Reports and investigations

Using historic photographs and information from the past, we are better positioned to know how to reduce the impact of large floods in the future.

Despite considerable investment in structural flood control works, we've noticed a trend of increasing flood losses on Canterbury’s floodplains.

We now know full reliance on structural measures, such as stopbanks, is not cost effective or realistic. We work with the public, territorial authorities and other organisations developing floodplain management plans and strategies for catchments throughout the region.

They highlight flood warnings, public awareness of flooding and civil defence measures that combine to reduce the impacts of large floods on the Canterbury community.

The strategies set recommendations for improving floodplain management and reducing flood risk but it is the technical investigations that provide specific detail.

Technical investigations assess river conditions, enhance understanding of flood risk and assess the feasibility of flood protection works. They improve our understanding of specific river and stream capacities and help us to better assess flood risks in specific areas within Canterbury.

Technical investigations include:

Computer-based modelling of river channel capacity and of out-of-river flood flows.
Investigations into the engineering design of flood protection works.
Investigations into the feasibility and effects of flood protection proposals.
Geomorphic investigations such as mapping the imprints that a river's past flooding has left on a floodplain.
Assessing gravel volumes and bed levels within our braided rivers.

Floodplain modelling

The models are computer-generated simulations of various sized flood events. Models are developed using information on hydrology, floodplain topography, riverbed levels, river capacity and historical records.

The final product is a series of maps showing the flood extent and maximum depths that are expected to occur on the floodplain during various sized floods.

We have carried out modelling projects on many of Canterbury’s river catchments which we review and make additions to as part of our ongoing work.