduce – this process can take some time. Alternatively, the stormwater drains to a sump and is then pumped to the beach or river – this is once again due to our very flat conditions.

To prevent floodwaters from feeding back into the stormwater network and flooding properties, one-way flap valves are used. The valves do cause ponding which recedes when the rain event stops, and the water level drops.

Rural stormwater

Most roadside drains in Horowhenua are managed by Council, however rural drainage schemes are operated by Horizons Region Council, which is responsible for rural drainage, stop-banks and rivers.

You can find out more about the work of Horizons Regional Council by visiting