Legal Question in Civil Litigation in California

Re: Neighboring property floods my home during rainpour

You can't directly seek money from your neighbor's insurance, since the insurer owes a duty to them and not to you. However, you can threaten to sue and see if the insurer will settle quickly to protect its insured. If that doesn't work, you can file a suit and force the carrier to either settle with you or fight the lawsuit. Of course, if it turns out you don't have a winning case, you shouldn't expect a large offer.

You call your neighbors' drainage "inadequate," but this means different things to different people. You will need to prove that the landscaping was done negligently in that they should have known you would be affected this way. Also, if the land has not been altered but is just naturally shaped the way it is, you will have a much harder case to prove. It is also possible that the rainstorm that damaged your home was just so freakishly intense that no reasonable landscaper would -- or, perhaps, even could -- have planned for such a contingency.

I hope this is helpful.