When analyzing a site's topography, which characteristic would be MOST concerning for residential development?
Correct Answer
C) A 25% slope requiring extensive grading
A 25% slope would require extensive and expensive grading, excavation, and potentially retaining walls, significantly increasing development costs. Gentle slopes are actually preferred for drainage purposes.
Why This Is the Correct Answer
A 25% slope represents a severe topographical challenge that would require extensive grading, excavation, and likely retaining walls to create buildable lots. This slope percentage translates to approximately a 1-foot rise for every 4 feet of horizontal distance, making standard construction methods difficult and expensive. The development costs associated with such steep terrain would significantly impact the economic feasibility of residential development and reduce the site's overall value.
Why the Other Options Are Wrong
Option A: A gentle 3% slope toward the street
A gentle 3% slope toward the street is actually ideal for residential development as it provides natural drainage away from structures while remaining easily buildable with minimal grading costs.
Option B: Level terrain with no slope
Level terrain, while requiring minimal grading, may actually present drainage challenges and could require engineered drainage solutions, but this is far less problematic than steep slopes.
Option D: A slight elevation above surrounding properties
Slight elevation above surrounding properties is generally advantageous as it provides natural drainage, better views, and protection from flooding, making it desirable for residential development.
The 25% Slope = 25x Cost Rule
Remember that a 25% slope can cost 25 times more to develop - when you see steep percentages like 25%, think 'expensive problems' and associate high percentages with high costs and high concern levels.
How to use: When you see slope percentages in questions, immediately categorize them: 1-10% = good, 10-15% = manageable, 15%+ = concerning, 25%+ = major problem.
Exam Tip
Look for extreme values in topography questions - gentle slopes (under 10%) are usually positive, while steep slopes (over 20%) typically indicate development challenges and increased costs.
Common Mistakes to Avoid
- -Thinking that perfectly level terrain is always best (it can create drainage issues)
- -Not recognizing that gentle slopes are actually preferred for proper drainage
- -Underestimating the cost impact of steep slopes on development feasibility
Concept Deep Dive
Analysis
Topography analysis is a critical component of site evaluation in real estate appraisal, as it directly impacts development costs, construction feasibility, and property value. Slopes affect drainage patterns, foundation requirements, utility installation, and overall building costs. While some slope is beneficial for proper water drainage, excessive slopes create significant engineering challenges and cost burdens. The key is understanding the threshold where slope becomes a liability rather than an asset, typically when grades exceed 15-20% for residential development.
Background Knowledge
Residential development typically works best with slopes between 1-10%, with 2-5% being optimal for drainage without excessive grading costs. Slopes exceeding 15-20% begin to create significant construction challenges and cost increases.
Real-World Application
In practice, appraisers must consider grading costs when valuing vacant land, as a lot requiring $50,000+ in site preparation due to steep slopes will have significantly less value than a similar lot needing minimal grading work.
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