I need to give you some background on the matter. Surface water runoff is a hotly debated topic and there has been alot of litigation concerning such. Diffused surface water, in its natural state, occurs after rainfall or snowmelt and flows across land from high elevations to lower elevations. This diffused water is often called stormwater, drainage water, or surface runoff.
Once the water flows into a clearly defined watercourse, it is claimed by the state and is subject to appropriation. On its way to the watercourse, drainage water often flows across privately owned lands. In such cases the water does not automatically become the property of the landowners, although they may capture and use it. Legal problems arise when a landowner interferes with the natural flow of drainage water by capturing and holding the flow or by diverting or increasing it. There are four general rules of law that apply when diffused surface water is captured or diverted:
Common Enemy Rule. One is called the "common enemy rule." Under this rule, drainage water is regarded as an enemy common to all landowners. The law allows every owner to take any measure to protect property, regardless of the consequences to other neighbors.
Modified Common Enemy rule. Landowners are not liable for diverting water unless they the block a natural drainway, collect water and channel it, or fail to exercise due care.
Natural Flow or Civil Law Rule. This rule recognizes that each landowner is entitled to rely upon continuation of the natural flow. Under this rule a landowner who increases runoff, thereby causing flooding, is liable for damages.
Reasonable Flow. This rule allows landowners to divert or change drainage water, even to the extent of harming adjoining neighbors, so land as the diverter's actions are "reasonable" considering all circumstances.
Texas follows the natural flow or civil law rule Jefferson County Drainage district No. 6 v. Lower Neches Valley Authority, 876 S.W.2d 940 (Texas 1994). In a landowner who increases runoff, thereby causing flooding is liable for damages.
So, the neighbor is liable to you for damages he caused or causes because he's increasing the runoff and directing such towards your property.
If a neighbor is legally responsible for water damage you suffer, you may be entitled to any or all of the following:
1) compensation for cost of repairs and replacements
2) compensation for expenses such as having to stay at a motel
3) reimbursement for medical expenses
4) compensation for mental distress, if you have suffered an underlying physical injury
punitive damages, if a neighbor acted maliciously.