Braided rivers: The land the law forgot

Integrating legal, economic, social, and cultural factors into the well-established models of the topology of braided rivers, along with models of climatic uncertainty to better understand these unique landscape features.

The need and impact

Braided rivers are quintessentially of Aotearoa New Zealand, yet visible from space. They are globally rare, yet capricious in nature. They are topologically, geologically, ecologically, economically, and legally complex.

Changing land use and ownership on the margins of braided rivers are allowing creeping, yet measurable, declines in the resilience of Aotearoa New Zealand’s braided rivers.

We have a strong understanding of physical forces that interact to shape braided rivers, although our models suggest our understanding might be waning in the face of climatic change. Yet our understanding of the legal, economic, cultural, and social factors that shape braided rivers’ ever-shifting bed, banks, and margins is almost non-existent.

Critical to this project is understanding how changes in land use and ownership on the ‘dry’, ever-shifting margins of the braidplains of braided rivers affect the dynamics of the ‘wet’ parts of the braidbeds, and how small changes in the wet-dry intersection affect the landscape. From a landscape perspective, understanding the physics of what happens inside the river without integrating it with what happens on the land surrounding these unique rivers will do little to promote landscape-scale conservation.

Integrating legal, economic, social, and cultural factors into the well-established models of the topology of braided rivers, along with models of climatic uncertainty, we develop integrated modelling of factors in both the wet and dry parts of braidbeds, and enable better understanding of these unique landscape features.

This project works in conjunction with the policy network theory at the science-policy interface project to bridge a gap between environmental science and environmental decisions, maximising the resilience of Aotearoa New Zealand’s braided rivers while respecting cultural and private property rights.

Instead of science aspiring to flow into the policy decisions, a two-way flow will produce a powerful management tool to re-shape braided river governance.

The approach

This study will be the first integration of theory and empirics of changing resource ownership with the studies of the physical dynamism of braided rivers (also known as hydrogeomorphological topology, or morphodynamics). Drawing on Williams et al’s 2016 use of digital elevation models and aerial imagery of floods to develop morphodynamical models, we then integrate these approaches with aerial imagery of changing land use in river margins, cultural mapping of traditional resource use and stewardship (with Ngāi Tahu’s Black Maps project), and regulatory mapping of statutory consents granted to develop land or resources in the river margins.

Using theories and methods of topology, we will combine the wet and the dry, the social and the physical, the regulatory and the hydrological. The topological merging of dialectical datasets will allow exploration of the research question about interactions between wet and dry.

Research aims

Use topological theory and methods to understand the dialectic interactions between land use decisions and the topology of braided river morphology to maximize river resilience (all) (with end-users and partners).

Use topological modelling, incorporating data from geospatial, hydrogeomorphological, and socio-legal realms.

Predict the effect of current lack of legal certainty around boundaries of private ownership and public riverbed on the future shape of braided rivers.

People

• Professor Ann Brower (Project Lead)
• Professor Alex James
• Renate Vosloo
• Connor Fraher
• Aimee Calkin