How to find drainage problems on a golf course with elevation data.

Map where the course is wet. Trace the flow paths that lead there. Look for the places where water has nowhere to go. Then sort each wet area into one of two kinds: wet because water arrives and cannot leave, or wet where the surface says it should be dry.

The first kind is a surface problem and the elevation data shows you its shape. The second kind points below the surface, to a drain, a leak, or the soil.

Begin with what the crew already knows: standing water after rain, soft ground that ruts under a mower, turf that thins out every wet season, bunkers that hold water. Put each one on a map at its real position.

A shared map matters more than it sounds. A wet area described in a text message moves a little every time it is retold.

A flow-path map, computed from elevation data, shows the line runoff takes downhill and how much ground drains into each line. Follow the paths uphill from each wet area.

A wet spot at the end of a long flow path is collecting water from a large area. The fix may be well upstream: intercepting the flow before it arrives is often cheaper than draining it after.

Three shapes in the terrain account for most surface drainage trouble.

Now compare the two maps. Where the wet areas line up with flow paths and low spots, the terrain explains the problem, and regrading, a swale, or a surface inlet is the kind of fix to cost.

Where an area is wet but the surface shows water running away from it, look underground. The usual causes are a blocked or collapsed drain line, a leaking irrigation line or head, a seep, or soil that will not let water through: compaction, a thatch layer, or heavy clay.

The reverse case is useful too. A place where the terrain says water should collect, but which stays dry, usually has a drain that works. Mark it, so nobody buries the inlet.

An elevation model is the shape of the surface on the day it was captured. It does not know about pipes, catch basins, or soil, and a model made from drone photographs shows tree canopy and tall grass where they hide the ground. Our guide to photogrammetry and LiDAR explains that limit.

So walk the shortlist after rain. Check that each outlet runs, probe the soft areas, and look for the things a model cannot see. Use the model to decide where to walk, and the walk to decide what to build.

A Course Correct twin carries the layers this method needs: water flow paths graded from minor runs to main channels, slope classes from under 2% to over 10%, 0.5 m contours, and a wet-areas layer on the aerial map. See slope and drainage mapping.

Wet areas go on the same model as pinned issues, with a photo and an owner, and the cross-section tool draws the fall along a proposed drain line. The layers are indicative, not survey-grade, so have engineered drainage design checked against a licensed survey.