FindLowerElevation.java

private Coord findLowerElevation(Coord currentLocation, GreasedRegion riverBlockages,
                                 GreasedRegion heights, GreasedRegion reuse, GreasedRegion temp) {
    heights.refill(heightData.data, Sand, heightData.data[currentLocation.x][currentLocation.y])
        .andNot(riverBlockages);

    reuse.clear().insert(currentLocation);
    temp.remake(reuse).fringe();
    int searchDistance = 40;
    for(int d = 1; d < searchDistance; d++)
    {
        if(temp.intersects(heights))
        {
            return temp.singleRandom(CommonRNG.getRng());
        }
        temp.remake(reuse.expand()).fringe();
    }
    return null;
    }