FindLowerElevation.java

private Coord findLowerElevation(Coord currentLocation, GreasedRegion riverBlockages) {
    GreasedRegion heights = new GreasedRegion(heightData.data, Sand, heightData.data[currentLocation.x][currentLocation.y]);
    GreasedRegion nonBlockedHeights = heights.andNot(riverBlockages);

    int searchDistance = 40;
    int cx = currentLocation.x, cy = currentLocation.y;

    int x = 0, y = 0;
    for(int rx = -searchDistance/2; rx < searchDistance/2; rx++) {
        for(int ry = -searchDistance/2; ry < searchDistance/2; ry++) {
            int dx = cx + rx, dy = cy + ry;
            if(!contains(dx, dy)) continue;
            if(nonBlockedHeights.contains(dx,dy)) return Coord.get(dx,dy);
            y++;
        }
        y = 0;
        x++;
    }
    return null;
    }