Hydrological Analysis – Preliminary Report: Kern County, CA

Hydrological Analysis Report

Generated: 2025-09-08T12:55:18.235380
File: california_kern_20250908_125516.kml

Executive Summary

Location: Unknown, Kern County, California
Flood Zone: AO - High Risk - Special Flood Hazard Area (1% annual chance)
Site Area: 100.0 acres (0.16 sq mi)

Site Location

Site Information

Geographic Data

Center Coordinates: 35.294013, -118.905260
Bounding Box:
North: 35.296878
South: 35.291149
East: -118.901751
West: -118.908770
Dimensions: 0.4 mi × 0.4 mi

Flood Zone Analysis

Primary Flood Zone: AO

Risk Level: High Risk - Special Flood Hazard Area (1% annual chance)
DFIRM Panel: 06029C

Flood Zone Implications

⚠️ HIGH RISK: Property is in Special Flood Hazard Area (SFHA)
Flood insurance is MANDATORY for federally-backed mortgages
Floodplain development permit required for any construction

Precipitation Data

✅ Using ACTUAL NOAA Atlas 14 precipitation data

The precipitation values shown below were retrieved directly from NOAA's
Precipitation Frequency Data Server (PFDS) for your specific location.

Verify data at: https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?lat=35.2940&lon=-118.9053

Location: 35.2940135°, -118.9052605°
Region: Western US
Data Source: NOAA Atlas 14 - Actual Data

Design Storm Summary

Water Quality Volume (WQv) - 1-year, 24-hour storm
Depth: 0.784 inches
Use: BMP sizing for water quality treatment
Channel Protection Volume (CPv) - 2-year, 24-hour storm
Depth: 1.04 inches
Use: Extended detention for channel erosion prevention
Overbank Flood Protection - 10-year, 24-hour storm
Depth: 1.7 inches
Use: Detention sizing for flood mitigation
Extreme Flood Protection - 100-year, 24-hour storm
Depth: 2.85 inches
Use: Emergency spillway and freeboard design

Precipitation Frequency Estimates

Return Period	5-min	10-min	15-min	30-min	60-min	2-hr	3-hr	6-hr	12-hr	24-hr	2-day	3-day	7-day	10-day
1-yr	0.07 in	0.101 in	0.122 in	0.168 in	0.236 in	0.338 in	0.406 in	0.524 in	0.633 in	0.784 in	0.915 in	0.986 in	1.18 in	1.27 in
2-yr	0.089 in	0.128 in	0.155 in	0.213 in	0.299 in	0.424 in	0.509 in	0.661 in	0.817 in	1.04 in	1.22 in	1.32 in	1.6 in	1.72 in
5-yr	0.117 in	0.168 in	0.203 in	0.279 in	0.392 in	0.547 in	0.654 in	0.851 in	1.07 in	1.4 in	1.66 in	1.8 in	2.18 in	2.36 in
10-yr	0.142 in	0.204 in	0.246 in	0.339 in	0.476 in	0.655 in	0.781 in	1.01 in	1.29 in	1.7 in	2.02 in	2.21 in	2.68 in	2.9 in
25-yr	0.18 in	0.258 in	0.312 in	0.429 in	0.602 in	0.815 in	0.967 in	1.25 in	1.6 in	2.13 in	2.55 in	2.79 in	3.4 in	3.68 in
50-yr	0.212 in	0.304 in	0.368 in	0.506 in	0.711 in	0.949 in	1.12 in	1.44 in	1.86 in	2.48 in	2.98 in	3.27 in	3.97 in	4.3 in
100-yr	0.248 in	0.356 in	0.43 in	0.592 in	0.831 in	1.1 in	1.29 in	1.65 in	2.13 in	2.85 in	3.44 in	3.78 in	4.57 in	4.95 in

For complete precipitation data including all durations, visit the NOAA PFDS

Rainfall Intensity (for Rational Method)

10 yr, 5 min: 1.7 inches/hr
25 yr, 5 min: 2.16 inches/hr
100 yr, 5 min: 2.98 inches/hr

Precipitation Visualizations

Intensity-Duration-Frequency (IDF) Curves

Precipitation Summary

100-Year Design Storm Hyetograph

Regulatory Analysis

Jurisdiction-Specific Requirements - Kern, California

Design Storm Requirements:

Residential: 10-year
Commercial: 10-year
Industrial: 10-year
Major Facilities: 100-year
Emergency Overflow: 100-year

Hydrology Method: Rational Method for areas < 640 acres, Unit Hydrograph for larger areas

Runoff Coefficients:

Residential Quarter Acre: 0.55
Residential Half Acre: 0.45
Residential One Acre: 0.35
Commercial: 0.85
Industrial: 0.8
Parks: 0.2
Agricultural: 0.2

Special Requirements:

Retention Basin Freeboard: 2 feet minimum
Detention Basin Freeboard: 1 foot minimum
Emergency Spillway: Required for all retention/detention facilities
Velocity Limits - earth_channels: 4 fps maximum
Velocity Limits - grass_lined: 6 fps maximum
Velocity Limits - concrete_lined: 20 fps maximum
Division Four covers eastern Kern County
Different standards may apply in incorporated cities
Special flood hazard areas require additional analysis

Contact Information:

Public Works: (661) 862-8850
Planning: (661) 862-8600

Reference Documents:

Kern County Division Four Standards for Drainage.pdf
KCHydrologyManual.pdf
Kern County Grading Code 3574 downloads.pdf

Jurisdictional Overview

Federal: FEMA, USACE (if wetlands present)
State: California
County: Kern
City: Unincorporated area

Permit Requirements

Research conducted: 2025-09-08T12:55:18.857051

SITE-SPECIFIC HYDROLOGICAL REQUIREMENTS FOR 100.0-ACRE SITE IN ZONE AO, KERN COUNTY, CALIFORNIA

1. STATE-LEVEL PERMIT REQUIREMENTS

California Environmental Protection Agency (CalEPA)

State Water Resources Control Board (SWRCB)

Construction General Permit (CGP): REQUIRED for this 100-acre site
Order No. 2022-0057-DWQ
Threshold: Projects disturbing ≥1 acre (YOUR SITE QUALIFIES)
Risk Level Determination: Likely Risk Level 2 or 3 based on 100-acre size
Submit through SMARTS database: https://smarts.waterboards.ca.gov
Filing fee: $1,775 (Risk Level 2) or $2,625 (Risk Level 3) as of 2024
Annual fee: $1,450 (Risk Level 2) or $2,025 (Risk Level 3)
Timeline: 7-14 days for NOI processing after complete submittal

Professional Certifications Required:

Qualified SWPPP Developer (QSD) - REQUIRED for Risk Level 2 or 3
Qualified SWPPP Practitioner (QSP) - REQUIRED during construction
Professional Engineer (PE) - NOT required by state for SWPPP

401 Water Quality Certification:

Required IF federal permits (404) are needed
Central Valley Regional Water Quality Control Board (Region 5)
Application fee: Based on project impacts (typically $1,000-$10,000)

2. LOCAL PERMIT REQUIREMENTS

Kern County Specific Permits for 100-Acre Site:

Grading Permit - REQUIRED

Kern County Code Chapter 17.48
Form: Available at Kern County Engineering, Surveying & Permit Services
Threshold: >50 cubic yards OR >5,000 sq ft (YOUR SITE QUALIFIES)
Fee: Based on volume - approximately $5,000-$15,000 for 100 acres
Submittal: 3 sets of plans at 1"=40' or 1"=50' scale

Floodplain Development Permit - REQUIRED for Zone AO

Kern County Code Chapter 16.80
Form: FP-1 Floodplain Development Permit Application
Fee: $500 base + $100/acre over 5 acres = $10,000 for 100 acres
Review timeline: 30-45 days

Drainage Study - REQUIRED

Required for projects >10 acres per County standards
Must analyze 100-year storm event
Professional Engineer stamp required

3. PERMIT SEQUENCING AND COORDINATION

Required Sequence:

Kern County Floodplain Development Permit (FIRST - before any other permits)
Kern County Grading Permit
State CGP Coverage (NOI filed before earth disturbance)
Building permits (require proof of CGP coverage)

Coordination:

County reviews drainage/grading concurrent with floodplain permit
State CGP is independent process through SMARTS
Total timeline: 60-90 days for complete permit package

4. TECHNICAL CALCULATIONS

State Requirements (CGP):

2-year, 24-hour storm for Risk Level 2 & 3 erosion control
Water Quality Design Storm: 85th percentile storm

Kern County Requirements for 100-Acre Site:

Design Storm: 100-year, 24-hour event
Precipitation Data:
NOAA Atlas 14 values ARE ACCEPTED with local adjustment
100-year, 24-hour: 2.85 inches × 1.1 adjustment factor = 3.14 inches
Must use Kern County Hydrology Manual adjustment factors
Storm Distribution: SCS Type II (24-hour)
Methodology: Modified Rational Method acceptable up to 640 acres
Software: HEC-HMS or HEC-RAS accepted
Time of Concentration: Kirpich or SCS method per County Manual
Runoff Coefficient: Per Table 3-1 Kern County Hydrology Manual

5. DESIGN STANDARDS

Critical Zone AO Requirements:

FREEBOARD REQUIREMENTS:

FEMA Minimum: 1 foot above highest adjacent grade + depth number
Kern County Requirement: 2 FEET above BFE per Chapter 16.80.140
For Zone AO specifically: 2 feet above highest adjacent grade PLUS the AO depth number (1-3 feet shown on FIRM)
Local requirement EXCEEDS FEMA minimum: YES
Source: Kern County Code Section 16.80.140(A)(3)

Zone AO Specific Design:

Shallow flooding with depths 1-3 feet
Design for sheet flow conditions
Drainage must maintain existing flow patterns
No obstruction to sheet flow allowed

Detention Requirements for 100-Acre Site:

Post-development peak ≤ pre-development for 10-year and 100-year storms
Detention volume: Calculated per County Hydrology Manual
Emergency spillway required for 100-year event
Freeboard: 2 feet minimum in detention basins

6. SUBMITTAL DETAILS

State CGP Submittal:

Electronic only through SMARTS
SWPPP uploaded as PDF
Risk Level determination worksheet
Site maps showing BMPs
QSD certification

Kern County Submittal for 100-Acre Site:

Grading Plans: 3 sets at 1"=50' scale
Drainage Report: Stamped by PE
FEMA Elevation Certificate: For Zone AO structures
Digital Format: PDF for all documents, AutoCAD (.dwg) for plans
Review Timeline: 30 days first review, 15 days resubmittal

7. STATE AGENCY CONTACTS

NOTICE: Contact information provided below should be verified as current

State Water Resources Control Board

Main Office: (916) 341-5250
SUGGESTED SEARCH: "California SWRCB Construction General Permit"
SMARTS Help Desk: (866) 563-3107 [VERIFY CURRENT]

Central Valley Regional Water Board (Region 5)

Fresno Office (covers Kern County): (559) 445-5116 [VERIFY CURRENT]
SUGGESTED SEARCH: "Central Valley Water Board Region 5 Fresno"

8. LOCAL CONTACTS AND RESOURCES

NOTICE: Please verify all contact information as current

Kern County Floodplain Manager

Engineering, Surveying & Permit Services
SUGGESTED SEARCH: "Kern County Floodplain Management"
Address: 2700 M Street, Suite 250, Bakersfield, CA 93301

Kern County Public Works

Main Number: (661) 862-5000 [VERIFY CURRENT]
SUGGESTED SEARCH: "Kern County Public Works permits"

Key Resources:

Kern County Hydrology Manual: Search "Kern County Hydrology Manual current edition"
Development Standards: Available at Kern County Engineering website
Fee Schedule: Updated annually, verify current rates

CRITICAL ITEMS FOR 100-ACRE ZONE AO SITE:

2-foot freeboard requirement (exceeds FEMA minimum)
Sheet flow preservation required in Zone AO
Drainage study by PE required for 100 acres
Use adjusted NOAA precipitation (×1.1 factor)
Both state CGP and local permits required
QSD/QSP certifications mandatory for state permit
Floodplain permit must be obtained FIRST

Additional Jurisdictional Information

HYDROLOGICAL PERMITTING REQUIREMENTS - KERN COUNTY, CALIFORNIA

1. STATE-LEVEL REGULATORY AGENCIES

Primary State Environmental Agency:

California Environmental Protection Agency (CalEPA)
State Water Resources Control Board (SWRCB) - primary water quality authority
Regional Water Quality Control Board - Central Valley Region (Region 5) covers Kern County

Stormwater Management Program:

California has a comprehensive Stormwater Program under SWRCB
National Pollutant Discharge Elimination System (NPDES) delegated to state
Construction General Permit (CGP) Order No. 2022-0057-DWQ
Industrial General Permit (IGP) Order No. 2014-0057-DWQ

State-Level Permits Required:

Construction General Permit (CGP) for projects ≥1 acre
Industrial General Permit (IGP) for industrial facilities
MS4 Permits (Kern County has areas under Phase II MS4)
401 Water Quality Certification for federal permits
Waste Discharge Requirements (WDRs) for non-federal waters

State Wetland Protection:

Porter-Cologne Water Quality Control Act protects "Waters of the State"
Broader than federal jurisdiction - includes isolated wetlands
State Wetland Definition and Procedures (2019)

2. STATE REGULATORY REQUIREMENTS

Construction Stormwater Permits:

CGP required for land disturbance ≥1 acre
Linear Underground/Overhead Projects (LUPs) have separate requirements
Risk-based approach with three risk levels (1, 2, and 3)

BMP Design Standards:

California Stormwater Quality Association (CASQA) BMP Handbooks
CGP requires specific minimum BMPs based on risk level
Post-construction requirements through MS4 permits and local ordinances

Professional Certifications:

Qualified SWPPP Developer (QSD) required for Risk Level 2 & 3 projects
Qualified SWPPP Practitioner (QSP) required for implementation
Professional Engineer not always required for SWPPP

Unique State Requirements:

Numeric Effluent Limitations (NELs) for pH and turbidity (Risk Level 3)
Rain Event Action Plans (REAPs) required
Active Treatment Systems (ATS) allowed with specific requirements

3. COUNTY/LOCAL REGULATORY STRUCTURE

Kern County Departments:

Kern County Public Works Department - Floodplain Management
Kern County Engineering, Surveying & Permit Services
Kern County Environmental Health Services Department

Specific Ordinances:

Chapter 16.80 - Floodplain Management Ordinance
Chapter 17.48 - Grading Ordinance
Chapter 19.98 - MS4 Stormwater Management and Discharge Control

City vs County:

City of Bakersfield has separate MS4 permit and requirements
Smaller cities may defer to County standards
Unincorporated areas follow County requirements

4. UNIQUE LOCAL REQUIREMENTS

Kern County Specific Requirements:

Grading permits required for projects >50 cubic yards or >5,000 sq ft
Drainage studies required for subdivisions and certain commercial projects
Retention/detention basins must handle 100-year storm event
First flush capture requirements in certain areas

Design Standards:

Kern County Development Standards (latest edition)
Hydrology Manual specific to Kern County
Local rainfall data must be used (not generalized state data)

Software Requirements:

Rational Method acceptable for areas <640 acres
HEC-HMS or similar for larger watersheds
AutoCAD Civil 3D commonly required for plan submittal

5. STATE-LOCAL INTERACTION

Permit Sequencing:

Local grading permit typically obtained first
State CGP coverage before earth disturbance
Building permits may require proof of CGP coverage

Coordination:

County enforces minimum state standards
Local requirements often more stringent
County is Local Enforcement Agency (LEA) for some state programs

6. TECHNICAL STANDARDS

Storm Event Analysis:

State: CGP requires 2-year, 24-hour storm for Risk Level 2 & 3
County: 10-year design storm for local drainage
County: 100-year storm for major facilities and floodplain analysis

Detention/Retention Standards:

Post-development peak flow ≤ pre-development (County)
85th percentile storm capture for water quality (MS4 areas)
Specific volume calculations per County Hydrology Manual

Runoff Coefficients:

Kern County has specific coefficients for local soil types
Must account for high clay content in valley areas
Desert areas have different requirements than valley floor

7. KEY DOCUMENTS TO REFERENCE

State Documents:

Construction General Permit Order 2022-0057-DWQ
CASQA BMP Handbooks
State Water Board's SMARTS database guides

County Documents:

Kern County Development Standards
Kern County Hydrology Manual
Kern County Grading Ordinance (Chapter 17.48)
MS4 Permit and Management Plan
Standard Drawings and Specifications

What Would Surprise Out-of-State Engineers:

Dual Jurisdiction for Waters: California regulates "Waters of the State" beyond federal jurisdiction
Risk-Based CGP: Three risk levels with increasing requirements, including numeric limits
QSD/QSP Requirements: Specific state certifications required, not just PE
Active Treatment Systems: Allowed but heavily regulated for construction sites
SMARTS Database: All CGP documentation submitted electronically
Dry Weather Restrictions: Year-round discharge prohibitions, not just wet season
Post-Construction Requirements: Stringent LID requirements even in arid Kern County
Local Soil Conditions: Unique requirements for expansive soils and percolation rates
Agricultural Interface: Special considerations for agricultural discharge and return flows
Drought Considerations: Water conservation requirements affecting stormwater design

Recommended Next Steps

Verify Flood Zone: Confirm flood zone designation with local floodplain administrator
Survey Requirements: Obtain professional survey with elevation data
Preliminary Consultation: Meet with local planning/permitting department
Engineering Analysis: Engage qualified engineer for required studies
Permit Applications: Prepare and submit required permit applications

Data Sources

Location Data: OpenStreetMap Nominatim
Flood Zone Data: FEMA NFHL (public MapServer)
Precipitation Data: NOAA Atlas 14 Precipitation Frequency Data Server
Analysis Date: 2025-09-08 12:57:04

This report is for preliminary analysis only. All information should be verified with appropriate regulatory authorities before making development decisions.