Problems in generating navmesh for terrain

I am currently trying to create a navmesh for the terrain that is generated using HillHeightMap. The tarrain is 512x512. Then i run the navmeshGenerator(from critterAI library) on the terrain mesh to generate the navmesh. The problem is that the generated navmesh is lacking segments all over the map. This pictures shows what i mean: ||
The critterAI library provides lots of tweaks for the generator but i tried changing them and failed. Mabye the terrain mesh is not suitable for the generator??

The current settings for the generator are:

private float cellSize = 1f;
private float cellHeight = 15f;
private float minTraversableHeight = 0f;
private float maxTraversableStep = 1000f;
private float maxTraversableSlope = 30.0f;
private boolean clipLedges = false;
private float traversableAreaBorderSize = 12f;
private int smoothingThreshold = 0;
private boolean useConservativeExpansion = true;
private int minUnconnectedRegionSize = 1000;
private int mergeRegionSize = 10000;
private float maxEdgeLength = 100;
private float edgeMaxDeviation = 2.4f;
private int maxVertsPerPoly = 3;
private float contourSampleDistance = 25;
private float contourMaxDeviation = 25;