Source: https://www.quantsurv.com/sectors/infrastructure/drainage-and-flood-protection
Content format: Markdown version of the public page.
Content reviewed: 2026-10-13

# Drainage and flood protection

Quantity surveying and claims support for drainage networks, attenuation, outfalls and flood-protection construction.

## Commercial challenges and how we approach them

Drainage and flood-protection schemes can combine pipework, channels, storage features, structures and earthworks. Below-ground construction needs to connect with levels, outfalls and surface works across the site. Quantities and package interfaces need to remain clear where drainage is delivered alongside a wider development or existing assets.

### Outfall levels and existing drainage connections

#### The Challenge

A different outfall level can change the depth of an entire drainage run, not just the connection at its end.

#### Our approach

We compare survey findings and technical instructions with the priced design. The valuation follows the whole affected run, separating additional quantities and temporary measures from allowances already included.

### Temporary flow control during construction

#### The Challenge

Drainage and flood works may need bypass pumping, temporary channels or protection while the permanent system is incomplete. A changed flow or sequence can extend equipment hire and attendance.

#### Our approach

We check the bypass or temporary-flow arrangement included at tender, including its expected duration. Actual flow, plant and instruction records help establish why it remained longer or had to change. A hire invoice proves an expense was incurred; it does not, on its own, show that the other party is responsible for it.

### Earthworks and material suitability

#### The Challenge

Material available on site may not satisfy the engineer's requirements for an embankment. Planned reuse can become a combination of disposal and imported fill, with a very different haulage and testing cost.

#### Our approach

We reconcile the accepted and rejected material with surveys and movements, checking treatment and transport against the excavation and fill rates.

### Seasonal access and environmental working periods

#### The Challenge

River and floodplain construction may be constrained by agreed ecological periods, land access and weather exposure. A delayed start can move activities into a more restrictive period and change the delivery method.

#### Our approach

We identify the actual access or ecological restriction and trace its effect on the affected activities. A seasonal premium needs a demonstrated change in method, attendance or mobilisation behind it.