/**
 * River Generation Module
 *
 * Generates rivers using flow accumulation algorithm.
 * Inspired by Azgaar's river system (reference/AZGAAR_SNAPSHOT.md Section 4).
 *
 * Algorithm:
 * 1. Calculate flow accumulation from precipitation
 * 2. Identify high-flux cells as river sources
 * 3. Trace river paths downhill to ocean/lake
 * 4. Track confluences where rivers merge
 *
 * Key properties:
 * - Deterministic (seedable PRNG)
 * - Rivers always flow downhill
 * - Acyclic network (DAG structure)
 * - Flux increases downstream
 * - Memory optimized using TypedArrays
 */
/**
 * Point in 2D grid
 */
export interface Point {
    x: number;
    y: number;
}
/**
 * Single river with path and flow data
 */
export interface River {
    id: string;
    /** River path from source to mouth */
    path: Point[];
    /** Water flux at each point in path */
    flux: number[];
    /** Points where tributaries join this river */
    confluences: Point[];
}
/**
 * Complete river system for a world
 */
export interface RiverSystem {
    rivers: River[];
    /** Flow accumulation map */
    flowMap: number[][];
}
/**
 * River generation options
 */
export interface RiverGenerationOptions {
    /** Deterministic seed */
    seed: string;
    width: number;
    height: number;
    /** Elevation map (Uint8Array) */
    elevation: Uint8Array;
    /** Precipitation map (optional, defaults to uniform) */
    precipitation?: Float32Array;
    /** Sea level (default 20) */
    seaLevel?: number;
    /** Minimum flux to form a river (default 100) */
    minFlux?: number;
}
export declare const toIndex: (x: number, y: number, width: number) => number;
export declare const fromIndex: (index: number, width: number) => {
    x: number;
    y: number;
};
/**
 * Generate river system
 */
export declare function generateRivers(options: RiverGenerationOptions): RiverSystem;
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