A national-scale high-resolution runoff risk and channel network mapping workflow for diffuse pollution management

Area of Science:

• Environmental Science
• Hydrology
• Agricultural Science

Background:

• Diffuse pollution from agricultural land necessitates spatially explicit risk assessment.
• Accurate mapping of channel networks and Hydrologically Sensitive Areas (HSAs) is crucial for managing this pollution.
• Complex topography and modified landscapes pose challenges to existing assessment methods.

Purpose of the Study:

• To develop a transferable national-scale workflow for mapping drainage networks and HSAs.
• To create high-resolution risk maps for diffuse pollution management in agricultural areas.
• To deliver targeted risk information to farmers for improved land management practices.

Main Methods:

• Utilized a commissioned LiDAR survey for a national-scale analysis.
• Developed a novel automated drainage channel correction process combined with manual mapping.
• Defined in-field HSAs using a Soil Topographic Index (STI) system incorporating hillslope, contributing area, and soil hydraulic models.

Main Results:

• Created a high-resolution national drainage network, increasing channel density from 0.9 to 5.5 km/km².
• Identified 249 km² of runoff risk HSAs by modeling the top 95th percentile of STI.
• Delivered targeted diffuse pollution risk maps to over 13,000 farmers.

Conclusions:

• The developed workflow provides an unparalleled high-resolution national drainage network and HSA mapping.
• Targeted risk maps are effective tools for farmers in managing diffuse pollution.
• This approach supports nationwide soil and nutrient health management programs.