[WGEN] Different heights problem

I'm trying to generate a entire world out of sand. But I want to have it to have different heights in some biomes. But now I'm getting this:



Is there a way to smooth it?

Code:

public byte[] generate(World world, Random random, int chunkX, int chunkZ) {
        byte[] b = new byte[16*16*128];
        Random seed = new Random(world.getSeed());
        SimplexOctaveGenerator gen =  new SimplexOctaveGenerator(seed, 8);
        gen.setScale(1/40.0);
 
       
        for (int x=0; x<16; x++){
                    for (int z=0; z<16; z++){
                        int multiplier = 10;
                        if(world.getBiome(x+chunkX*16, z+chunkZ*16) == Biome.DESERT ||
                                world.getBiome(x+chunkX*16, z+chunkZ*16) == Biome.DESERT_HILLS ||
                                world.getBiome(x+chunkX*16, z+chunkZ*16) == Biome.EXTREME_HILLS ||
                                world.getBiome(x+chunkX*16, z+chunkZ*16) == Biome.FOREST_HILLS ||
                                world.getBiome(x+chunkX*16, z+chunkZ*16) == Biome.ICE_MOUNTAINS)
                            multiplier = 16;
                        if(world.getBiome(x+chunkX*16, z+chunkZ*16) == Biome.PLAINS ||
                                world.getBiome(x+chunkX*16, z+chunkZ*16) == Biome.ICE_PLAINS ||
                                world.getBiome(x+chunkX*16, z+chunkZ*16) == Biome.TUNDRA)
                            multiplier = 6;
                       
                        double noise = gen.noise(x+chunkX*16, z+chunkZ*16, 0.5, 0.5)*multiplier;
                        for(int y=0; y<32+noise; y++){
                            if(b[xyzToByte(x,y,z)] ==0)
                                if(y == 0)
                                    b[xyzToByte(x,y,z)] = (byte)  (Material.BEDROCK).getId();
                                else
                                    b[xyzToByte(x,y,z)] = (byte)  (Material.SAND).getId();
                        }
                        for(int y=0; y<20; y++)
                        {
                            if(b[xyzToByte(x,y,z)] ==0)
                                b[xyzToByte(x,y,z)] = (byte)  (Material.STATIONARY_WATER).getId();
                        }
                       
                        b[xyzToByte(x,0,z)] = (byte)  (Material.BEDROCK).getId();
                    }
                }
 
        return b;
        }

 

You can using direct the biome temparaturs and rainfall