GCSE Edexcel Geography: Formulas and Theorems Quick Reference Handbook | GCSE Edexcel 地理：公式定理速查手册

📚 GCSE Edexcel Geography: Formulas and Theorems Quick Reference Handbook | GCSE Edexcel 地理：公式定理速查手册

This quick-reference handbook compiles essential formulas, calculations, and key theoretical models required for GCSE Edexcel Geography. From river discharge to population change, map skills to urban land use models, you will find clear explanations and paired examples to help you master quantitative and conceptual skills. Whether for fieldwork, exam calculations, or understanding geographic patterns, keep this guide close at hand.

本速查手册汇编了 GCSE Edexcel 地理所必需的关键公式、计算方法和重要理论模型。从河流流量到人口变化，从地图技能到城市土地利用模型，这里提供了清晰的解释和配对示例，帮助你掌握定量和概念性技能。无论是野外调查、考试计算还是理解地理格局，请随身使用这份指南。

1. River Hydrology Formulas | 河流水文学公式

Discharge (Q) is the volume of water passing a point in a river per unit time. It is fundamental for understanding flood risk and channel efficiency.

流量 (Q) 是单位时间内通过河流某点的水量。它对于理解洪水风险和河道效率至关重要。

Q = A × V

where Q is discharge (m³/s or cumecs), A is cross-sectional area (m²), and V is mean velocity (m/s).

其中 Q 为流量（m³/s 或立方米每秒），A 为过水断面面积（m²），V 为平均流速（m/s）。

Cross-sectional area of a regular channel can be simplified as width multiplied by mean depth.

规则河道的过水断面面积可以简化为河宽乘以平均水深。

A = Width × Mean Depth

Measured velocity using a float gives average surface velocity. True mean velocity is about 0.8–0.9 of surface velocity.

使用浮标测得的流速为表面平均流速。实际平均流速约为表面流速的 0.8–0.9 倍。

V = Distance ÷ Time

where distance is the float path length (m) and time is in seconds (s). For an orange or float, multiply by 0.85 to estimate mean velocity in the field.

距离为浮标路径长度（米），时间为秒。野外测量时可将浮标速度乘以 0.85 来估算平均流速。

River gradient describes the slope along the channel profile, usually expressed as a ratio or percentage.

河流比降描述沿河道纵剖面的坡度，通常以比率或百分比表示。

Gradient = Vertical Drop (m) ÷ Horizontal Distance (m)

Example: If a river falls 5 metres over a horizontal distance of 200 metres, the gradient = 5 ÷ 200 = 0.025 (or 1:40).

实例：若某河流水平距离 200 米内落差 5 米，则比降 = 5 ÷ 200 = 0.025（或 1:40）。

2. Demographic Formulas | 人口统计公式

Crude Birth Rate (CBR) indicates the number of live births per 1000 people in a year.

粗出生率 (CBR) 表示一年内每千人的活产婴儿数。

CBR = (Number of Live Births ÷ Total Population) × 1000

Crude Death Rate (CDR) is the number of deaths per 1000 people per year.

粗死亡率 (CDR) 是每年每千人的死亡人数。

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